CC SR 20180807 02 - PB Landslide Feasibility Study UpdateRANCHO PALOS VERDES CITY COUNCIL MEETING DATE: 08/07/2018
AGENDA REPORT AGENDA HEADING: Regular Business
AGENDA DESCRIPTION:
Consideration and possible action to receive the Update to the Feasibility Study to
remediate the Portuguese Bend Landslide, and to provide direction to begin
implementing recommendations from the Feasibility Study.
RECOMMENDED COUNCIL ACTION:
(1) Receive and file the Feasibility Study Update;
(2) Appropriate $260,000 and authorize Staff to develop a Request for Proposals for
an engineering analysis, evaluation, and design for the lower portion of the
landslide that would convey the drainage runoff to the ocean directly; as well as
design of groundwater extraction horizontal drains (hydro-augers) for this lower
area of the landslide;
(3) Appropriate $150,000 and authorize Staff to develop a Request for Proposals for
performing a hydrologic study and engineering analysis of the canyons to identify
where, how, and to what extent the stormwater infiltrates into the groundwater in
the Portuguese Bend Landslide Complex; and
(4) Authorize the City Council to appoint a subcommittee to work with the City
Manager and City Attorney in negotiating with the City of Rolling Hills to address
and resolve the runoff as well as sanitary sewer effluent for septic tanks and
private treatment systems which are contributing to landslide movement from the
City of Rolling Hills.
FISCAL IMPACT: Funds for these recommendations have not been included in the
FY18-19 budget.
Amount Budgeted: $0
Additional Appropriation: $410,000
Account Number(s): 330-400-8304-8001
ORIGINATED BY: Ron Dragoo, PE, Principal/City Engineer
Elias Sassoon, PE, Director of Public Works
REVIEWED BY: Gabriella Yap, Deputy City Manager
APPROVED BY: Doug Willmore, City Manager
ATTACHED SUPPORTING DOCUMENTS:
A. January 16, 2018, Staff Report Feasibility Study Update (page A-1)
B. Final Feasibility Study Update (page B-1)
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BACKGROUND AND DISCUSSION:
The City Council’s Subcommittee conducted its most recent public workshop regarding
the Feasibility Study (FS) Update on June 28, 2018, where the consultant, D.B.
Stephens & Associates (DBS&A), provided a summary of the FS and answered
residents’ questions. The remedies presented included subsurface dewatering,
stormwater control, engineered slope stabilization measures, and eliminating septic
system discharge into the landslide.
A primary concern expressed by residents was that any work being conducted within
the preserve could negatively impact habitat and sensitive vegetation. Additionally, a
concern expressed at that meeting was that any of the proposed improvements should
be addressed one at a time and with continuing input from the community.
To that end, Staff recommends starting at the beginning of the list of proposed remedies
recommended in the FS. Upon the design of the new drainage system, the installation
of this system would eliminate any existing ponds which have been created over the
years due to land settlement and/or relocation of pipes/culverts. The installation of
horizontal groundwater extraction wells (hydro-augers) would provide passive
dewatering without the requirement of surface mounted equipment. The hydro-augers
would be installed in the face of the bluff at the ocean, and extend to a predetermined
position in the landslide to collect ground water. Engineering and data are required for
this option to be successful. Accordingly, Staff is requesting funds be appropriated to
allow this work to begin ($260,000). Once a budget is available, Staff will draft an RFP
to obtain the engineering support needed to establish the necessary data to allow
strategic placement of the directional subsurface drains at the bluff to begin the
dewatering process. Any recommendations to award a professional services contract
will be brought back to the City Council for approval prior to authorizing any work to
begin.
Additionally, Staff recommends the appropriation of $150,000 for a proposed study of
the canyons in the upper portion of the landslide to ascertain the extent of runoff from
these canyons contributing to the landslide. This information is needed prior to
performing any work that may facilitate minimizing percolation of runoff into the
landslide through the mass amounts of runoff that are transmitted through the natural
canyons during rain events.
Finally, Staff is recommending that the City Council appoint a subcommittee to work
with the City Manager and City Attorney to negotiate with the City of Rolling Hills to
address and resolve the drainage that contributes to the ground water in the landslide,
as well as addressing the sanitary sewer effluent from septic tanks and private
treatment systems in the City of Rolling Hills that are contributing to landslide
movement.
If Staff’s recommendations are approved, a Subcommittee could begin working toward
negotiations with the City of Rolling Hills as soon as possible. Work on the RFPs would
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also commence right away. This would enable the remedies recommended through the
FS to address the land movement in Portuguese Bend to be underway as early as this
fall.
ALTERNATIVES:
In addition to the Staff recommendations, the following alternative actions are available
for the City Council’s consideration:
1. Identify any issues of concern with the Draft FS, and provide City Staff and
DBS&A with direction in modifying the document.
2. Take no action.
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RANCHO PALOS VERDES CITY COUNCIL MEETING DATE: 01/16/2018
AGENDA REPORT AGENDA HEADING: Regular Business
AGENDA DESCRIPTION:
Consideration and possible action to review and approve the Draft Feasibility Study to
remediate the Portuguese Bend Landslide.
RECOMMENDED COUNCIL ACTION:
(1) Review the Draft Feasibility Study and provide input on the Consultant’s
recommended landslide remediation measures; and,
(2) Direct Staff to finalize the Draft Feasibility Study for adoption at the February 6,
2018, meeting.
FISCAL IMPACT: Expected construction costs to implement the Feasibility Study will
be determined at the time engineering plans are prepared and a Request for Proposals
is issued.
Amount Budgeted: N/A
Additional Appropriation: N/A
Account Number(s): N/A
ORIGINATED BY: Ara Mihranian, AICP, Director of Community Development
Elias Sassoon, PE, Director of Public Works
Deborah Cullen, Director of Finance
REVIEWED BY: Gabriella Yap, Deputy City Manager
APPROVED BY: Doug Willmore, City Manager
ATTACHED SUPPORTING DOCUMENTS:
A. Draft Feasibility Study (page A-1, available at
http://www.rpvca.gov/DocumentCenter/View/11272)
B. Revised Conceptual Work Area Site Plan (page B-1)
C. Public Workshops Summary Notes (page C-1)
D. Section 5 of the Draft NCCP (page D-1)
E. Public Comments (page E-1)
BACKGROUND AND DISCUSSION:
In the spring of 2017, the City Council appointed Mayor Pro Tem Jerry Duhovic and
Council Member Ken Dyda to a subcommittee to identify possible solutions or strategies
to remediate the Portuguese Bend (PB) Landslide. This subcommittee was formed to
begin a collaborative process with community stakeholders and (possibly) with
professional experts.
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In order to provide a forum for stakeholder involvement, the City Council convened a
Committee of concerned residents to chart a path towards achieving stabilization of the
PB Landslide. The Committee identified one of its top priorities as “a complete
characterization of the hydrology of the area.”
Public Workshops on Remediating the PB Landslide
A series of four (4) public workshops were held to elicit the best ideas of the community,
and to seek input on goals and possible solutions to remediate the PB Landslide. The
workshops were held in the evenings (6:00 PM) at Hesse Park, and public notification
was provided via the City’s website, the “Breaking News” listserv, and the City’s
Nextdoor and Facebook pages. Approximately 20 to 30 residents attended these
workshops and participated in the process. Each of the workshops focused on a
specific topic as summarized below (summary notes from each workshop are include as
Attachment C):
• Public Workshop No. 1 held on June 1, 2017 - Identifying Goals
At this first community workshop, a short introduction was provided by Council Member
Dyda and Mayor Pro Tem Duhovic, who outlined the process. During this workshop,
the following three (3) major goals were identified, along with potential solutions relating
to the landslide (also referred to as “landflow”) that might need to be considered in the
series of meetings to follow.
1. Control slide and control costs:
• Decrease the cost of ongoing road repair
• Decrease resident inconvenience
• Decrease cost of slowing slide
• Home stabilization
• Eliminate the danger of the City being “cut in 2” by the loss of the Palos
Verdes Drive South
• Retain Palos Verdes Drive South
• Restore ecology/geology (ocean & land)
• Preserve ocean life/tide pools
2. Legal protection
• Explore possible geological hazard abatement district to protect City from
costly and hazard-related damages
• Avoid a liability situation similar to Palos Verdes Estates landslide
• Understand legal protection upfront
3. Protect the integrity of the nature preserve
• Oceanic and Land Ecosystems
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At this first workshop, the desired result was to structure a design-build Request for
Proposals (RFP) to solicit Federal funding for contracting companies to provide cost vs.
options for success in their responses, as well as the following:
1. Project study report by professional experts;
2. Create community consensus
• Public Workshop No. 2 held on June 20, 2017 – Surface and Subsurface W ater
Runoff
This public workshop focused on eliciting community input on major potential solutions
and actions to intercept water runoff from permeating the ground. The discussion that
ensued at this workshop was wide-ranging, and emphasized on the following:
1. The need to fully understand the hydrology of the watershed within the
Portuguese Bend area;
2. The need to re-establish and maintain an effective storm water control system;
3. The importance of capturing and controlling water runoff before it permeates into
the PB Landslide; and,
4. To minimize impacts to the Palos Verdes Nature Preserve
The attendees at this workshop listed their objectives and voted on what was of greatest
importance to them, as reflected in the attached summary notes.
• Public Workshop No. 3 held on June 29, 2017 - Surf-zone erosion
This public workshop began with an introduction by Councilmember Dyda and there
was a brief power point presentation given by Ray Mathys. The presentation centered
on building a buttress at the toe of the slide that would eventually, over time, stop the
movement, thereby eliminating the sediment from entering the ocean. Additionally,
there was discussion regarding wave action and reef barriers. Consensus of the
participating public focused on the following:
1. Hiring competent engineers to implement recommendations;
2. Early communication with relevant regulatory agencies (e.g., Coastal
Commission) regarding any remediation plans that impacts the City’s Coastal
Zone;
3. Use of road maintenance funds to underwrite the necessary technical work
needed to remediate the PB Landslide; and,
4. Conduct an assessment of the environmental impacts that remediation work
would have on the Palos Verdes Nature Preserve and ocean ecology
• Public Workshop No. 4 held on July 6, 2017 – Ground Water.
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This public workshop focused on major actions that could be considered as a means of
addressing the PB Landslide. As with previous workshops, the public consensus
focused on the following:
1. Understanding the hydrology of the PB Landslide;
2. Understanding the occurrence of groundwater as it relates to the movement of
the PB Landslide; and,
3. Understanding and completing previous work of surface drainage
Pursuant to these workshops, the City Council subcommittee and attendees identified
that hiring a competent coastal engineer to perform a landslide remediation feasibility
study with a full hydrology study of the area was an important next step because expert
testimony and data are essential to moving on to the next step. A number of studies of
the PB Landslide have been conducted over the years, but none recently. Those
studies have generally indicated that slope stability could potentially be achieved
through some combination of surface water capture and infiltration control, groundwater
extraction/dewatering, mass regrading, reinforcement of the landslide toe, and shoreline
erosion control.
The City desires to develop a comprehensive program that will ultimately result in
stabilizing the extensive landslide complex that exists in the Portuguese Bend area. The
program that the City envisions will use information presently available to characterize,
as completely as possible, the hydrology of the landslide area. Using this
characterization, and at the direction of the City Council subcommittee and the public in
attendance at this past summer’s public workshops, Staff was directed to identify a
consultant that had the combination of specialized skills needed to assist the City with
remediating the PB Landslide.
A proposal was requested from the firm Daniel B. Stephens & Associates (DBS&A), Inc.
because they have expert staff and are highly qualified. Additionally, their staff had
attended the workshops prior to the engagement just to familiarize themselves with the
project. The DBS&A team offers a wealth of expertise and experience in conducting
hydrologic, geological, and engineering investigations and landslide stabilization
projects. They specifically built a team to provide the City with unique expertise in
groundwater hydrology, surface water hydrology, engineering geology, and
geotechnical engineering. The team has high-level technical credentials and credibility.
With this strong academic and applied science background, their staff has the ability to
make intelligent and expeditious decisions in the field and prepare clear and defensible
reports of findings and recommendations. The direction from the Subcommittee and
City Council was to develop practical, workable solutions to remediate the PB landslide
complex that will be well-received by the public and in the possible funding application
review process. Because sources impacting the PB Landslide extend beyond the City
limits, the direction given to Staff and DBS&A was to create a plan without being
restrained by jurisdictional boundaries.
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PB Landslide Remediation Draft Feasibility Study
The specific purpose of the Draft Feasibility Study is to identify and select a conceptual
solution that will accomplish the following overall project goals:
• Provide the geotechnical conditions that reduce the risk of damage to public and
private property and would allow for the significant improvement of roadway
infrastructure, safety, and stability.
• Significantly reduce human health risk and improve safety in the City.
• Significantly reduce sediment deposition into the Pacific Ocean that is causing
unacceptable turbidity in the coastal and marine environment.
• Make all reasonable efforts to identify a remedy which will be consistent with the
NCCP and the Habitat Conservation Plan.
An Administrative Draft Feasibility Study (FS) was completed in December 2017 and
delivered to City Staff and the City Council subcommittee for review and input prior to
being released to the public. On December 22, 2017, the Draft FS was placed on the
City’s website for community review (Attachment A), and a listserv message was issued
announcing its availability and City Council’s review of the document at tonight’s
meeting.
The Draft Feasibility Study document follows the following format:
Section 1: Introduction, which includes project background, history, project purpose,
projection area definition, and community involvement.
Section 2: Summary of the relevant previous work.
Section 3: Physical characteristics of the project area, which includes topography,
watershed hydrology, soils, geology, ground water, and landslide
characteristics.
Section 4: Infrastructure concerns and appropriate environmental requirements,
remedial action objectives, broad classes of available technologies for
response actions to control movement of the Portuguese Bend Landslide
Complex (PBLC), detail discussion and analysis (presenting pros and cons)
and finally preferred alternatives including an estimate of the cost for
implementation of the selected remedy.
The Draft FS identifies the following general actions that could potentially remediate the
landslide:
• Stormwater control
• Subsurface dewatering
• Engineered slope stabilization measures
• Eliminate septic system discharge
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To achieve these actions, the Draft FS considered common technologies available in the
industry to remediate the PB Landslide, including the following (a detailed description can
be found on Page 52 of the Draft FS):
• Repair Existing Corrugated Piping Systems
• Install Concrete Swales
• Install Linear and Channel Systems
• Seal Surface Fractures
• Groundwater Extraction Pits
• Groundwater Extraction Wells
• Directional Subsurface Drains
• Buttressing
• Mechanically Stabilized Earth Wall
• Drilled Piers
• Centralized Sewer System
• Surf erosion/off-shore breakwater
The above list of technologies were screened and narrowed based on known
conditions. The following technology alternatives were retained for more detailed
evaluation:
• Concrete Channels
• Flexible Liner System and Components
• Seal Surface Fractures
• Groundwater Extraction Wells
• Directional Subsurface Drains
• Centralized Sewer System
The evaluation criteria used to analyze the above alternative technologies was based on
the following:
• Overall protection of human health and environment
• Compliance with applicable environmental rules and regulations
• Long-term Effectiveness and Permanence
• Short-term Effectiveness
• Implement ability
• Cost
• State and Community Acceptance.
Based on the evaluation and discussions presented in the body of the study, the following
approach was selected as the Consultant’s preferred alternative remedy. The proposed
remedies that comprise the preferred alternative were identified based on the assumption
of the effects/impacts of a “100 year storm event”:
• Seal surface fractures.
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• Directional subsurface drains.
• Surface drainage control using a flexible liner system and components.
• Ground water extraction wells.
• Centralized sewer system.
Staff seeks the City Council’s input on the Consultant’s recommended landslide
remediation measures prior to finalization of the Draft Feasibility Study for adoption.
Consistency with the Natural Communities Conservation Plan/Habitat
Conservation Plan
On October 2, 2017, the City Council held a workshop to receive a status report on the
Natural Communities Conservation Plan (NCCP) and Habitat Conservation Plan (HCP).
That evening, the City Council was informed that, because of the relatively high
concentration of federally protected coastal sage scrub habitat in the City, and the
growing intensity of development pressures on these areas combined with the ability to
streamline the entitlement process for City projects (i.e., storm drain, road repairs, and
landslide remediation projects), in 1996, the City entered into a Planning Agreement to
develop an NCCP/HCP proposal that will encompass the entire City with the California
Department of Fish and Wildlife (CDFW) and the U.S. Fish and Wildlife Service
(USFWS), referred to as the “Wildlife Agencies.” It was also reported that an important
objective of the NCCP/HCP is for the City to obtain State and Federal Permits from the
Wildlife Agencies for Covered Activities, which include City and private projects.
At that workshop, it was reported that over the past year, the City Council
Subcommittee has been exploring methods to remediate the landslide at Portuguese
Bend, and that the feasibility study was being prepared within the parameters of the
NCCP/HCP. Staff specifically reported that Section 5 of the NCCP/HCP (Attachment D)
identifies covered activities that are permitted to occur in the City, particularly landslide
remediation projects, as part of the City’s “take” permit for any potential loss of Coastal
Sage Scrub (CSS) and Grasslands, as called out in Table 5.1 as follows:
City Project Name
Total Habitat Loss
(Acres)
Habitat Loss In
Preserve (Acres)
CSS Grassland CSS Grassland
1. Altamira Canyon Drainage Project 2.5 3 0 0
2. Dewatering Wells 2.5 2.5 2.5 2.5
3. Landslide Abatement Measures 5.0 15.0 3.3 9.9
4. Misc. Drainage Repair in Landslide Areas 10.0 15.0 6.6 9.9
5. PVDE Drainage Improvement Project 5.0 15.0 0 0
6. Misc. Drainage Improvements 20.0 60.0 6.6 20.0
7. Abalone Cove Beach Project 1.0 2.0 1.0 2.0
8. *RPV Trails Plan Implementation 4.0 10.0 2.0 5.0
9. Lower San Ramon Canyon Repair 5.0 15.0 2.5 7.5
10. Lower Point Vicente 1.5 11.2 0 0
11. Palos Verdes Drive South Road Repair 5.0 15.0 5.0 15.0
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City Project Name
Total Habitat Loss
(Acres)
Habitat Loss In
Preserve (Acres)
CSS Grassland CSS Grassland
12. Upper Pt. Vicente 2.0 22.0 1.0 11.0
13. Preserve Fuel Modification 12.0 18 12.0 18
14. Utility Maintenance and Repair 10.0 20.0 5.0 10.0
15. Unimproved City Park Projects 10.0 20.0 0 0
16. Malaga Canyon Drainage Improvements 5.0 15.0 5.0 15.0
17. Other Miscellaneous City projects 20.0 60.0 10.0 30.0
**Total Acreage of Habitat Loss 120.5 318.7 62.5 155.8
Based on the above table, and the breadth and scope of the Draft FS, Staff has
determined that the proposed remediation technologies described in the previous
section of this Staff report adhere to the following Covered Activities that can occur in
the City pursuant to the current Draft NCCP/HCP (prepared in collaboration between
City Staff, Palos Verdes Peninsula Land Conservancy Staff, and the Wildlife Agencies)
that was presented to the Council in October 2017 (excerpt from the NCCP/HCP):
• 5.2.2 Dewatering Wells
The installation of dewatering wells by the City in areas affected by the Portuguese
Bend and Abalone Cove landslides has proven to be an effective method of slowing
down landslide movement by removing groundwater from the slide plane. It is
anticipated that new wells will be installed by the City in the future in or near areas of
existing CSS habitat and grassland throughout landslide areas. It is estimated a
maximum of 2.5 acres of CSS and 2.5 acres of non-native grassland will be impacted in
the Preserve. A point location for one gnatcatcher occurs in the project vicinity.
• 5.2.3 Landslide Abatement Measures
When and where required, landslide abatement activities within the Preserve and
throughout the City are sometimes necessary by the City or other public agencies to
safeguard existing roads, trails and drainage systems. Such activities include, but are
not limited to (emphasis added), the installation and maintenance of groundwater
monitoring wells and GPS stations (with associated equipment such as pumps,
electrical connections, drainage pipes and access pathways) for the purpose of
monitoring landslide movement, the filling of fissures, the re-contouring of slide debris,
the creation and maintenance of emergency access roads, and geologic investigations
involving trenching or boring performed mechanically or by hand (with allowance for
access of any necessary mechanical equipment). Where practicable, areas of
temporary CSS disturbance will be promptly re-vegetated with CSS habitat after
completion of abatement activities (see Section 6.0 of the Plan for details about the
restoration plan). It is estimated that such landslide abatement measures will result in
the combined loss of a maximum of 5 acres of CSS habitat and 15 acres of non-native
grassland. It is estimated that two-thirds of the impacts will occur within the Preserve.
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Point locations for two gnatcatchers and one island green dudleya occur in areas
potentially subject to landslides.
• 5.2.4 Miscellaneous Drainage Repair in Landslide Areas
The repair of existing drainage systems becomes necessary by the City in landslide
areas because of excessively heavy rainfall or damage by landslide movement. It is
anticipated that there will be a need to repair such drains on an as-needed basis. It is
estimated that such activity will result in the combined loss of a maximum of 10 acres of
CSS habitat and 15 acres of non-native grassland. It is estimated that two-thirds of the
impacts will occur within the Preserve. Point locations for two gnatcatchers, two
aphanisma, one south coast saltscale, and one island green dudleya occur in areas
potentially subject to landslides.
• 5.2.14 Utility Maintenance and Repair
The installation, maintenance and repair of utilities and related infrastructure facilities by
the City, other public agencies and/or utility companies, such as sewers, water, cable,
telephone, gas, power, and storm drains (emphasis added) will occur throughout the
City on an as-needed basis. Installation of new commercial antenna towers is not
allowed in the Preserve. The installation, maintenance, and repair of these activities are
anticipated to permanently impact up to 10 acres of CSS and 20 acres of non-native
grassland throughout the life of the permits. It is estimated that one-half of the impacts
will occur within the Preserve.
To summarize, the Covered Activities described above include, but are not limited to,
the installation and maintenance of groundwater monitoring wells and GPS stations for
the purpose of monitoring landslide movement, the filling of fissures, the re-contouring
of slide debris, the creation and maintenance of emergency access roads, and geologic
investigations involving trenching or boring performed mechanically or by hand. Where
practicable, areas of temporary CSS disturbance will be promptly re-vegetated with
CSS habitat after completion of abatement activities. The NCCP/HCP provides details
for the provision of a maximum of 27.5 acres of CSS habitat and 52.5 acres of
grassland for activities and projects such as dewatering well, landslide abatement
measures, drainage repair, and utility maintenance and repair in landslide areas
(combined Preserve and non-Preserve properties), as detailed in the table below.
Available Habitat Loss for NCCP/HCP Covered Activities
Covered Activities
Total Habitat Loss (Acres) Total Habitat Loss
In Preserve (Acres)
Coastal
Sage Scrub Grassland
Coastal
Sage Scrub Grassland
2. Dewatering Wells 2.5 2.5 2.5 2.5
3. Landslide Abatement
Measures 5.0 15.0 3.3 9.9
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Available Habitat Loss for NCCP/HCP Covered Activities
Covered Activities
Total Habitat Loss (Acres) Total Habitat Loss
In Preserve (Acres)
Coastal
Sage Scrub Grassland
Coastal
Sage Scrub Grassland
4. Misc. Drainage Repair in
Landslide Areas 10.0 15.0 6.6 9.9
14. Utility Maintenance and
Repair 10.0 20.0 5.0 10.0
Total 27.5 52.5 17.4 32.3
To ensure that the remediation technologies proposed in the Draft FS adhere to the
habitat loss allowed for Covered Activities pursuant to the future permit that will be
issued to the City by the Wildlife Agencies after the NCCP/HCP is adopted by the City
Council, DBS&A prepared a revised conceptual plan delineating the proposed work
area over the surveyed Vegetation and Species maps included in the NCCP/HCP
(Attachment B). Expecting the surface drain work area within the City (the covered area
of the NCCP/HCP) that would divert water runoff to the ocean based on a “100-year
storm event” is approximately 65-feet in width, the following loss to CSS and Grassland
is expected to occur (unrestricted area is in other words disturbed area, such as roads,
development, etc.):
Proposed Project Work Areas
Work Description
Total Habitat Loss (Acres) In Preserve (Acres)
Coastal
Sage Scrub Grassland Unrestricted
Coastal
Sage Scrub Grassland Unrestricted
Upper Portuguese Channel 4.0 0 1.0 4.0 0 1.0
Ishibashi Channel 5.2 0 0 4.0 1.2 0
Paintbrush Channel 2.5 0.1 0.3 2.3 0.1 0.3
Lower Portuguese Channel 0.2 2.5 1.3 0.2 1.0 0.0
Central Channel 0.5 1.3 0.3 0.5 1.3 0.3
East Channel 0.2 2.0 0.5 0.2 0.4 0.2
Ocean Discharge 0 1.1 0 0 0 0
Surface Fracture Infilling 0.2 0.2 0 0.2 0.2 0
Wells Permanent Work
Area 0.1 0.1 0.2 0.01 0.01 0.01
Wells Temporary Work
Area 0.3 1.1 2.0 0.1 0.1 0.1
Well Access Roads 0.3 1.1 0.2 0.1 0.3 0.1
Horizontal Drains
Permanent Work Area 0.02 0.04 0 0.01 0.02 0
Horizontal Drains
Temporary Work Area 0.2 0.4 0 0.1 0.2 0
Sewer Mains (In roadways) 0 0 0 0 0 0
Total 13.6 10.0 5.7 11.6 4.8 2.0
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With project implementation within the Palos Verdes Nature Preserve, there will be
approximately 5.8 acres of unused CSS loss and 27.5 acres of unused Grassland loss
available for future projects. As an added measure to ensure the City is able to conduct
projects in the future that may not have been captured in the Covered Activities
described in Table 5.1 of the NCCP/HCP, the following miscellaneous covered activity
is included in the current NCCP/HCP that provides the City with additional CSS and
Grassland loss, including within the Preserve:
• 5.2.17 Other Miscellaneous City Projects
It is foreseeable that during the life of this NCCP/HCP, the City will undertake a City
project similar in character and impacts to those listed in Table 5-1 that is not
specifically listed here as a Covered Project/Activity. Such projects shall be considered
Covered Projects provided the total loss of CSS habitat and non-native grassland for
said Miscellaneous City Projects does not exceed 20 acres of CSS habitat and 60 acres
of non-native grassland as identified in Table 5-1. It is estimated that one-half of the
impacts will occur within the Preserve.
Soon after the October 2, 2017, NCCP workshop, City Staff, the PVPLC Staff, the
Wildlife Agencies, and DBS&A Staff met to discuss the NCCP/HCP in relation to the
Draft FS, and that some preliminary draft editing occurred to Section 5 to reflect the
work described in the Draft FS. However, based on the above, Staff is of the opinion
that the work proposed in the Draft FS adheres to the parameters of the current
NCCP/HCP, and that no edits to the document are needed. The Covered Activities
described in the NCCP/HCP are intentionally written broadly to allow the City maximum
flexibility in conducting projects throughout the City, including landslide abatement
measures, originally envisioned by the City Council in 1996 when they signed on to
develop a NCCP/HCP.
ADDITIONAL INFORMATION:
Next Steps
If the Council adopts the Portuguese Bend Landslide Feasibility Study, the following
steps will need to occur before breaking ground (not in any particular order):
• Adoption of the NCCP/HCP and Permit issuance by the Wildlife Agencies
• Pre-Pilot Test Investigations and Pilot Testing/Reporting
• Preparation of Engineering Plans
• Identifying and Securing Funding Sources
• Hiring a Construction Contractor
• Obtaining Permits from Army Corps of Engineers for work within a blue-line
stream
• City Council Adoption of an Environmental Document pursuant to the California
Environmental Quality Act
• Obtaining a Coastal Development Permit from the Coastal Commission
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• On-going Public Workshops
Public Notification
On December 22, 2017, a listserv was issued to “Breaking News” subscribers and a
message posted on the City’s Facebook and Nextdoor pages announcing the
availability of the Draft FS and tonight’s meeting.
Public Comments
Since the release of the Draft FS on December 22, 2017, the City has received 1 public
comment (Attachment E).
ALTERNATIVES:
In addition to the Staff recommendations, the following alternative actions are available
for the City Council’s consideration:
1. Identify any issues of concern with the Draft FS, and provide City Staff and
DBS&A with direction in modifying the document.
2. Take no action
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PRELIMINARY DRAFT SUBJECT TO CHANGE
Figure 1
FEASIBILITY STUDY UPDATEPORTUGUESE BEND LANDSLIDE COMPLEXRevised Feasibility Study Work Areas Conceptual DesignDaniel B. Stephens & Associates, Inc.01/05/2018 DB 17.1200
0 1000 2000 Feet
Explanation
PV Nature Preserve
Area of greatest land movement
Rolling Hills
Current drainage
Contour interval
Streets
Proposed Work Areas
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Proposed Extraction Well
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Surface fracture infilling area
Channel work area (65' width)
Surveyed Vegetation
Unrestricted Land
Restricted Land - CSS
Restricted Land - Grassland
Surveyed Species Name
Aphanisma
Astragalus Trichopodus
Bright Green Dudleya
California Gnatcatcher
Catalina Boxthorn
Catalina Crabapple Bush
Catalina Mariposa Lily
Coastal Cactus Wren
El Segundo Blue Butterfly
Eriogonum Parvifolium
Lotus Scoparius
Palos Verdes Blue Butterfly
South Coast Saltscale
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LandFlow Subcommittee Notes
July 6, 2017
Questions/Requests
1.How much has been spent over the last 40 years?
a.Answer-Close to 45 million
2.Study on cost of bridge? Mo
3.Hydrology/Geotech Engineers
4.How to prioritize areas? Are engineers going to do that? Yes, “bang for buck”
5.Are we going to see as developed? Yes
What major actions do you propose about the land flow and the interior?
1.Low spots minimized
2.Natural Springs
3.Regular groundwater
4.Water into fissures comes also from drainage channels-How to do away with the
fissures?
5.More current study on ground water coming from up above (VOTES=6) related to
#28
6.Current geological study on current level of saturation
7.Number gallons of water from septic tanks ______ lines (than water imported for
use)
8.Land movement comes after rains; recognize this is biggest source of land
movement
9.4 ft./3ft drainage pipes: Go back to study that determined to put those in and then
decide not to maintain them (~1984)-related to #31 (VOTES=8)
10.Consider maintenance costs with all solutions (VOTES=3)
11.Like board survey on where water is in soil; how much water is absorbed into the
clay; how much is free water? (VOTES=9)
12.Infrastructural project that captures and treats our sources of water for re-use (not
chucking it all). Along with lines of city’s capturing storm water (VOTES=2)
13.Organized analysis what all of this is going to cost and potential maintenance-Macro
cost (VOTES=1)
14.Insight into debt service
15.How much income could we possibly capture from water re-use?
16.Project life cycle cost and potential revenue (VOTES=2)
17.Is getting rid of free water good enough? (Science on this?) That clay still provides
mechanism for slide to move? (VOTES=1)
18.Are we looking at clay as plastic medium-slick surface factor of clay?
19.Is Douglas 2013 study still valid?
20.Could we get a short reading list?
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5.0 COVERED PROJECTS AND ACTIVITIES
5.1 Summary of Covered Projects and Activities
This NCCP/HCP assumes incidental take coverage for 17 Covered City Projects and Activities (see Section
5.2), five private projects (see Section 5.3), and other specific activities in the Preserve (see Section 5.4),
provided that the projects and activities are consistent with the applicable Habitat Impact Avoidance and
Minimization Measures described in Section 5.5 of the NCCP/HCP. “Projects” are well-defined actions
that occur once in a discrete location whereas “Activities” are actions/operations that occur repeatedly in
one location or throughout the Plan Area. The City’s dedication and management to the Preserve of 1,123
acres, including the 499.9 acres of City Mitigation Lands, the management of 258.7 acres of Previous
Mitigation Lands, and 20.7 acres of PVPLC lands, is intended to provide the necessary mitigation for CSS
and grassland for Covered City and Miscellaneous Private Projects and Activities (both outside and inside
the Preserve). Any potential impacts to properties within the Plan Area that were previously acquired with
nontraditional section 6 HCP Land Acquisition grant funding (61.5 acres in Malaga Canyon) and funding
provided the State will be subject to review and approval by the Wildlife Agencies to confirm consistency
with the section 6 grant program and requirements associated with other State funding. All Covered
Activities will be reviewed by the City to ensure their consistency with the NCCP/HCP. As they are
proposed, the projects will be forwarded to and may be reviewed by the Wildlife Agencies during the
applicable CEQA process (or other process) for consistency with this NCCP/HCP.
The Covered City Projects/Activities are proposed to occur inside and outside of the Preserve and are
anticipated to impact a maximum of 318.7 acres of non-native grassland and 120.5 acres of CSS. Of these
total impacts, it is estimated that 62.5 acres of the impacted CSS (52%) and 155.8 acres of the impacted
non-native grassland (49%) will occur within the Preserve. Included in the CSS loss are losses associated
with southern cactus scrub, saltbush scrub, and coastal bluff scrub which are expected to be minimal. No
more than 5 acres of southern cactus scrub, 2 acres of coastal bluff scrub, and 2 acres of saltbush scrub
could be lost within the Preserve associated with Covered City Projects/Activities. The City will mitigate
these impacts by dedicating land to the City lands to the Preserve and providing restoration and management
funding for the Preserve (see Section 8.0). Of the 737 acres of CSS and associated vegetation communities
within the Preserve, a maximum of 62.5 acres (<9%) could be impacted by Covered City
Projects/Activities, leaving a minimum of 674.5 acres (92%) of CSS in the Preserve to be perpetually
conserved. Of the 470.9 acres of grassland within the Preserve, a maximum of 155.8 acres (33%) could be
impacted by Covered City Projects/Activities, leaving a minimum of 315.1 acres. Through Plan
implementation non-native grassland within the Preserve may be restored to native habitat. Impacts to
specific vegetation communities within and outside of the Preserve are described in individual project
descriptions (Section 5.2).
The Covered Private Projects are proposed to occur outside of the Preserve and are anticipated to impact a
maximum of 262.8 acres of grassland and 99.5 acres of CSS. These impacts as summarized below and will
be mitigated by each project proponent. Impacts to specific vegetation communities are described in
individual project descriptions (Section 5.3). The total loss of habitat associated with Covered Project and
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Activities are quantified above. The effects of the habitat loss to the Covered Species are described in the
conservation analysis in Appendix B of the Plan.
Within the Coastal Zone, permissible impacts and mitigation to Environmentally Sensitive Habitat Areas
(ESHA), as defined in Appendix F, will not only be consistent with the NCCP/HCP, but will also be
consistent with the City’s most current LCP. Furthermore, any impacts to habitat or ESHA’s located in the
Coastal Zone will be mitigated within the Coastal Zone.
The NCCP/HCP area will be subject to CWA Sections 401 and 404, and California Fish and Game Code
Section 1600 et seq. permit requirements if they are included within areas proposed for development.
5.2 Covered City Projects and Activities
The following proposed Covered City Projects are addressed by this NCCP/HCP (see summary on Table
5-1 and Figure 5-2) and will be encumbered by conservation easements which are to be recorded on City-
owned properties within the Preserve pursuant to Section 4.2 of this Plan. All mitigation for Covered City
Projects/Activities will occur within the Preserve.
5.2.1 Altamira Canyon Drainage Project
The City has identified the need for a project within the portion of Altamira Canyon that traverses the
Portuguese Bend landslide area to address drainage and erosion and to prevent water from percolating into
the landslide plane. The removal of the Canyon’s existing vegetation will result in the loss of 2.5 acres of
CSS habitat and 3 acres of non-native grassland. Point locations for one gnatcatcher and one PVB hostplant
occur in the project vicinity. Although this project is not being proposed at this time, it is likely that the
project will be actively pursued during the life of the NCCP/HCP.
5.2.2 Dewatering Wells
The installation of dewatering wells by the City in areas affected by the Portuguese Bend and Abalone Cove
landslides has proven to be an effective method of slowing down landslide movement by removing
groundwater from the slide plane. It is anticipated that new wells will be installed by the City in the future
in or near areas of existing CSS habitat and grassland throughout landslide areas. It is estimated a maximum
of 2.5 acres of CSS and 2.5 acres of non-native grassland will be impacted in the Preserve. A point location
for one gnatcatcher occurs in the project vicinity.
5.2.3 Landslide Abatement Measures
When and where required, landslide abatement activities within the Preserve and throughout the City are
sometimes necessary by the City or other public agencies to safeguard existing roads, trails and drainage
systems. Such activities include, but are not limited to, the installation and maintenance of groundwater
monitoring wells and GPS stations (with associated equipment such as pumps, electrical connections,
drainage pipes and access pathways) for the purpose of monitoring landslide movement, the filling of
fissures, the re-contouring of slide debris, the creation and maintenance of emergency access roads, and
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geologic investigations involving trenching or boring performed mechanically or by hand (with allowance
for access of any necessary mechanical equipment). Where practicable, areas of temporary CSS disturbance
will be promptly re-vegetated with CSS habitat after completion of abatement activities (see Section 6.0 of
the Plan for details about the restoration plan). It is estimated that such landslide abatement measures will
result in the combined loss of a maximum of 5 acres of CSS habitat and 15 acres of non-native grassland.
It is estimated that two-thirds of the impacts will occur within the Preserve. Point locations for two
gnatcatchers and one island green dudleya occur in areas potentially subject to landslides.
15-1. Brush Management in Preserve for Fire Prevention Purposes
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25-2. Locations of City Projects Covered by the NCCP/HCP
5.2.4 Miscellaneous Drainage Repair in Landslide Areas
The repair of existing drainage systems becomes necessary by the City in landslide areas because of
excessively heavy rainfall or damage by landslide movement. It is anticipated that there will be a need to
repair such drains on an as-needed basis. It is estimated that such activity will result in the combined loss
of a maximum of 10 acres of CSS habitat and 15 acres of non-native grassland. It is estimated that two-
thirds of the impacts will occur within the Preserve. Point locations for two gnatcatchers, two aphanisma,
one south coast saltscale, and one island green dudleya occur in areas potentially subject to landslides.
5.2.5 Palos Verdes Drive East Drainage Improvement Project
Based on a comprehensive drainage study, the City has identified numerous drainage system deficiencies
in the eastern portion of the City along Palos Verdes Drive East (PVDE). To address these drainage
deficiencies, the City proposes to carry out several drainage improvement projects over an extended period
of time. Although it is anticipated that most of the projects will occur within the existing improved street
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right-of-way, some projects may necessitate work in the adjoining canyon areas. It is estimated that such
activity will result in the combined loss of a maximum of 5 acres of CSS habitat and 15 acres of non-native
grassland outside the Preserve. Point locations for Covered species are not currently known from the
proposed project area.
5.2.6 Miscellaneous Drainage Improvements
The City anticipates that there will be the need to perform regular maintenance, repairs and upgrades on
drainage systems in the City not located within the landslide areas or the Palos Verdes Drive East drainage
project area. It is anticipated that the repair and improvement of these drainage systems will be necessary
from time to time due to unexpected storm damage or due to the old age of the drainage systems. It is also
anticipated that some of the projects may necessitate the creation and/or maintenance of retention basins,
debris basins, and access roads. It is estimated that such activity could result in the combined loss of a
maximum of 20 acres of CSS habitat and 60 acres of grassland in the Plan area. Of this total, it is estimated
that 6.6 acres of CSS (33%) and 20 acres of grassland (33%) impacts will occur in the Preserve. Point
locations for three gnatcatchers, two cactus wrens, two PVB hostplants, one ESB hostplant, one aphanisma,
one island green dudleya and one woolly seablite occur in the vicinity of the proposed project(s).
5.2.7 Abalone Cove Beach Project
The City has identified a need to improve public access and beach amenities at the existing Abalone Cove
beach site. The project may involve the construction of a restroom/storage area, a gate house, parking lot,
and shade structures, as well as improving the access road that leads from Palos Verdes Drive South to the
beach and foot trails in the area. The grading associated with the proposed project may cause the loss of 1
acre of CSS habitat and 2 acres of non-native grassland within the Preserve. Any CSS re-vegetation shall
be performed on site within the coastal zone of the Preserve. A point location for one island green dudleya
occurs in the vicinity of the proposed project. Although this project is not being proposed at this time, it is
possible that the project or a similar variation will be actively pursued during the life of this NCCP/HCP.
5.2.8 Rancho Palos Verdes Trails Plan Implementation
The City’s Trails Network Plan addresses existing and proposed trails outside and within the Preserve. The
portion of the Trails Network Plan that addresses trails within the Preserve is a part of the Public Use
Management Plan (PUMP), which is a Covered City Project described further in Sections 5.4.2 and 9.2.1
of this Plan. It is anticipated that implementation of the City’s Trails Network Plan, which includes the
Preserve Trails Plan component (see Sections 5.4.2 and 9.2.1.1), will result in the loss of some CSS and
grassland habitat. Although the establishment of new trails through CSS habitat will be avoided where
possible, it is anticipated that some trail maintenance, erosion repair, and re-routing for public safety reasons
may occur within habitat areas. Although it is anticipated that trail widening could occur as a result of trail
use over time, trails will be monitored for signs of widening, and managed to remedy the degradation (see
Section 9.2.2.2 of the Plan). It is estimated that such activities will result in the combined loss of a maximum
of 4 acres of CSS habitat and 10 acres of grassland. It is estimated that one-half of these impacts will occur
within the Preserve (2 acres of CSS habitat and 5 acres of grassland). Point locations for two PVB
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hostplants, one ESB hostplant, one island green dudleya, and one woolly seablite occur in the vicinity of
the Preserve Trails Plan.
5.2.9 Lower San Ramon Canyon Repair
It is anticipated that the City will undertake a major stormwater project in the Lower San Ramon Canyon
to reverse the effects of erosion on the streambed in an attempt to reduce the active Tarapaca landslide from
blocking water flow. Geologic studies have identified a landslide in the canyon that has the potential to
create blockage of the stream flow. Blockage of the stream flow could cause water to percolate into the
adjacent South Shores landslide. The project will reduce the likelihood of reactivating the South Shores
landslide, which could result in the loss of the Switchbacks on Palos Verdes Drive East. It is estimated that
the project will result in the loss of a maximum of 5 acres of CSS and 15 acres of grassland. It is estimated
that one-half of the impacts will occur in the Preserve. One point location for one gnatcatcher occurs in the
project vicinity.
5.2.10 Lower Point Vicente
Pursuant to the City’s approved Vision Plan, the City may develop a public recreational/educational project
to augment the existing Point Vicente Interpretive Center located on a parcel of City-owned land referred
to as Lower Point Vicente. The property is located between the Point Vicente Lighthouse property owned
by the Coast Guard and the Oceanfront Estates residential development project. It is anticipated that
development of the site may result in a maximum loss of 1.5 acres of CSS and 11.2 acres of non-native
grassland outside of the Preserve. One point location for one ESB hostplant occurs in the vicinity of the
proposed project.
5.2.11 Palos Verdes Drive South Road Repair
The City anticipates that due to continual landslide movement in the Portuguese Bend landslide area, there
will be a need to perform repair work on the portion of Palos Verdes Drive South that traverses the landslide,
including but not limited to relocating the roadway if necessary. It is anticipated that such road repair
activity may result in a maximum of 5 acres of CSS habitat loss and 15 acres of non-native grassland loss
within the Preserve. One point location for one PVB hostplant occurs in the vicinity of the proposed project.
5.2.12 Upper Point Vicente
As part of the City’s approved Vision Plan, the City is considering development of a
civic/cultural/community center at Upper Point Vicente Park. The project may result in a loss of 2 acres of
CSS and 22 acres of non-native grassland. It is estimated that one-half of the impacts will occur within the
Preserve. Point locations for one gnatcatcher and one cactus wren occur in the vicinity of the proposed
project.
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5.2.13 Preserve Fuel Modification
The City and PVPLC are required to perform annual fuel modification for fire prevention purposes within
the Preserve by the Weed Abatement Division of the Los Angeles County Department of Agricultural
Commissioner. The location and amount of fuel modification throughout the Preserve has been determined
by the Los Angeles Weed Abatement Division in conjunction with the Los Angeles County Fire Department
(see Figure 5-1) and is based on factors such as proximity of structures, steepness of slope, and fuel load.
The methods for carrying out the required fuel modification are described in Section 9.2.2 of the Plan. The
required City fuel modification is anticipated to result in a loss of 12 acres of CSS and 18 acres of non-
native grassland in the Preserve. Changes to fuel modification that would result in greater impacts than
depicted in Figure 5-1 and Table 5-1 would require additional review by the Wildlife Agencies and PVPLC,
potentially including amending the Plan pursuant to Section 6.8 of the Plan.
5.2.14 Utility Maintenance and Repair
The installation, maintenance and repair of utilities and related infrastructure facilities by the City, other
public agencies and/or utility companies, such as sewers, water, cable, telephone, gas, power, and storm
drains will occur throughout the City on an as-needed basis. Installation of new commercial antenna towers
is not allowed in the Preserve. The installation, maintenance, and repair of these activities are anticipated
to permanently impact up to 10 acres of CSS and 20 acres of non-native grassland throughout the life of
the permits. It is estimated that one-half of the impacts will occur within the Preserve.
5.2.15 Unimproved City Park Projects
In addition to its developed parks, the City has a number of unimproved park sites that may be improved in
the future with recreational amenities. These unimproved parks sites include, but are not limited to, 17.5-
acre Grandview Park, 18.2-acre Lower Hesse Park, 4.7-acre Vanderlip Park, and 1-acre Martingale Park.
It is anticipated that development of these specific park facilities and any other unimproved City park
facilities will result in loss of a maximum of 10 acres of CSS habitat and 20 acres of non-native grassland
outside of the Preserve.
5.2.16 Malaga Canyon Drainage Improvements
The City anticipates that there will be the need to perform regular maintenance, repairs, and upgrades on
the drainage system within the City-owned Malaga Canyon open space. It is anticipated that the repair and
improvement of these drainage systems will be necessary from time to time due to unexpected storm
damage or due to the old age of the drainage systems. It is also anticipated that some of the projects may
necessitate the creation and/or maintenance of retention basins, detention basins, debris basins, and access
roads. It is estimated that such activity could result in the combined loss of a maximum of 5 acres of CSS
habitat and 15 acres of non-native grassland within the Preserve. Any potential impacts will be offset to
ensure that the biological values of the properties are maintained consistent with the section 6 grant funding
used to acquire the property and will be subject to review and approval by the Wildlife Agencies.
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5.2.17 Other Miscellaneous City Projects
It is foreseeable that during the life of this NCCP/HCP the City will undertake a City project similar in
character and impacts to those listed in Table 5-1 that is not specifically listed here as a Covered
Project/Activity. Such projects shall be considered Covered Projects provided the total loss of CSS habitat
and non-native grassland for said Miscellaneous City Projects does not exceed 20 acres of CSS habitat and
60 acres of non-native grassland as identified in Table 5-1. It is estimated that one-half of the impacts will
occur within the Preserve.
15-1. Total Loss of Habitat by Covered City Projects and Activities
City Project Name
Total Habitat Loss
(Acres)
Habitat Loss In
Preserve (Acres)
CSS Grassland CSS Grassland
1. Altamira Canyon Drainage Project 2.5 3 0 0
2. Dewatering Wells 2.5 2.5 2.5 2.5
3. Landslide Abatement Measures 5.0 15.0 3.3 9.9
4. Misc. Drainage Repair in Landslide Areas 10.0 15.0 6.6 9.9
5. PVDE Drainage Improvement Project 5.0 15.0 0 0
6. Misc. Drainage Improvements 20.0 60.0 6.6 20.0
7. Abalone Cove Beach Project 1.0 2.0 1.0 2.0
8. *RPV Trails Plan Implementation 4.0 10.0 2.0 5.0
9. Lower San Ramon Canyon Repair 5.0 15.0 2.5 7.5
10. Lower Point Vicente 1.5 11.2 0 0
11. Palos Verdes Drive South Road Repair 5.0 15.0 5.0 15.0
12. Upper Pt. Vicente 2.0 22.0 1.0 11.0
13. Preserve Fuel Modification 12.0 18 12.0 18
14. Utility Maintenance and Repair 10.0 20.0 5.0 10.0
15. Unimproved City Park Projects 10.0 20.0 0 0
16. Malaga Canyon Drainage Improvements 5.0 15.0 5.0 15.0
17. Other Miscellaneous City projects 20.0 60.0 10.0 30.0
**Total Acreage of Habitat Loss 120.5 318.7 62.5 155.8
*Part of the PUMP, a Covered City Project (see Section 9.2 of this Plan)
**Total habitat loss (CSS and Grassland) is 439.2 acres, of which 218.3 acres (50%) would occur in the Preserve. Included in the
CSS loss are losses associated with southern cactus scrub, saltbush scrub, and coastal bluff scrub which are expected to be minimal.
No more than 5 acres of southern cactus scrub, 2 acres of coastal bluff scrub, and 2 acres of saltbush scrub could be lost within the
Preserve associated with Covered City Projects and Activities.
5.3 Covered Private Projects and Activities
The following proposed Private Projects and Activities are covered (Covered Private Projects and
Activities) by this NCCP/HCP (see Table 5-2 and Figure 5-4 below).
5.3.1 Lower Filiorum Development
If any type of development project is approved on the 94.2-acre Lower Filorum property, also known as
the Point View property, the owner will be required as a condition of approval to dedicate to the Preserve
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a minimum of 40 acres of the 94.22-acre property, including a minimum 300-foot-wide functional wildlife
corridor on the southern edge of the property connecting to the Abalone Cove portion of the Preserve, as
depicted in Figure 5-3, as mitigation for impacts to biological resources. Any required fuel modification for
the proposed project will not encroach into the area dedicated to the Preserve, including the 300-foot
wildlife corridor. The City will work with the landowner to prepare a development agreement which will
include a funding program for management and monitoring the lands to be dedicated to the Preserve.
The intent of the 40-acre dedication and 300-foot-wide minimum wildlife corridor required for this project
is to maintain a viable wildlife corridor through the Preserve after the proposed project is approved and
constructed. Based on a biology report prepared by NRC in 2003, the Point View property is comprised of
70 acres of non-native grassland, 2.5 acres of CSS, 9.4 acres of disturbed CSS, 6.9 acres of exotic woodland,
and 5.2 acres of disturbed vegetation. The minimum of 40 acres of dedicated Preserve shall include 1.5
acres to be provided as mitigation for previous brush clearing activities and 38.5 acres of mitigation for
CSS and grassland losses resulting from any future development of the 94.22-acre Lower Filiorum parcel.
The inclusion of Lower Filiorum acreage in the Preserve will be a condition of approval for any
development project subsequently approved for the Lower Filiorum property. If no approvals are obtained,
there will be no obligation on the part of present or future property owner to dedicate these lands to the
Preserve. Likewise, identifying these lands for potential inclusion in the Preserve in the text and maps of
this NCCP/HCP does not constitute approval of development on the Lower Filiorum property.
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35-3. Potential Preserve for Lower Filiorum
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45-4. Locations of Private Projects Covered by NCCP/HCP
5.3.2 Portuguese Bend Club Remedial Grading
Because of its proximity to the active Klondike Canyon Landslide, the homeowners association of the gated
residential community known as the Portuguese Bend Club may need to perform remedial grading on its
property to prevent damage to its roads and to residents’ homes. It is anticipated that the remedial grading
activity will take place on property owned by the association, located on the western end of the community,
or on the adjoining City-owned property. It is anticipated that the remedial grading activity will result in a
loss of 3 acres of CSS habitat and 10 acres of grassland. One point location for the cactus wren occurs in
the vicinity of this project. Mitigation for this Covered Private Project is addressed by the City conveying
and managing 1,123 acres to the Preserve. For the Private Projects to be covered under the City’s Plan,
vegetation removal shall be offset by the project applicant paying a Mitigation Fee into the City’s Habitat
Restoration Fund using a 2:1 mitigation ratio for impacted CSS, a 0.5:1mitigation ratio for impacted non-
native grassland, and a 3:1 mitigation ratio for impacted native grassland (as described in Section 2.2.1 of
the Plan) occurring in areas greater than 0.3 acre. This Covered Private Project may mitigate by one of the
following two methods: 1) Dedication of additional acreage to the Preserve that will add to the biological
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function of the Preserve (the approval of the City, PVPLC, and the Wildlife Agencies is required for acreage
to be dedicated to the Preserve) and the property owner must provide management funding for the additional
acreage according to a Property Analysis Record or similar method; or 2) Payment of a Mitigation Fee to
the City’s Habitat Restoration Fund described in section 8.2.1.1 in an amount of $50,000 per acre for the
total mitigation acreage required (e.g., 3 acres of CSS impact = $150,000.00). The Mitigation Fee must be
paid to the City prior to the remedial grading taking place. The PVPLC and the City have determined that
$50,000 (in 2015 dollars) is the cost to restore and maintain 1 acre of native habitat. The $50,000 Mitigation
Fee will be reviewed periodically, no less than every three years, by the City and, if necessary, adjusted to
account for inflation and/or higher than expected restoration and management costs.
5.3.3 Fuel Modification for Private Projects throughout the City
For new private development projects on vacant land in the City, all fuel modification required by the Los
Angeles County Fire Department and/or Los Angeles County Department of Agricultural Commissioner
as a result of such new projects will occur outside of the Preserve unless the City and the Los Angeles
County Fire Department and/or Agricultural Commissioner agree that no other options exist. For existing
private development, the Los Angeles County Fire Department and Los Angeles County Department of
Agricultural Commissioner have reviewed the existing private development that abuts the Preserve and
have determined the amount of brush clearance needed within the Preserve to provide the code-required
fuel modification zone for the protection of existing structures outside the Preserve (see Figure 5-1).
In situations where fuel modification must occur in the Preserve, impacts are already addressed by the City
dedicating 1,402.4 acres to the Preserve. For the Private Projects to be covered under the City’s Plan,
vegetation needed to be cleared for fuel modification shall be offset by the project applicant paying a
Mitigation Fee into the City’s Habitat Restoration Fund using a 2:1 mitigation ratio for impacted CSS, a
0.5:1mitigation ratio for impacted non-native grassland, and a 3:1 mitigation ratio for impacted native
grassland (as described in Section 2.2.1 of the Plan) occurring in areas greater than 0.3 acre. Removal of
cacti and other succulents within any required fuel clearing areas shall be avoided/minimized to preserve
habitat for the coastal cactus wren and other Covered Species. The total Mitigation Fee payment required
is calculated by multiplying the total acreage impacted by the required ratio for each habitat type. The
Mitigation Fee payment shall be provided by the property owner benefiting from the fuel modification by
one of the following two methods: 1) Dedication of additional acreage to the Preserve that will add to the
biological function of the Preserve (the approval of the City, PVPLC, and the Wildlife Agencies is required
for acreage to be dedicated to the Preserve) and the property owner must provide management funding for
the additional acreage according to a Property Analysis Record or similar method; or 2) Payment of a
Mitigation Fee to the City’s Habitat Restoration Fund described in section 8.2.1.1 in an amount of $50,000
per acre for the total mitigation acreage required (e.g., 3 acres of CSS impact = $150,000.00). The
Mitigation Fee must be paid to the City prior to the fuel modification taking place. The PVPLC and the
City have determined that $50,000 (in 2013 dollars) is the cost to restore and maintain 1 acre of native
habitat. The $50,000 Mitigation Fee will be reviewed annually by the City and if necessary adjusted to
account for inflation and/or higher than expected restoration and management costs.
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The anticipated loss from fuel modification resulting from Covered Private Projects/Activities within the
Preserve is not expected to exceed 10 acres of CSS and 20 acres of grassland. Any loss of CSS beyond 10
acres and 20 acres of grassland is not a NCCP/HCP Covered Project/Activity.
5.3.4 Miscellaneous Private Projects Throughout the City Outside of the
Preserve
The City may issue a permit for any Private Project in the City which impacts CSS habitat and is not
specifically identified in this NCCP/HCP as a Covered Activity provided that the project impacts are located
outside of the Preserve and the impacts are mitigated by the project applicant as described in this section.
Impacts to CSS shall be mitigated by the project applicant using a 1:1 mitigation ratio for impacted CSS.
Because fire is a natural component of the CSS vegetation community, under normal circumstances natural
re-growth of habitat is expected, and any land that once had CSS will be considered CSS for the purposes
of this Covered Activity. The mitigation shall be provided by the project applicant by the payment of a
Mitigation Fee to the City’s Habitat Restoration Fund discussed in section 8.2.1.1 in the amount of $50,000
per acre based on the total mitigation acreage required. The Mitigation Fee must be paid to the City prior
to issuance of the grading or building permit, whichever comes first. The PVPLC and the City have
determined that $50,000 (in 2013 dollars) is the amount that is needed to restore and maintain 1 acre of
native habitat. The $50,000 Mitigation Fee will be reviewed annually by the City and, if necessary, adjusted
to account for inflation and/or higher-than-expected restoration and management costs.
There are 23.6 acres of exotic woodland, 22.6 acres of disturbed vegetation and 262.8 acres of grassland
located outside of the Preserve or Neutral Lands that will be impacted by potential development with no
mitigation required by individual property owners under this NCCP/HCP because the loss of such lands
would not affect any of the Covered Species. Furthermore, there are 99.5 acres of CSS habitat outside of
both the Preserve and Neutral Lands which include the 27.7 acres of CSS that would be impacted by the
other four specific private projects discussed in this Section 5.3 of the Plan. This would result in the potential
for a total of 71.8 acres of CSS habitat outside the Preserve and Neutral Lands to be lost as a result of these
miscellaneous private projects throughout the City. Since this CSS and grassland exist outside the Preserve
and Neutral Lands and is not targeted for conservation, this Plan is assumes that all of this habitat could be
lost over the life of this Plan as a result of miscellaneous private projects without affecting preserve design
and/or species persistence.
5.3.5 Plumtree Development
If a development project is approved on the 27-acre Plumtree property and the owner opts to rely on this
NCCP/HCP to mitigate any impacts to biological resources caused by the proposed development project,
all impacts to biological resources addressed under this Plan on the 27-acre Plumtree property will be
considered adequately mitigated by the conveyance of 30 acres of functional and connected habitat on the
Upper Filiorum property (190 total acres) in 2009, as described in Section 4.2.1 of the Plan, which has been
dedicated to the Preserve with the appropriate conservation easement (see Appendix G to this Plan). Any
required fuel modification for a proposed project on the Plumtree parcel will not encroach into the area
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dedicated to the Preserve. Based on a biology report prepared by NRC on August 14, 2007, the 27-acre
Plumtree Parcel contains 19.7 acres of non-native grassland and 2.8 acres of disturbed CSS. In addition,
one pair of gnatcatchers was observed.
The donation of the 30-acre parcel by the property owner and its subsequent dedication to the Preserve as
mitigation for any future upland biological impacts does not constitute nor imply approval of any
subsequent development project on the Plumtree property by the City or determination of consistency with
the NCCP/HCP by the Wildlife Agencies.
25-2. Total Loss of Habitat by Privately Covered Projects and Activities
COVERED PRIVATE PROJECT
HABITAT LOSS (ACRES)
CSS GRASSLAND
1. Lower Filiorum Development 11.9 70.0
2. Portuguese Bend Club Remedial Grading 3.0 10.0
3. Fuel Modification for Private Projects 10.0 20.0
4. Miscellaneous Private Projects throughout the City 71.8 143.1
5. Plumtree Development 2.8 19.7
Total Acreage of Habitat Loss 99.5 262.8
5.4 Other Covered Activities
The following Covered Activities are expected to occur in the Preserve due to short- and long-term
operation and maintenance requirements or emergency situations conducted by the City, other public
agencies, or utility companies seeking Third-Party Participant status. These activities are not expected to
involve the permanent loss of habitat. All of these activities listed below may not occur without first
notifying the City. Any activity not identified below as a Covered Activity may not be initiated in the
Preserve without prior notification to the PVPLC and concurrence from the Wildlife Agencies. The
following Covered Activities shall adhere to the Habitat Impact Avoidance and Minimization Measures for
Covered Activities outlined in Section 5.5 of the Plan as part of all operations and authorizations to precede
work, where applicable:
5.4.1 Operation and Maintenance
• Landslide abatement and monitoring activities that do not result in the loss of Covered Species
and/or habitat. The regular maintenance and repair of existing drainage facilities and existing
access roads within the Preserve that does not result in the loss of Covered Species and/or
habitat.
• The maintenance of existing access roads in the Preserve provided there is no loss of Covered
Species and/or habitat.
• Geologic testing and monitoring for public health and safety reasons, provided there is no loss
of Covered Species and/or habitat.
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• Installation, maintenance, and repair of utilities and related infrastructure(s) that are necessary
to serve the Covered Private Projects identified in Section 5.2 of the Plan provided there is no
loss of Covered Species and/or habitat.
• Maintenance and repair of utilities and related infrastructure(s) provided there is no loss of
Covered Species and/or habitat.
• The maintenance and repair of existing water quality basins, retention basins, detention basins,
and debris basins, provided there is no loss of Covered Species and/or habitat.
• Photography and filming, provided a City permit is obtained, no grading is involved, no new
access road or trails are created, and impacts to Covered Species and/or habitat are avoided.
• City and Los Angeles County law enforcement activities, including vehicular access.
5.4.2 Public Use
Public access to the Preserve is conditionally allowed for passive recreational purposes and to promote
understanding and appreciation of natural resources. Excessive or uncontrolled access; however, can result
in habitat degradation through trampling and erosion (e.g., along trails) and disruption of breeding and other
critical wildlife functions at certain times of the year. In order to balance the public’s passive recreational
needs with the protection of natural resources within the Preserve, a Public Use Master Plan (PUMP) has
been developed jointly by the City, the public, and PVPLC to address public access issues. The PUMP is a
proposed City-Covered Project incorporated into the Plan; therefore, it must be approved by the Wildlife
Agencies as part of the NCCP/HCP before the activities, including the Preserve Trails Plans, will be
allowed. The following public uses and activities are considered conditionally Covered Activities in the
Preserve if they conform to the PUMP:
• Public use and implementation of the Preserve Trails Plan (PTP) contained in the Wildlife
Agency-approved PUMP. Section 9.2.1.1 of this Plan provides the design criteria and
guidelines that will be used for the PTP.
• Closure of existing trails within the Preserve that are not included in the PTP, as approved by
the City Council and Wildlife Agencies.
• Passive recreational activities (e.g., horse riding, hiking, bicycling, wildlife viewing) as
described in the PUMP and approved by the City and Wildlife Agencies.
• Subject to the PUMP, the creation and maintenance of passive overlook or vista areas with
seating benches and trail markers may be located at key vista points near existing trails in the
Preserve, provided no existing habitat will be lost. The location of these overlooks shall be
located to avoid or minimize direct and indirect impacts to biological resources. The location
of these overlooks will be approved by City Council.
• Installation and maintenance of benches, picnic tables, tie rails, portable toilets, and trash cans
within the Preserve and near Preserve boundaries, provided no existing habitat will be lost. The
location of these facilities shall be sited to avoid or minimize direct and indirect impacts to
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habitat and Covered Species. Location of overlooks shall be reviewed for consistency with the
PUMP and this Plan and approved by the City Council prior to initiation of any implementation
work.
• Installation of trailhead signage/kiosks within the Preserve adjacent to existing roads or other
access ways and away from sensitive resource areas. The location of trailhead signage/kiosks
shall be reviewed for consistency with the PUMP and this Plan and approved by the City prior
to initiation of any implementation work.
• Operation and maintenance of the existing archery range in its current location and acreage
(approximately 8 acres) within the Preserve, provided the appropriate City permits are
maintained and the facility is not expanded.
• Operation of the existing agricultural use at Upper Point Vicente of approximately 5 acres in
size provided the appropriate City approval is maintained and all agricultural practices and
improvements remain consistent with this NCCP/HCP. No other agricultural activities are
allowed in the Preserve.
• Night use of the Preserve provided use is limited, controlled, monitored, and managed
consistent with the Palos Verdes Nature Preserve Night Hike Regulations. The City will issue
a permit for night use and any night use of the Preserve shall be consistent with the requirements
of this Plan. A summary of night use in the Preserve will be included in the Annual Report.
5.4.3 Preserve Management
Management of the Preserve in accordance with the provisions described in Sections 8.0 and 9.0 of the Plan
is a Covered Activity. Specific management Covered Activities anticipated to occur in the Preserve include
the following:
• Monitoring of Covered Species
• Vehicular access
• Habitat restoration
• Invasive species control
• Predator control
• Reintroduction of Covered Species
• Photo documentation
• Installation of signage
• Trail maintenance
• Maintenance of fire/fuel buffers
• Field research and studies designed to contribute to the long-term protection of habitats and
species and other basic research of habitats and species included in the Preserve.
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5.5 Habitat Impact Avoidance and Minimization Measures for
Covered Projects and Activities
The City will ensure implementation of the following avoidance and minimization measures as enforceable
conditions in all permits, operations, and authorizations to proceed with the Covered Projects and Activities
listed in Sections 5.2 through 5.4 of this Plan:
1. The City will review proposed plans for Covered Project and Activities within and abutting the
Preserve (e.g., access routes, staging areas) to ensure proposed Covered Activities are consistent
with this NCCP/HCP.
2. The City and its Preserve Habitat Manager (i.e., PVPLC) will ensure that access to the Preserve to
carry out Covered Activities is consistent with the approved Preserve Access Protocol (PAP) that
is required to be created pursuant to Section 6.5.2 of this Plan. When accessing the Preserve, utility
agencies and the City’s Public Works Department must take measures to avoid and minimize, to
the maximum extent possible, environmental damage, including damage to habitat and Covered
Species. Existing access roads in the Preserve should be used wherever practical. Any unavoidable
access routes outside existing roads or construction areas should be clearly marked. Any new roads,
trails, and utility corridors will be located in areas that avoid/minimize impacts to Covered Species,
habitat fragmentation and edge effects. The width of construction corridors and easements will be
minimized.
3. The City and/or responsible private project applicants will be responsible for ensuring that an
Erosion Control Plan is developed and implemented for any Covered Activities in the Preserve or
abutting the Preserve that might result in erosion as determined by the City. Potential erosion
control measures include siltation fencing, straw bales, sand bags, etc.
4. When stockpiling topsoil in the Preserve or on vacant lots abutting the Preserve, it will be placed
only in areas that minimize the damage to habitat. If fill or topsoil is imported into the Preserve,
the fill will be certified weed-free soil.
5. For any new development on vacant lots abutting the Preserve, construction staging areas will be
located at least 15 meters (50 feet) away from the Preserve boundary and natural drainages. No-
fueling zones will extend a minimum distance of 15 meters (50 feet) from all drainages and away
from the Preserve boundary.
6. Construction footprints for Covered Projects and Activities in the Preserve or abutting the Preserve
will be clearly defined with flagging and/or fencing and will be removed upon completion of the
Covered Activities.
7. Cut/fill slopes outside of fuel modification zones within the Preserve will be re-vegetated with
native species, or in the case of fuel modification zones, native plants recommended by Los Angeles
County for fuel modification zones. Impacts to cacti and other succulents within any required fuel
clearing areas shall be avoided/minimized to conserve habitat for the coastal cactus wren and other
Covered Species. Sidecasting of materials during trails, road, and utility construction and
maintenance within the Preserve will be avoided.
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8. Where feasible and appropriate, dust generated by the construction for Covered Activities within
the Preserve or on vacant lots abutting the Preserve will be controlled via watering of earthmoving
areas and non-paved roads and an off-highway speed limit restriction to 20 miles per hour (mph).
9. Any temporary safety or security night lighting for Covered Activities in the Preserve or on vacant
lots abutting the Preserve will be selectively placed, shielded, and directed away from all native
vegetative communities.
10. Prior to implementation of Covered Activities within the Preserve or on vacant lots abutting the
Preserve (see Section 5.6) that may impact Covered Species or their habitat, the City will provide
an education program to all personnel associated with project activities. The education program
will describe 1) the potential presence of Covered Species and their habitats, 2) the requirements
and boundaries of the project (e.g., areas delineated on maps and by flags or fencing), 3) the
importance of complying with avoidance and minimization measures, 4) environmentally
responsible construction practices, 5) identification of sensitive resource areas in the field, and 6)
problem reporting and resolution methods.
11. Any biologist used for the implementation of this NCCP/HCP, including implementing these
measures, will be subject to the Wildlife Agencies’ review and approval. The City will submit the
biologist’s name, address, telephone number, résumé, and three references (i.e., the names and
contact information of people familiar with the relevant qualifications of the proposed biologist) at
least 10 working days prior to initiating work. If the Wildlife Agencies do not respond within this
10-day period, the City will assume that the biologists are approved.
12. For bird species that are not federally listed or Covered by the NCCP/HCP, if vegetation clearing
must occur in the Preserve during the bird breeding season under the circumstances described in
Sections 5.6.9 and 5.6.10 below (defined here as February 15-August 31), a pre-construction nest
survey will be conducted and a 100-feet avoidance/exclusion zone or a buffer/barrier zone to
attenuate noise deemed appropriate by the Wildlife Agencies will be placed around all active nests
(i.e., active nests with eggs or chicks) until the nestlings fledge or the nest fails. Further, no take of
Fully Protected Species is allowed under this Plan (see Section 1.2.2 of the Plan).
13. Covered Plant Species and cacti may be removed from impact areas and relocated to an adjacent
or suitable location within the Preserve, in coordination with the Wildlife Agencies. The City and
its Habitat Manager shall be notified at least ten (10) working days prior to impacts for potential
salvaging and relocation opportunities.
14. No new lighting shall be allowed in the Preserve except where essential for roadway, facility use,
and safety and security purposes. New light sources abutting the Preserve will be oriented
downward and away from habitat areas, and shielded, if necessary, so that the lighting does not
impact wildlife and native vegetation.
15. Construction surveys for herpetofauna shall be conducted prior to and during the first days of initial
grading in areas within the Preserve where significant populations are known to exist. The City, its
Preserve Habitat Manager, and the Wildlife Agencies shall be notified of all findings and relocation
efforts at least ten (10) working days after grading has occurred. Any relocation efforts shall also
be reported in the City’s Annual Report.
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16. Pre-construction surveys for raptor during the breeding season (January 31-September 30), where
evidence of suitable nesting habitat is present, shall be conducted by a qualified biologist no later
than four days prior to any project vegetation removal or grading activities within or on vacant lots
abutting the Preserve. If nesting raptors are present, a 500-foot avoidance/exclusion zone or a
buffer/barrier zone to prevent disturbance and attenuate noise will be placed around all active nests
(i.e., active nests with eggs or chicks) and monitored until the nestlings fledge or the nest fails. If
requested by the City or other entity, the qualified biologist may evaluate site conditions and
determine that nest-specific buffers which vary from the avoidance/exclusion zone above are
warranted based on topography, vegetation, type and duration of activity, and other factors. The
Wildlife Agencies, in coordination with the City and qualified biologist, will be notified of the
status of all raptor surveying and monitoring, including if less than 500-foot avoidance/exclusion
zone or buffer/barrier zone is proposed for the raptor species and what additional
measures/monitoring are necessary. No take of Fully Protected Species is allowed under this Plan
(see Section 1.2.2).
17. All project landscaping, erosion control and re-vegetation efforts within the Preserve shall use
locally collected native vegetation/landscaping to the extent practicable and avoid those species
listed on the California Invasive Plant Council’s (Cal-IPC) Invasive Plant Inventory (see Section
5.6.4 and Appendix D of the Plan). All project landscaping, erosion control and re-vegetation
efforts on vacant land abutting the Preserve are permitted to use non-native plants but shall be
prohibited from using those species listed on the California Invasive Plant Council’s (Cal-IPC)
Invasive Plant Inventory (see Section 5.6.4 and Appendix D of the Plan). This requirement shall be
incorporated as enforceable conditions in all City permits, operations, and authorizations to proceed
with work.
18. Any proposed new or re-located trail within or abutting the Preserve shall comply with the
requirements of the approved PUMP and this Plan. The design criteria and guidelines in Section
9.2.1.1 of this Plan shall be used by the City and its Preserve Habitat Manager in implementing the
PUMP, including the Preserve Trail Plan component. These guidelines place an emphasis on
avoiding or minimizing impacts to CSS habitat and Covered Species, including: 1) providing a
25-foot setback to coastal bluffs; 2) using existing access roads wherever practical; 3) any new
trails, shall be located in areas that minimize habitat fragmentation and edge effects (e.g., maximum
of 4 foot-wide in core areas); 4) seasonally rotating or limiting use to minimize degradation; and
5) providing a 30-foot upland buffer along major drainages.
19. For Covered Projects/Activities within the Preserve, the impact area (see Table 5-1, Total Loss of
Habitat by Covered City Projects and Activities) shall be located on the least sensitive portions of
the site as determined by existing site-specific biological and supporting information, and guided
by the following (in order of increasing sensitivity):
a) Areas devoid of vegetation, including developed areas, previously graded areas, disturbed and
ruderal areas, and active agricultural fields;
b) Areas of non-native vegetation, disturbed habitats, manufactured slopes, landscaped areas and
eucalyptus/exotic woodlands (provided impacts to nesting birds are avoided);
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c) Areas of grasslands (excluding native grassland);
d) Areas containing coastal scrub and saltbush scrub communities and all wetlands, including
riparian scrub;
e) Areas containing southern cactus scrub, southern coastal bluff scrub, cliff face, rock shore and
native grassland communities;
f) Occupied habitat for Covered Species and hostplants for the Covered butterfly Species; current
surveys will be conducted throughout potential Covered Species habitat prior to any Covered
Projects or Activities to assess occupancy and determine avoidance and minimization
measures; and,
g) Areas necessary to maintain the viability of wildlife corridors.
5.6 Avoidance and Minimization Measures for Covered Species
The City will ensure implementation of the following avoidance and minimization measures as enforceable
conditions in all permits, operations, and authorizations to proceed with the Covered Projects and Activities
listed in Sections 5.2 through 5.4 of this Plan. Species-specific conservation measures for covered species
are described in detail in Appendix B and summarized here. These measures are required to maintain permit
coverage for each species.
5.6.1 Aphanisma
Surveys will continue to be conducted every 3 years within the existing fixed locations (PVPLC 2013), and
the Preserve Manager will evaluate potential habitat restoration or enhancement opportunities as part of
routine habitat management. Habitat restoration, including clearing of ice plant or other exotic plants
adjacent to populations, unauthorized trail closures, and seeding for aphanisma will be included in the
PHMP.
Pre-project surveys will be conducted throughout potential aphanisma habitat prior to approving Covered
Activities to assess occupancy and to determine avoidance and minimization measures. If an existing
population will be impacted by Covered Projects/Activities, the project applicant will engage the Preserve
Manager and work with the Wildlife Agencies to prepare and implement a habitat restoration plan, to be
approved by the City and Wildlife Agencies that will ensure no net loss of aphanisma within the population.
Habitat restoration will include use of seed collected from the project site or from previously collected seed.
Impacts to newly discovered or established populations throughout the Plan Area will be offset with
equivalent habitat restoration. No more than two populations will be impacted unless additional populations
are located or successfully established in advance of the impact, and the City, PVPLC and Wildlife
Agencies, through annual coordination meetings, document that the status of the species in the Preserve is
stable and adequately conserved. Trails will be maintained, posted and patrolled to avoid/minimize
encroachment into occupied habitat.
5.6.2 South Coast Saltscale
Surveys will continue to be conducted every 3 years within the existing fixed locations (PVPLC 2013), and
the Preserve Manager will evaluate potential habitat restoration or enhancement opportunities as part of
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routine habitat management. Habitat restoration, including clearing of ice plant or other exotic plants
adjacent to populations, unauthorized trail closures, and seeding for south coast saltscale will be included
in the PHMP.
Pre-project surveys will be conducted throughout potential south coast saltscale habitat prior to approving
Covered Projects/Activities to assess occupancy and to determine avoidance and minimization measures.
If an existing population will be impacted by Covered Projects/Activities, the project applicant will engage
the Preserve Manager and work with the Wildlife Agencies to prepare and implement a habitat restoration
plan, to be approved by the City and Wildlife Agencies that will ensure no net loss of south coast saltscale
within the population. Habitat restoration will include use of seed collected from the project site or from
previously collected seed. Impacts to newly discovered or established populations throughout the Plan Area
will be offset with equivalent habitat restoration. No more than one population will be impacted unless
additional populations are located or successfully established in advance of the impact, and the City,
PVPLC and Wildlife Agencies, through annual coordination meetings, document that the status of the
species in the Preserve is stable and adequately conserved. Trails will be maintained, posted and patrolled
to avoid/minimize encroachment into occupied habitat.
5.6.3 Catalina Crossosoma
Surveys will continue to be conducted every 3 years within the Preserve by the Preserve manager to monitor
trends in population dynamics. Potential for habitat restoration actions that may benefit this species will be
evaluated during routine habitat management. There are no Covered Projects/Activities with the potential
to impact existing populations. If the large population in the Forrestal Reserve expands into an existing
trail, routine trail maintenance as contemplated in the PUMP may require trimming or selective removal of
some Catalina crossosoma individuals, only to the extent that it will maintain the existing width of an
existing trail; impacts from the widening of an existing trail or a new trail would be subject to the conditions
below.
Pre-project surveys will be conducted in potential Catalina crossosoma habitat prior to any Covered
Projects/Activities to assess occupancy and determine avoidance and minimization measures. If an existing
population will be impacted by Covered Projects/Activities, the project applicant will engage the Preserve
Manager and work with the Wildlife Agencies to prepare and implement a habitat restoration plan, to be
approved by the City and the Wildlife Agencies that will ensure no net loss of Catalina crossosoma within
the population. Habitat restoration will include transplantation or use of seedlings propagated from
previously collected seed. Impacts to newly discovered or established populations throughout the Plan Area
will be offset with equivalent habitat restoration. No more than one population will be impacted unless
additional populations are located or successfully established in advance of the impact, and the City,
PVPLC and Wildlife Agencies, through annual coordination meetings, document that the status of the
species in the Preserve is stable and adequately conserved. Trails will be maintained, posted, and patrolled
to prevent/minimize encroachment into occupied habitat.
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5.6.4 Island Green Dudleya
Surveys will continue to be conducted every 3 years within established locations to monitor trends in
population dynamics, and potential habitat restoration actions that may benefit this species will be evaluated
during routine habitat management.
Pre-project surveys will be conducted within potential island green dudleya habitat prior to any Covered
Project or Activity to assess occupancy, and to determine avoidance and minimization measures. If this
species is detected during surveys, impacts to this plant are expected to be avoided. Where avoidance of
island green dudleya is not feasible, the project applicant will engage the Preserve Manager and work with
the Wildlife Agencies to prepare and implement a habitat restoration plan, to be approved by the City and
Wildlife Agencies, that will ensure the impacts will be offset with equivalent habitat restoration. No more
than 0.25 acre of occupied dudleya habitat will be impacted and no more than one impact per Reserve,
unless additional populations are located or successfully established in advance of the impact, and the City,
PVPLC and Wildlife Agencies, through annual coordination meetings, document that the status of the
species in the Preserve is stable and adequately conserved. The PVPLC has a successful propagation
program for this species at the PVPLC nursery, and this program will continue as part of the NCCP/HCP.
This species can be successfully planted in suitable habitat. Trails will be maintained, posted, and patrolled
to avoid/minimize encroachment into occupied habitat.
5.6.5 Santa Catalina Island Desert-Thorn
Surveys will continue to be conducted every 3 years within established locations to monitor trends in
population dynamics, and potential habitat restoration actions that may benefit this species will be evaluated
during routine habitat management.
Pre-project surveys will be conducted within potential Santa Catalina Island desert-thorn habitat prior to
any Covered Project or Activity to assess occupancy, and to determine avoidance and minimization
measures. If this species is detected during surveys, impacts to this plant are expected to be avoided. If an
existing population will be impacted by Covered Projects/Activities, the project applicant will engage the
Preserve Manager and work with the Wildlife Agencies to prepare and implement a habitat restoration plan,
to be approved by the City and the Wildlife Agencies that will ensure no net loss of Santa Catalina Island
desert-thorn within the population. Habitat restoration will include transplantation or use of seedlings
propagated from previously collected seed. Impacts to newly discovered or established populations
throughout the Plan Area will be offset with equivalent habitat restoration. No more than one population
will be impacted, unless additional populations are located or successfully established in advance of the
impact, and the City, PVPLC and Wildlife Agencies, through annual coordination meetings, document that
the status of the species in the Preserve is stable and adequately conserved. The PVPLC has a successful
propagation program for this species at the PVPLC nursery, and this program will continue as part of the
NCCP/HCP. This species can be successfully planted in suitable habitat. Trails will be maintained, posted,
and patrolled to avoid/minimize encroachment into occupied habitat.
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5.6.6 Wooly Seablite
Surveys will continue to be conducted at fixed locations every 3 years within the Preserve by the Preserve
Manager to monitor trends in population dynamics, and potential habitat restoration actions that may benefit
this species will be evaluated during routine habitat management activities. Pre-project surveys will be
conducted within potential woolly seablite habitat for any Covered Project to assess occupancy and
determine avoidance and minimization measures. For Covered Projects/Activities, this species will be
avoided from areas to be impacted, if feasible. The project applicant will engage the Preserve Manager and
work with the Wildlife Agencies to prepare and implement a habitat restoration plan, to be approved by the
Wildlife Agencies, that will ensure the impacts will be offset with equivalent habitat restoration. No more
than 0.25 acre of occupied woolly seablite habitat will be impacted, and no more than one impact per
Reserve, unless additional populations are located or successfully established in advance of the impact,
and/or the City, PVPLC and Wildlife Agencies, through annual coordination meetings, document that the
status of the species in the Preserve is stable and adequately conserved. Trails will be maintained, posted
and patrolled to avoid/minimize encroachment into occupied habitat.
5.6.7 El Segundo Blue Butterfly
Surveys will be conducted by the Preserve Manager every 3 years within the existing populations (Figure
2) to monitor trends in population dynamics. The Preserve Manager shall evaluate potential opportunities
to expand this species’ habitat. The host plant for this species will be included in the seed mix for restoration
(active planting) within the Preserve in suitable areas, particularly in areas similar to the existing known
ESB locations.
Pre-project surveys will be conducted throughout the project area in potential ESB habitat, defined by
presence of coast buckwheat, prior to any Covered Activity to assess occupancy and determine avoidance
and minimization measures. Occupied ESB habitat will be defined by the extent of host plants in an area
known to be occupied by ESB (i.e., any coast buckwheat within 50 feet of a shrub where ESB were
observed), and impacts to occupied habitat will be avoided if possible. Where ESB is detected and impacts
are unavoidable, the Wildlife Agencies will be provided the opportunity (with sufficient advanced notice)
to relocate any and all larvae, pupae, or adults. Survey data will be used to assess the distribution of ESB
within the host plant patch, and the City will work with the Wildlife Agencies to minimize impacts to ESB.
No more than 5% of any existing ESB occurrence polygon will be impacted. Impacts to newly discovered
or established occupied habitat patches will not exceed 10% of their distribution at the time of impact based
on a habitat evaluation conducted within 1 year of the anticipated impact. For any impact to occupied
habitat, host plants will be established onsite to offset the number of host plants lost during the project.
Trails will be maintained, posted and patrolled to avoid/minimize encroachment into occupied habitat.
5.6.8 Palos Verdes Blue Butterfly
The PVPLC shall regularly evaluate potential opportunities to expand this subspecies’ habitat. The host
plant for this species will be included in the seed mix for restoration (active planting) within the Preserve
in suitable areas within coastal sage scrub and grassland habitat, particularly in historic areas. Pre-project
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host plant surveys will be conducted in potential PVB habitat prior to any Covered Project/Activities to
assess occupancy and determine avoidance and minimization measures. If host plants are identified, a 5-
foot buffer around host plants will be avoided if feasible. If avoidance of host plants is not feasible, focused
PVB surveys will be conducted. If PVB is discovered during surveys, the Wildlife Agencies will be
provided the opportunity (with sufficient advanced notice) to relocate any and all larvae, pupae, or adults.
Occupied PVB host plants will be avoided when possible. Occupied habitat will be defined as host plants,
including a 5-foot buffer, within a 50-foot buffer around any PVB observation. Trails will be maintained,
posted and patrolled to avoid/minimize encroachment into occupied habitat. Because PVB host plants
readily establish in disturbed areas, they may become established in trails and dirt roads throughout the Plan
Area. Routine trail and road maintenance may impact host plants and potentially PVB individuals, and there
will be no additional restrictions placed on trail or road maintenance based on presence of PVB.
5.6.9 Coastal California Gnatcatcher
Surveys will be conducted every 3 years within the Preserve to monitor trends in population dynamics and
to evaluate potential habitat restoration actions to benefit this species. The Preserve Manager shall regularly
evaluate potential opportunities to expand and enhance gnatcatcher habitat, and the Plan will provide a net
increase in gnatcatcher habitat within the Preserve. Implementation of species-specific management actions
as part of the PHMP (e.g., invasive species removal) will also occur under the Plan.
Pre-project surveys will be conducted in areas that contain potential gnatcatcher habitat. Construction for
Covered Projects and Activities that may impact gnatcatchers will be scheduled to avoid the bird breeding
season (February 15-August 31). If, due to an urgent or emergency public health or safety concern
determined by the City and Wildlife Agencies, these activities must occur from February 15-August 31
within and/or adjacent to gnatcatcher habitat, gnatcatcher pre-project surveys will be conducted to
determine nesting activity. Survey results will be submitted to the Wildlife Agencies for review. If nesting
activity is detected, then all construction activity must occur outside of a 300-foot buffer surrounding each
nest. Reductions in the nest buffer may be possible depending on site-specific factors (e.g., topography,
screening vegetation, ambient noise levels, etc.), in coordination with the Wildlife Agencies. Construction
noise levels should not exceed 60 dBA Leq within the 300-foot buffer zone unless authorized by the
Wildlife Agencies. The buffer zones and noise limits will be implemented until the nestlings fledge or the
nest fails. Status of the nest will be monitored by a qualified biologist. A report will be submitted to the
Wildlife Agencies for review prior to discontinuing the noise limits and nest buffers. If grubbing or other
construction related activities associated with Miscellaneous Drain Repair, Palos Verdes Drive South Road
Repair, or Alta Vicente Reserve (Upper Point Vicente) must occur from February 15-August 31 within
and/or adjacent to gnatcatcher habitat, gnatcatcher pre-project surveys will be conducted to determine
nesting activity. If nesting activity is detected, all construction activity must occur outside of a 50-foot
buffer surrounding each nest. Construction noise levels should not exceed 65 dBA Leq within the 50-foot
buffer zone. The buffer zones and noise limits will be implemented until the nestlings fledge or the nest
fails. Status of the nest will be monitored by a qualified biologist. A report will be submitted to Wildlife
Agencies for review prior to discontinuing the noise limits and nest buffers. Trails will be maintained,
posted, and patrolled to avoid/minimize encroachment into suitable habitat.
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5.6.10 Cactus Wren
Surveys will be conducted every 3 years by the Preserve Manager within the Preserve to monitor trends in
population dynamics and to evaluate potential habitat restoration actions that may benefit this species. The
Preserve Manager shall evaluate potential opportunities to expand and enhance cactus wren habitat, and the
expectation is that the Plan will increase cactus wren habitat within the Preserve. Implementation of species-
specific management actions as part of the PHMP (e.g., invasive species removal, cactus planting) will also
occur under the Plan, which will protect and enhance existing habitat.
Pre-project surveys will be conducted in areas that contain potential habitat for the cactus wren.
Construction or constructions related activities for Covered Projects and Activities that may impact cactus
wrens will be scheduled to avoid the bird breeding season (February 15-August 31) and to avoid or
minimize direct impacts to mature cactus (i.e., greater than 1 foot in height), and preferentially avoid the
most mature cactus in a particular stand). If, due to an urgent or emergency public health or safety concern
determined by the City and Wildlife Agencies, these activities must occur from February 15-August 31 and
within 100 feet of any coastal sage scrub and cactus wren pre-project surveys will be conducted to determine
nesting activity. Pre-project surveys will consist of 3 survey days over a one-week period, including one
survey within 3 days of construction. Survey results will be submitted to the City, PVPLC, and Wildlife
Agencies. If nesting activity is detected, then all construction activity must occur outside of a 100-foot
avoidance buffer/barrier zone to attenuate noise surrounding each nest. No birds shall be disturbed or taken.
Construction noise levels should not exceed 65 dBA Leq within the buffer zone. The buffer zones and noise
limits will be implemented until the nestlings fledge. The status of the nest will be monitored, and a report
with recommendations will be submitted to the Wildlife Agencies for review prior to discontinuing the
noise limits and nest buffers.
Other measures in the Plan to conserve populations of cactus wren include the following:
• Trails will be posted and patrolled to avoid/minimize encroachment into occupied cactus wren
habitat;
• Locate new public access points and operational/maintenance activities to minimize/avoid areas
occupied by cactus wren and where large stands of mature cactus (at least 1-3 feet tall) exist within
the Preserve; and,
• Impacts to cacti and other succulents within any required fuel clearing areas shall be minimized to
maintain habitat for the coastal cactus wren and other species. Taller (1-3 feet) cactus that cannot
be avoided should be salvaged where feasible and transplanted to suitable areas within the Preserve.
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5.7 Restrictions and Requirements for Projects/Activities Abutting
and Adjacent to the Preserve
5.7.1 Abutting Development Project Review
In reviewing a proposed new development project that will impact potential Covered Species habitat
abutting the Preserve, avoidance or minimization of impacts to biological resources and retention of native
habitats will be addressed as part of plan design review. The site design review process will consider the
locations of access and staging areas, fire and fuel modification zones, predator and exotic species control,
fencing, signage, lighting, increased stormwater and urban runoff, increased erosion, increased noise levels,
and public access to habitats supporting Covered Species in developing measures to avoid or minimize
impacts to biological resources. Avoidance and minimization measures to reduce or eliminate impacts to
biological resources will be incorporated as enforceable conditions in all City permits, operations, and
authorizations to proceed with work.
5.7.2 Fencing and Lighting
The following practices shall apply to new development projects on vacant lots abutting the Preserve:
Fencing, Barriers, and Edge Treatment
1. Fencing, barriers, or functional edge treatment will be required for all new projects developed on
existing vacant lots abutting the Preserve and shall be designed to prevent intrusion of domestic
animals into the Preserve. This requirement may be waived with written approval from the Wildlife
Agencies.
2. Prohibiting the use of gates, openings, or other entry means in project fencing, barriers and edge
treatment that would allow direct human access to the Preserve, which would degrade the natural
habitat. This requirement may be waived with written approval from the Wildlife Agencies.
Lighting
1. All light sources abutting the Preserve shall be designed and constructed to be oriented downward
and away from habitat areas and shielded, if necessary, to ensure there are no impacts to wildlife
and native vegetation.
2. Lighting in new developments on vacant lots abutting the Preserve shall be avoided and/or
minimized as appropriate through appropriate placement and shielding of light sources in
compliance with the City’s Municipal Code requirements for exterior lighting.
5.7.3 Equestrian Use
Brown-headed cowbirds (Molothrus ater) are parasitic, nonnative species in California that contribute to
the decline of many native bird species. This transient bird species originally followed bison herds and has
adapted to follow domestic European livestock. As a result, any new corral or equestrian facility within the
City that requires the approval of a Conditional Use Permit or Large Domestic Animal Permit by the City and
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is located within 500 feet of the Preserve must have a qualified biologist monitor for cowbirds for three years,
and every third year thereafter, to determine their presence. If cowbirds are present, a cowbird trapping program
and/or other effective measures will be funded and implemented by the applicant.
5.7.4 Landscaping
Landscaping can create conflicts with biological objectives of the Preserve by increasing the potential for
introduction of non-native and invasive plant species in natural areas. These non-native species can displace
native species in natural communities. Horticultural regimes can alter site conditions in the Preserve
adjacent to landscaping by increased runoff, fertilization, pesticides, and other factors, all of which promote
a shift from native to non-native flora. Additionally, the use of native cultivars not collected on site or in
the proximity of the site can create genetic contamination through hybridization. Therefore, the following
practices shall apply to all activities within the Preserve, including new development projects on vacant lots
abutting the Preserve, and shall be incorporated as enforceable conditions in all City permits, operations,
and authorizations to proceed with work.
1. Landscaping shall avoid those species listed on the California Invasive Plant Council’s (Cal-IPC)
Invasive Plant Inventory (see Section 5.6.4 and Appendix D of the Plan).
2. Irrigation shall be designed and maintained to avoid overspray or runoff into the Preserve.
5.7.5 Stormwater and Urban Runoff
New development projects on vacant lots abutting the Preserve approved by the City will include mitigation
measures or other conditions, as appropriate, to reduce the likelihood that a flood would adversely impact
Covered Species and the conserved habitat. As a co-permittee of the RWQCB National Pollution Discharge
Elimination System (NPDES) Permit, the City is required to adopt a Standard Urban Stormwater Mitigation
Plan (SUSMP). The large majority of new development projects and significant redevelopment projects
must meet SUSMP requirements to reduce pollution and runoff flows. The City’s SUSMP includes a list
of recommended source control and structural treatment Best Management Practices (BMPs). Additionally,
City land use policies ensure that land use regulations and public improvements accommodate flood events
that approximate the rate, magnitude, and duration of natural flood flows.
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Daniel B. Stephens & Associates, Inc.
Table of Contents
Section Page
Executive Summary .................................................................................................................... 1
1. Introduction ........................................................................................................................... 1
1.1 Site Background ............................................................................................................ 1
1.1.1 Overview and Problem Statement ....................................................................... 1
1.1.2 Regulatory Background ....................................................................................... 4
1.1.3 Recent Community Involvement ......................................................................... 8
1.2 Project Area Definition ................................................................................................... 9
1.3 Purpose and Overview ................................................................................................. 11
1.4 Document Organization ............................................................................................... 12
2. Summary of Previous Work ................................................................................................. 14
2.1 Historical Documents, 1957-1997 ................................................................................ 14
2.2 1997 Ehlig and Yen Feasibility Study ........................................................................... 17
2.3 2000 Leighton Feasibility Study ................................................................................... 20
3. Physical Characteristics of the PBLC Vicinity ...................................................................... 22
3.1 Topography ................................................................................................................. 22
3.2 Watershed Hydrology .................................................................................................. 24
3.3 Soils ............................................................................................................................. 26
3.4 Geology ....................................................................................................................... 29
3.5 Landslide Characterization ........................................................................................... 31
3.6 Hydrogeology............................................................................................................... 34
3.6.1 Groundwater Recharge ..................................................................................... 35
3.6.2 Groundwater Occurrence .................................................................................. 38
3.6.3 Water Wells ...................................................................................................... 40
3.7 Geotechnical Modeling ................................................................................................ 41
4. Feasibility Study .................................................................................................................. 45
4.1 ARARs ......................................................................................................................... 45
4.1.1 Definitions ......................................................................................................... 45
4.1.2 Identified ARARs ............................................................................................... 46
4.2 Remedial Action Objective ........................................................................................... 47
4.3 General Response Actions .......................................................................................... 48
4.3.1 Subsurface Dewatering ..................................................................................... 49
4.3.2 Stormwater Control ........................................................................................... 49
4.3.3 Enineered Slope Stabilization Measures ........................................................... 51
4.3.4 Eliminate Septic System Discharge ................................................................... 51
4.3.5 Coastal Erosion Control .................................................................................... 52
4.4 Identification and Screening of Technology Alternatives .............................................. 52
4.4.1 Stormwater Control Option 1 – Repair Existing Corrugated Piping System ....... 52
4.4.1.1 Description ..........................................................................................52
4.4.1.2 Screening Summary ............................................................................53
4.4.2 Stormwater Control Option 2 – Install Concrete Channels ................................ 53
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Table of Contents (Continued)
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4.4.2.1 Description ..........................................................................................53
4.4.2.2 Screening Summary ............................................................................53
4.4.3 Stormwater Control Option 3 – Install Liner and Channel System ..................... 54
4.4.3.1 Description ..........................................................................................54
4.4.3.2 Screening Summary ............................................................................54
4.4.4 Stormwater Control Option 4 – Seal Surface Fractures ..................................... 55
4.4.4.1 Description ..........................................................................................55
4.4.4.2 Screening Summary ............................................................................55
4.4.5 Subsurface Dewatering Option 1 – Groundwater Extraction Pits ....................... 55
4.4.5.1 Description ..........................................................................................55
4.4.5.2 Screening Summary ............................................................................56
4.4.6 Subsurface Dewatering Option 2 – Groundwater Extraction Wells .................... 56
4.4.6.1 Description ..........................................................................................56
4.4.6.2 Screening Summary ............................................................................56
4.4.7 Subsurface Dewatering Option 3 – Directional Subsurface Drains .................... 57
4.4.7.1 Description ..........................................................................................57
4.4.7.2 Screening Summary ............................................................................57
4.4.8 Engineering Slope Stabilization - Buttressing (Engineered Fill) ......................... 58
4.4.8.1 Description ..........................................................................................58
4.4.8.2 Screening Summary ............................................................................59
4.4.9 Engineering Slope Stabilization Measures - Mechanically Stabilized Earth
Wall ................................................................................................................... 59
4.4.9.1 Description ..........................................................................................59
4.4.9.2 Screening Summary ............................................................................60
4.4.10 Engineering Slope Stabilization Measures – Drilled Piers (Caissons) ............... 60
4.4.10.1 Description ..........................................................................................60
4.4.10.2 Screening Summary ............................................................................60
4.4.11 Centralized Sewer System ................................................................................ 61
4.4.11.1 Description ..........................................................................................61
4.4.11.2 Screening Summary ............................................................................61
4.4.12 Coastal Erosion Control (Breakwater) ............................................................... 62
4.4.12.1 Description ..........................................................................................62
4.4.12.2 Screening Summary ............................................................................62
4.4.13 Summary of Retained Technologies ................................................................. 62
4.5 Detailed Analysis of Remedial Technologies ............................................................... 62
4.5.1 Concrete Channels ........................................................................................... 63
4.5.2 Liner and Channel System ................................................................................ 64
4.5.3 Seal Surface Fractures ..................................................................................... 65
4.5.4 Groundwater Extraction Wells ........................................................................... 66
4.5.5 Directional Subsurface Drains ........................................................................... 67
4.5.6 Centralized Sewer System ................................................................................ 69
4.6 Preferred Options ........................................................................................................ 70
4.6.1 Description and Conceptual Design .................................................................. 70
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4.6.1.1 Seal Surface Fractures........................................................................71
4.6.1.2 Directional Subsurface Drains .............................................................71
4.6.1.3 Liner and Channel System ..................................................................72
4.6.1.4 Groundwater Extraction Wells .............................................................73
4.6.1.5 Centralized Sewer System ..................................................................74
4.6.2 Data Gaps ......................................................................................................... 74
4.6.3 Pilot Testing ...................................................................................................... 75
4.6.4 Approximate Implementation Costs ................................................................... 75
4.6.4.1 Seal Surface Fractures........................................................................76
4.6.4.2 Directional Subsurface Drains .............................................................76
4.6.4.3 Liner and Channel System ..................................................................76
4.6.4.4 Groundwater Extraction and Monitoring Wells .....................................76
4.6.4.5 Centralized Sewer System ..................................................................77
4.6.4.6 Total Estimated Project Cost ...............................................................77
References ............................................................................................................................... 78
List of Figures
Figure
1 Regional Site Location
2 Aerial Photograph with Geographic Features
3 Landslide Subareas
4 Measured Horizontal Movement, 2013-2014
5 Watersheds
6 Topography
7 Major Utilities
8 Regional Geology
9 Stratigraphic Column, Monterey Formation
10 Onshore/Offshore Faults and Folds
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List of Figures (Continued)
Figure
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Daniel B. Stephens & Associates, Inc.
11 Existing Dewatering Wells
12 Slope Stability Model
13 Modeled Increase in Factor of Safety with Decline in Groundwater Elevation
14 Conceptual Horizontal Drains, Extraction Wells, and Monitoring Wells
List of Tables
Table
1 Applicable or Relevant and Appropriate Requirements (ARARs)
2 Screening Evaluation of Remedial Technologies
3 Detailed Analysis of Remedial Alternatives
4 Approximate Order-of-Magnitude Costs for Preferred Alternatives
List of Appendices
Appendix
A USGS Landslide Types and Processes
B Custom Soil Resource Report for Los Angeles County, California, Southeastern
Part, Portuguese Bend
C Geotechnical Modeling Figures
D Conceptual Liner and Channel Specifications
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Executive Summary
Daniel B. Stephens & Associates, Inc. has prepared this feasibility study (FS) update to address
remediation of ongoing land movement in the Portuguese Bend Landslide Complex (PBLC)
using the results of past environmental, engineering, and hydrogeologic work completed to
address regional slope failure on the greater Palos Verdes Peninsula. This FS is an update to
efforts completed primarily in 1997 and 2000 that characterized the hydrogeologic and
geotechnical conditions driving landslide activity and proposed a variety of various approaches
and technologies to abate slope failure in the PBLC.
Earlier remedies focused, in part, on the removal of subsurface water (groundwater) and the
elimination of continued stormwater loading to groundwater in key areas. Some proposed
recommendations were implemented after the 1997 FS was drafted, including installation of
dewatering wells, mass regrading, and surface water infiltration control with an above-grade
piping system. However, land movement was largely unabated, and slope failure continues
today at rates of up to approximately 8 feet per year. Slope failure is continually managed by a
City of Rancho Palos Verdes (City) maintenance program, with significant cost and effort to
maintain area utilities and the nearby roadway in a functional state. Additional measures,
including a major excavation for a buttress extending nearly half a mile along the coast, were
proposed in 2000, but were not implemented.
This FS focuses on implementing cost-effective technologies as options for the City to consider
regarding storm water control and groundwater extraction to achieve manageable and
sustainable land stability. Other geotechnical engineering solutions, such as buttresses, were
also considered with other options, but were screened out due largely to poor overall
implementability.
The FS remedies focus on the southern PBLC area mainly within the control of the City that is
subject to a relatively high level of land movement, where the surface water drainage currently
is not functioning properly, and where groundwater extraction is most needed. An engineering
analysis and evaluation of the existing stormwater drainage system of this area should be
completed to assist in the design and construction of an updated system to convey runoff to the
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Daniel B. Stephens & Associates, Inc.
ocean and eliminate ponding areas which have been created over the years due to land
settlement. At the same time, efforts need to be made for design and installation of
groundwater extraction drains (horizontal drains or hydraugers). Hydrauger design and
installation can be tested and modified based on results obtained. These horizontal drains could
be installed, for example, into the coastal bluff and extend north under PVDS, and directly drain
into the ocean.
Further, it is recommended to perform an engineering analysis of the watershed including the
northern canyon areas (upper Portuguese, Ishibashi, and Paintbrush Canyons) to identify
where, how and to what extent stormwater infiltrates into groundwater in the PBLC.
Subsequently, efforts could be made for design and installation of an environmentally friendly
flexible liner system in the watershed canyons where the stormwater significantly infiltrates to
groundwater in the PBLC in an attempt to minimize this infiltration and allow the stormwater to
be discharged to the ocean in a controlled manner.
Further, it is recommended to identify existing surface fractures throughout the PBLC area and
install land surface fracture sealing with environmentally friendly material to minimize direct
uncontrolled stormwater infiltration which currently percolates into groundwater. These sealed
surface fractures in the PBLC should be checked and maintained annually prior to the rainy
season.
Sanitary sewer septic system effluent in the upslope areas has long been recognized as a
source of groundwater recharge in the PBLC area that needs to be eliminated. In addition to
the above options, it is recommended that the City consider working with its neighboring city,
Rolling Hills, to construct a centralized sanitary sewer system and a storm water drainage
system for the residential neighborhood at the top of the watershed above the Portuguese,
Ishibashi, and Paintbrush Canyon areas, as well as within the City’s Portuguese Bend
neighborhood.
Importantly, the remedy options identified can be implemented in accordance with the City’s
Natural Communities Conservation Plan/Habitat Conservation Plan (NCCP/HCP). Several
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stormwater control and groundwater extraction remedy elements, as envisioned, can be
designed to be largely integrated into the native habitat.
Estimated order-of-magnitude costs for implementation of the recommended remedies total
approximately $31.3 million, with additional operating, maintenance, and monitoring costs
totaling $22 million approximately over 30 years. Additional hydrogeologic and geotechnical
data will be collected as an integral step leading to final design and implementation. In addition,
remedy construction is proposed to be completed incrementally and iteratively starting with a
pilot test program for directional subsurface drains. Drain pilot testing costs (included in above
estimates) are estimated to total approximately $350,000 over about 12 to 18 months.
Stakeholder participation has been identified as a key pathway to project success and
community acceptance. It is recommended that public workshops be scheduled at various
stages of project implementation which could include the design phase, pre-construction, any
pilot testing implementation and post construction phases of the project.
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1. Introduction
This report has been prepared by Daniel B. Stephens & Associates, Inc. (DBS&A) to present
the methods, results, and conclusions of the Portuguese Bend Landslide Complex (PBLC)
feasibility study (FS) update. This FS update has been completed to summarize the physical
characteristics of the PBLC and vicinity, and to systematically compile historical PBLC
investigation work, related vicinity geologic and hydrologic studies, previous efforts toward
achieving land movement stabilization, and regulatory drivers that will impact implementation of
PBLC stabilization measures. The currently available information has been presented and
analyzed in this FS update in order to identify techniques and technologies that can be
implemented to stabilize the PBLC. PBLC stabilization will be considered achieved when a
significant reduction in land displacement is recorded, as measured by the land survey
monitoring system currently in place or a successor land survey methodology.
The format of this FS broadly follows the U.S. Environmental Protection Agency (U.S. EPA) FS
format (U.S. EPA, 1988) developed under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). That is, this document is a CERCLA-analogue FS.
The time-tested CERCLA FS approach is a systematic, methodical, and thorough concept-level
process widely accepted in the engineering industry to develop, analyze, and select cost
effective mitigation alternatives that can be accepted by federal, state, and local regulators and
community stakeholders.
This introductory section presents site background information, regulatory history, the purpose
and objectives of the FS, and a summary of community involvement opportunities.
1.1 Site Background
1.1.1 Overview and Problem Statement
The PBLC is located along the south central section of the Palos Verdes Peninsula within the
City of Rancho Palos Verdes in Los Angeles County, California. The terminus of the active
landslide complex, and generally the southwest boundary of the PBLC, is the Pacific Ocean. In
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this location, the shoreline runs in a generally northwest to southeast direction along the coastal
coves known as Portuguese Bend on the east and Smuggler’s Cove (Sacred Cove) and
Abalone Cove on the west (Figure 1). Two other prominent features on the coastline at the
terminus of the PBLC are Inspiration Point and the more westerly Portuguese Point. The
eastern border of the PBLC is formed by an approximate line that runs northward from western
Yacht Harbor Drive to the confluence of Ishibashi and Paintbrush Canyons. The northern
boundary of PBLC is a small distance south and subparallel to Burma Road, a trail that was
established along the path of the former proposed Crenshaw Boulevard extension.
Construction for the Crenshaw Boulevard extension was begun in the 1950s but was never
completed. The western boundary of PBLC is an approximate north-south line located a small
distance west of Peppertree Drive in a residential neighborhood. The western boundary
terminates south of Palos Verdes Drive South (PVDS) and west of Portuguese Point.
Ehlig (1992) describes PBLC as being divided into two parts. The main part is described as
moving towards Portuguese Bend (Figure 2). The western segment is described as moving into
Sacred Cove between Inspiration Point and Portuguese Point. The main landslide has an area
of about 190 acres and the western segment has an area of about 70 acres. Later, as reported
by Douglas (2013), the PBLC was further divided into several subslides: (1) inland, (2) eastern,
(3) central, (4) seaward, and (5) western subslides (Figure 3).
Douglas (2013) reports that the PBLC (along with the Abalone Cove landslide to the west of
PBLC) is a reactivated part of an approximate 2-square mile ancient landslide mass termed the
Altamira Landslide Complex on the overall south flank of the Palos Verdes Peninsula. Douglas
(2013) states that the landslide mass is a composite of numerous slides ranging from small
slumps to large translational block slides that have occurred over the last approximately
800,000 years. Contrary to this view, Ehlig (1992) states that the slide originated about
120,000 years before present and was a megaslide that started moving as a unit but
fragmented as movement progressed. A guide to landslide terminology, such as earthflow or
landslide complex, is included as Appendix A for reference.
Regardless of the original movement of the larger landslide mass, in 1955, reactivation of the
PBLC was initiated when Los Angeles County was constructing an extension to Crenshaw
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Boulevard with the goal of extending the road down the south side of the Palos Verdes Hills to
an intersection with PVDS. A relatively small landslide was triggered in 1956 during the road
construction, and approximately 160,000 cubic yards of material was removed and placed at the
head of the PBLC. MacKintosh and MacKintosh (1957) concluded that the sliding area had a
very low factor of safety (FOS) prior to movement in 1955, and that the immediate cause of
movement in 1956 and 1957 was the placement of approximately 3 million cubic feet of fill upon
which to build the Crenshaw Boulevard extension. Consistent with antecedent instability noted
by MacKintosh and MacKintosh (1957), Douglas (2013) reported that evidence of movement in
historical aerial photographs had been discovered as early as 1948, and slide damage to the
Portuguese Bend Club pier had been noticed as early as 1946. MacKintosh and MacKintosh
(1957) observed that the most rapidly moving portion of the slide, on the eastern side of the
slide, traveled about 22 feet in the seven months between September 17, 1956 and April 26,
1957.
Douglas (2013) reported at the time of Crenshaw Road extension project that houses in the
area were using septic waste systems that recycled household water into the subsurface, and
that the neighborhoods did not have storm drains. Both of these factors had been contributing
to groundwater recharge in the PBLC area by the time the road construction began. Douglas
(2013) also stated that Converse Consultants concluded that increased pore water pressure
that resulted from elevated groundwater levels was a significant causal factor.
Since the reactivation in 1956, the slide has moved at various rates. In general, the area of
greatest movement has stayed the same and is focused in the eastern and seaward subslide
areas as reported by Douglas (2013) and described above. Figure 4 presents a map of the
horizontal displacement that occurred between October 8, 2013 and September 19, 2014.
Horizontal displacement of over 8.5 feet per year was measured within the eastern and seaward
subslides.
Continued land movement in the PBLC area over the last several decades has resulted in
significant infrastructure damage to homes, utilities, and roadways. The City of Rancho Palos
Verdes has expended nearly 50 million dollars over the years repairing and maintaining the
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damage and addressing the overall technical and administrative issues associated with
managing such a complex problem.
1.1.2 Regulatory Background
Historically, the primary driving force for conducting projects to stabilize the PBLC has not been
of regulatory origin. Preservation of infrastructure, preservation of private property, preservation
of open lands, preservation of the natural vegetation and recreational attributes of the Palos
Verdes Nature Preserve (Preserve), reduction in soil erosion losses, restoring the water clarity
in Portuguese Bend Cove, reduction in the cost of operation and maintenance of infrastructure,
and health and safety concerns related to maintenance of the integrity of the key road system,
the sewer system, and other infrastructure have been the leading drivers that have motivated
the City of Rancho Palos Verdes and citizens to strive to achieve stabilization of the PBLC. As
a result, there is little in the record that involves regulatory action with respect to the PBLC.
Nonetheless, the following is a summary of applicable regulatory based actions taken relative to
historical PBLC projects that may influence future work in the PBLC.
In September 1987, the Rancho Palos Verdes Redevelopment Agency (RDA) proposed a
grading and drainage project as part of a series of projects designed to contribute to the
stabilization of the PBLC. The project was examined on a general basis in previous
environmental impact reports (EIRs) prepared by the RDA. This particular EIR provided an
analysis of environmental impacts associated with grading, drainage, and relocation of PVDS.
The final proposed project incorporated alterations that mitigated non-significant short-term
negative impacts.
The Community Development Commission for the County of Los Angeles also completed a
National Environmental Policy Act (NEPA) environmental assessment and the project was
found to be in compliance with applicable laws and regulations and did not require an
environmental impact statement (EIS). A finding of no significant impact (FONSI) was made
stating that the project would not significantly affect the quality of the human environment (City
of Rancho Palos Verdes, 1987).
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In 1988, a general investigation study by the U.S. Army Corps of Engineers (USACE) was
authorized by Public Law 99-662, Section 712 of the Water Resources Development Act of
1986, to study the feasibility of constructing shoreline erosion mitigation measures in order to
provide additional stabilization for the PBLC and adjacent landslide areas (USACE, 1998). The
authorization read that the Army was “. . . authorized to study the feasibility of constructing
shoreline erosion mitigation measures along the Rancho Palos Verdes coastline and in the City
of Rolling Hills, California for the purpose of providing additional stabilization for the Portuguese
Bend landslide area and adjacent landslide areas.”
The study focus was on controlling sedimentation and turbidity in the nearshore and offshore
zones that result from erosion at the shoreline, which impacts the marine species and habitat of
the area. Additional fish and wildlife enhancement studies were authorized in the Water
Resources Development Act of 1990, Section 116 which read “. . . investigative measures to
conserve fish and wildlife (as specific in Section 704 of the Water Resources Development Act
of 1986), including measures to demonstrate the effectiveness of intertidal marine habitat.” The
reconnaissance study was initiated in October 1988 and completed in 1990, with a
recommendation to proceed to a feasibility study based on a plan to help stabilize the landslide.
However, a decision by the Assistant Secretary of the Army stated in a letter dated October 28,
1991 that “Landslide stabilization is outside the purview of the Army Civil Works program.” The
reconnaissance report was revised in 1992 to reflect that decision, and no further study was
recommended.
In anticipation of another proposed Portuguese Bend Grading Project located within the City of
Rancho Palos Verdes Redevelopment Area, an initial study was prepared in September 1994 in
accordance with the provisions of the California Environmental Quality Act of 1970 (CEQA) as
amended (Public Resources Code Section 21000 et seq.), and the State CEQA Guidelines for
Implementation of the California Environmental Quality Act of 1970 as amended (California
Code of Regulation Section 15000 et seq.). The project site was comprised of three vacant
non-contiguous areas located on the eastern portion of the PBLC.
This report of the initial study complied with the rules, regulations, and procedures for
implementation of CEQA adopted by the City of Rancho Palos Verdes (the Local CEQA
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Guidelines). The project grading activity, specifically cutting and filling within the PBLC,
proposed the removal of approximately 50,000 cubic yards of earth material from a cut area
approximately 6.25 acres in size located in the southeastern portion of the PBLC. The project
also proposed redistribution of the 50,000 cubic yards of earth material to two previously
graded/disturbed fill areas. The reported purpose of the proposed project was to reduce driving
forces in an active portion of the PBLC by moving earth from a driving force area to a neutral
area of driving force (EDAW, 1994).
In accordance with Section 15050 and 15367 of the State CEQA Guidelines, the City of Rancho
Palos Verdes was designated as the lead agency, defined as the public agency that has the
principal responsibility for carrying out or approving a project. The project was funded by the
RDA and implemented by the City working for the RDA. After implementation of the initial
study, it was concluded that although the proposed project could have a significant effect on the
environment, there would not be a significant effect in this case because of mitigation measures
that were added to the project. As a result, a mitigated negative declaration was prepared.
Mitigations required as a component of the approved project included the following:
• Control of construction-generated dust
• Cessation of vehicular traffic when the wind speed exceeds 15 miles per hour (mph)
• Appropriate NOx emission controls on construction vehicles
• Minimization of footprint for construction vehicle routes
• Identification of optimum construction vehicle routes to avoid areas of sensitive
vegetation
• Preparation and review of erosion control plans by the Director of Public Works and a
qualified biologist to protect sensitive plant species and minimize disturbance to non-
sensitive plant species
• Post-construction re-establishment of vegetation
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• Prohibition of grading/construction during the mating/breeding/nesting season for the
California gnatcatcher and the coastal cactus wren (mid-February through July)
• Limitation of construction hours to Monday through Saturday, 7:00 a.m. to 5:00 p.m.
(noise control)
• Equipment of construction equipment with mufflers (noise control)
An extensive biological assessment of the Rancho Palos Verdes development area was
attached to the study that was based on a literature review and field surveys of the study area
and, in some cases, surrounding areas. It is noteworthy that the study concluded that the
proposed project would not impact the quality of existing recreational opportunities and that the
project was not located in an area of existing recreational use, or designated for recreational
activity. That conclusion may require re-evaluation to consider current uses of the area.
Another initial study to evaluate a proposed erosion control project was conducted in 1994
(EDAW, 1994). The proposed project consisted of the placement of three drainage inlets and a
48-inch corrugated metal pipe (CMP) at the bottom of Portuguese Canyon, from PVDS to a
point in the canyon approximately 1,600 feet north of PVDS. Approximately 350 linear feet of
1211 CMP was to be placed on the surface and staked down at each joint or at intervals not to
exceed 15 feet.
The proposed project also involved minor grading and brush removal at the bottom of the
canyon, as necessary for installation of the drainage pipe and inlets. A finding was issued that,
although the proposed project could have a significant effect on the environment, there would
not be a significant effect because the mitigation measures described on an attached sheet
have been added to the project. Preparation of a negative declaration was recommended
(EDAW, 1994).
Subsequent to the Secretary of the Army declining to participate in a landslide study, Congress
added funds for a feasibility study to develop a shore protection project that would provide for
restoration of the natural marine habitat at Rancho Palos Verdes. An agreement between the
City of Rancho Palos Verdes and the USACE to perform the study was signed in December
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1994. The alternative selected as the proposed recommended plan in the feasibility study was
to construct a dike 400 feet offshore with natural removal of sediment deposits in the restoration
area by wave action.
1.1.3 Recent Community Involvement
The Landslide Subcommittee of the Rancho Palos Verdes City Council organized and held a
series of public meetings on June 1, June 20, June 29, and July 6, 2017. The purpose of the
meetings was to invite the community to participate in creating and identifying goals for the
PBLC and to discuss the path forward in addressing the challenges faced by the community
with respect to the PBLC.
At the first public meeting, held on June 1, 2017, goals were identified that included the
following:
• Control of the PBLC and attendant costs
• Stabilize residences
• Retain use of PVDS
• Protect the integrity of the Preserve and preserve the marine ecology
• Restore the ecology of the ocean and land resources
• Explore the possible of a geological hazard abatement district (GHAD)
• Identify plausible potential solutions
• Provide the basis of a design-build proposal to solicit federal funding
The June 20, 2017 public meeting focused on potential solutions and/or actions for intercepting
water on the PBLC. The meeting discussions were wide-ranging, and emphasized (1) the need
to fully understand the hydrology of the watershed in which the PBLC is located, (2) the need to
re-establish and maintain an effective stormwater control system, (3) the importance of
capturing and controlling water before it gets into the PBLC, and (4) to minimize impacts to
Preserve land.
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The June 29, 2017 public meeting addressed the effects of the PBLC on the surf zone.
Consensus of the participating public focused on (1) hiring competent engineers to implement
recommendations, (2) early communication with relevant regulatory agencies (e.g., Coastal
Commission) regarding any planned PBLC projects, (3) use of road maintenance funds to
underwrite the necessary technical work needed to slow the PBLC movement, and
(4) assessment of the environmental impacts to the Preserve land and ocean ecology plus
restoration of potentially damaged habitat to its original condition.
The July 6, 2017 meeting focused on major actions that could be considered as a means of
addressing the PBLC problem. As with a previous meeting, the public consensus focused on
understanding the hydrology of the PBLC, understanding the occurrence of groundwater as it
relates to the movement of the PBLC, and understanding and completing previous work on
surface drainage.
On October 17, 2017, a meeting was held between representatives of the City, DBS&A, the
PVPLC, and the Wildlife Agencies to discuss potential impacts of PBLC solutions within the
context of the City’s draft Natural Community Conservation Plan/Habitat Conservation Plan
(NCCP/HCP). The City’s goal for the meeting was to develop a programmatic policy ensuring
that, while the probability for successfully resolving the PBLC problem was maximized, all
appropriate measures were being considered to minimize potential impacts to biological
resources within the Preserve.
1.2 Project Area Definition
This FS focuses on significantly reducing land movement in the defined Red Zone area (project
area) of the PBLC, where land movement has consistently been measured at the greatest rates.
As shown in Figure 2, in addition to PBLC, landslides in the southern Palos Verdes Peninsula
include the Abalone Cove, Portuguese Bend, Flying Triangle, Klondike Canyon, and most of the
Ancient Altamira Landslide. All of these landslides are located within the City of Rancho Palos
Verdes except for the majority of the Flying Triangle Landslide, which is in Rolling Hills.
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As described by Douglas (2013), two of the landslides, Portuguese Bend and Abalone Cove,
are reactivated parts of a much larger and older slide mass that covers over 2 square miles and
extends from the crest of the peninsula, near Crest Road, to the shoreline. Douglas (2013)
named this ancient landslide mass the “Ancient Altamira Landslide Complex.”
Douglas (2013) reported that the Abalone landslide and surrounding area, including portions of
the ancient landslide complex, has been largely stabilized through the use of groundwater
dewatering using vertical wells. The Klondike and Flying Triangle Landslides are closely related
in space and time to the PBLC and Abalone Landslides, and are also part of the Ancient
Altamira Landslide Complex, but they are commonly considered separate failures (Douglas,
2013).
The PBLC project area within which land movement is being addressed by this FS is the area of
greatest movement within the PBLC. As shown in Figure 4, the area in which measured
horizontal movement has ranged from 1 foot, 10 inches to 8 feet, 7 inches is the area of
greatest PBLC movement (the Red Zone). As mapped, the Red Zone is approximately
86 acres in area. This Red Zone area comprises what Douglas (2013) delineated as the
eastern, central, and seaward landslide subareas of the PBLC, along with a small portion of the
western PBLC landslide subarea, south of PVDS to the ocean.
The total PBLC area is approximately 250 acres (101 hectares) in area. However, the area of
land on which conditions that contribute to landslide instability exist is much greater. Numerous
hydrologic, geologic, and engineering reports of the PBLC have concluded that controlling the
water that enters into and is stored in the PBLC subsurface is critical to achieving landslide
stabilization. Therefore, this FS considers that the selected landslide stabilization solution will
be implemented over an area larger than the PBLC or the Red Zone itself. Water can move into
the PBLC subsurface, where it contributes to instability, via three pathways.
The first pathway is via rainfall and stormwater that runs off and subsequently infiltrates and
percolates into the subsurface. W ater is also introduced into the subsurface through residential
use and disposal via onsite wastewater treatment systems (e.g., septic systems), a second
pathway. The third pathway is via groundwater underflow. Groundwater underflow occurs
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when groundwater that has percolated to the water table in one location migrates laterally to
another location. In the PBLC location, previous contouring of groundwater levels indicates that
groundwater is moving in the subsurface from upslope areas to the north of PBLC toward the
south.
As a result, the larger area that is being considered when targeting a PBLC landslide
stabilization solution is the watershed. A watershed is defined as the area of land bounded
peripherally by a divide and draining ultimately to a particular watercourse or body of water. For
example, in Portuguese Canyon, the watershed is defined as the land area from which all water
that drains will ultimately drain into Portuguese Canyon. Based on review of topographic and
drainage maps along with the use of field observations and aerial photographs, subsurface
water in the PBLC is being impacted by water from Portuguese, Ishibashi, and Paintbrush
Canyons. Figure 5 depicts the combined watershed boundary of the three canyons.
1.3 Purpose and Overview
This FS report has been prepared consistent with methodologies that have been developed
pursuant to CERCLA, also known as Superfund. Specifically, this FS was prepared using
methodologies presented in the Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA (U.S. EPA, 1988). The CERCLA FS process is typically
used to abate the risk of exposure to toxic environmental contaminants. In this project, toxic
contamination is not an issue, and the criterion related to reduction of contaminant toxicity is
removed from consideration.
The resulting FS process represents a systematic methodology established for characterizing
the nature and extent of complex problems, evaluating potential remedial options, and selecting
the optimum remedial solution options for the City’s consideration. The overall goal of the FS
process is to gather sufficient information to make an informed management decision regarding
potential remedial actions, and to develop a comprehensive, reliable, restoration strategy that
satisfies community and regulatory requirements. The specific purpose of this FS is to identify
viable conceptual solution options that will accomplish the following project goals:
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• Provide the geotechnical conditions that significantly reduce the risk of damage to public
and private property and would allow for the significant improvement of roadway
infrastructure, safety, and stability.
• Significantly reduce human health risk and improve safety in the City of Rancho Palos
Verdes.
• Significantly reduce sediment dispersal and deposition into the Pacific Ocean that is
causing unacceptable turbidity in the coastal and marine environment.
• Select remedy options that will be consistent with the Natural Communities NCCP/HCP,
specifically Section 4.1.2.
1.4 Document Organization
This FS document generally follows the methodology and organizational format of the CERCLA
feasibility study process (U.S. EPA, 1988). Section 1 presents an introduction that includes
project background, history, project purpose, projection area definition, and a description of
community involvement with the project. Section 2 provides a summary of the relevant previous
work related to the PBLC and vicinity that forms a foundation for moving forward toward remedy
selection and implementation options. Section 3 present a description of the physical
characteristics of the project area including topography, watershed hydrology, soils, geology,
groundwater, and landslide characteristics. Taken together, Sections 1 through 3 represent a
characterization of the current information and data available to use in defining the PBLC setting
and problem.
Using the information and data presented in Sections 1 through 3 as the basis, Section 4
presents the remedial FS section of the report. Sections 4.1 and 4.2 present the introduction
and purpose of the FS and the summary of infrastructure concerns related to the PBLC,
respectively. Section 4.3 presents the applicable or relevant and appropriate requirements
(ARARs) potentially governing remedy implementation. Section 4.4 establishes the remedial
action objectives (RAOs). Section 4.5 establishes general response actions (broad classes of
available technologies) to control movement of the PBLC. Section 4.6 identifies and screens
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the identified technologies appropriate to achieve the RAOs. Section 4.7 provides a more
detailed discussion and analysis, presenting the pros and cons, of the technologies most
suitable to achieve RAOs. Finally, the preferred alternative options are identified in Section 4.8
as the most appropriate technology and methodology to address RAOs. An analysis of
remaining data gaps, the need for pilot testing, and an estimate of the cost of implementation of
the selected remedy are also presented.
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2. Summary of Previous Work
As noted by Douglas (2013), numerous geologic, hydrogeologic, environmental, and
engineering studies have been completed and numerous reports have been produced by
several authors over the years since the PBLC was first recognized. Not all of the documents
have been digitally archived and some information has likely been permanently lost over the
years. However, some key documents are available that describe past efforts and designs for
land stabilization that are useful to review and form a foundation for moving forward toward a
solution. These documents, supplemental to those described in Section 1.1.2, are summarized
below.
2.1 Historical Documents, 1957-1997
In 1957, a report was written that described the ground movement of an approximately 200-acre
area of land extending from above a major body of fill on Crenshaw Boulevard southward to the
Pacific Ocean (MacKintosh, 1957). The report recommended that immediate emergency action
be undertaken “. . . to protect the large investment in homes, streets, sewers, communication
lines, and other utilities and improvements.” As of 1989, over 140 homes have been destroyed.
Of the residents that remain, home utilities and foundation structures must be maintained
continuously. It was also reported that over 10 million tons of mud and rock were deposited in
the ocean. Disruption of vital community transportation and utility transmission lines is
continuously threatened and millions of dollars have been spent to maintain community safety
and services.
Between March and August 1957, the County of Los Angeles and Palos Verdes Properties
installed a group of 22 reinforced concrete caisson “shear pins” across the active failure surface
in an effort to stabilize the PBLC. Each of these caissons was 4 feet in diameter, 20 feet in
length, and embedded 10 feet into the material underlying the “failure surface” as it was
understood at that time. The landslide reportedly slowed by approximately 65 percent (from
0.8 to 0.25 inch per day) following the installation of these shear pins. This reduced rate of
movement was only maintained for approximately five months. In early 1958, the landslide
abruptly returned to its pre-shear pin displacement rate of nearly 0.8 inch per day. Several
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intact shear pins have since been displaced to, and deposited on, the shoreline by subsequent
landslide movement and wave action (Ehlig and Yen, 1997).
From the late 1950s through the mid-1980s a series of geologic and engineering studies were
conducted to understand and characterize various aspects of the PBLC and related landslide
complexes in the vicinity.
In 1972, Palos Verdes Properties provided financial support for a dissertation that analyzed the
reasons for the movement of the PBLC (Vonder Linden, 1972). The report stated that “If
movement were halted by eliminating infiltration of water, lowering the existing water table, and
regrading parts of the slide surface, the factor of safety thereby would be raised to a value of at
least unity.”
The City of Rancho Palos Verdes was incorporated in 1973, and at that time the City took over
the maintenance of roads and utilities in the PBLC area within the City limits. It was reported
that approximately 20 percent of the City budget for street maintenance was spent for the
0.8± mile of PVDS through the landslide (Ehlig and Yen, 1997).
In September 1978, the Rancho Palos Verdes City Council adopted Urgency Ordinance No.
108U, which established the Landslide Moratorium Area in and around the PBLC. In February
1981, the City Council adopted Ordinance No. 139U, which added the area known as Klondike
Canyon to the Landslide Moratorium Area.
In 1984, the City put a landslide stabilization plan of control (POC) into operation. In 1984, it
was reported that the PBLC was moving over 40 feet per year. The stabilization plan consisted
of installation of dewatering wells, major surface drainage, and regrading redistribution of
earthen mass. This initial effort has since been called Phase I (Ehlig and Yen, 1997). It was
reported that 5 years after initiation of the POC, the PBLC was moving less than 1 foot per year.
The RDA proposed a grading and drainage project in September 1987, as Phase II of the POC
intended to stabilize the PBLC (Ehlig and Yen, 1997). The grading portion performed in
January and March 1988 involved redistribution of 500,000 cubic yards of earth from areas
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where the slide plane was steep to areas where the slide plane was relatively level so that the
weight of the landslide material acted as a resisting force rather than a driving force. Generally
speaking, the rate of slide movement responded positively to dewatering, regrading, and
surface drainage improvements in Phase I and II, but these were not ultimately able to stop the
slow movement. In fact, the rate of movement increased in subsequent years as earlier work
deteriorated.
Following a period of severe wave erosion and shoreline regression in early 1988, rock-filled
wire baskets (gabions) were installed along the western shoreline of the landslide in 1988 in an
attempt to reduce the rate of wave erosion. Although this temporarily abated the erosion, the
gabions were essentially destroyed within an 18- to 24-month period by the combination of
wave action, corrosion of the wire baskets, and landslide deformation (Ehlig and Yen, 1997).
In January 1989, the USACE held a public information workshop to present to the community a
study it was beginning in order to identify the federal interest in solutions to problems associated
with shoreline erosion mitigation measures and storm damage along the coast of Rancho Palos
Verdes, including consideration of how such a solution would contribute to landslide
stabilization. In June 1993, the Assistant City Manager of Rancho Palos Verdes wrote a
memorandum describing an upcoming workshop on the RDA’s interaction with the USACE on a
feasibility study for shoreline protection and marine environmental restoration. The discussions
centered on the need for shoreline protection, not landslide abatement.
Phase Ill grading was completed during August and September 1990. This phase of grading
involved the relocation of approximately 60,000 cubic yards of soil from the central uphill margin
of the landslide to the eastern portion of the failure immediately upslope of PVDS. Following
this unloading, perceptible movement of the Landward Zone appears to have stopped until the
heavy rainfall of January 1995. Between the completion of the 1990 Phase III grading and
1995, the rate of landslide movement gradually increased to approximately 0.25 inch per day
(Ehlig and Yen, 1997).
In 1991, Rancho Palos Verdes staff gave a presentation to the City Council on the progress of
the stabilization plan. The progress reported included the performance of extensive geologic
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investigations using the services of 25 experts in the fields of geology and engineering. In
addition, $1.5 million had been spent to implement grading, dewatering wells had been installed,
and drainage structures had been constructed to control and convey water through the PBLC.
In September 1994, a consultant proposed a grading project to the City of Rancho Palos Verdes
in which several areas of the PBLC slide area were identified as “cut” zones where 50,000 cubic
yards was to be removed, and other areas of lower elevation were identified as “fill” zones. As
with the earlier proposed grading project of 1987, the purpose was to reduce driving forces in an
active portion of the PBLC by moving earth from a driving force area to a neutral area of driving
force.
In 1997, the City of Rancho Palos Verdes and the USACE commissioned a study to determine
the impact of the PBLC on the ocean environment (Abbott Associates, 1997) that concluded
that 3,589,000 cubic yards of earth had entered into the ocean as a result of landsliding.
2.2 1997 Ehlig and Yen Feasibility Study
A preliminary geologic and geotechnical engineering report was jointly prepared by Perry Ehlig
(Ehlig) and Bing Yen & Associates, Inc. (BYA) which was presented to the City Council of
Rancho Palos Verdes in 1997. The report evaluated the feasibility of a POC developed in 1995
by Ehlig and BYA and amended it for the 1997 report. The POC was intended to minimize or
arrest the movement of the more rapidly moving portion (East-Central Subslide) of the PBLC
and if successful, would provide valuable insight on the feasibility of stabilizing the western
portion of the PBLC.
The scope of work of the study incorporated compilation and evaluation of the historical surface
and subsurface data to determine where additional exploration was needed to develop a
preliminary geotechnical model for analysis. The study also consisted of installation of
13 additional monitoring wells to characterize groundwater, drilling of 18 large-diameter, 8
rotary-wash, and 4 rotary-core boreholes for subsurface mapping of the slide plane(s), and
collection of slide plane samples for additional laboratory testing. Back calculation of the slide
behavior was performed on the slide model to calibrate the soil parameters and confirm the
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validity of the model. Assessment of the proposed POC in mitigating the slide movement was
done using the model to identify primary and supplemental mitigation techniques and their
effectiveness. Based on the results of the POC assessment, conclusions and
recommendations were presented in a formal report.
Based on movement patterns, geologic, and/or geomorphic features, the PBLC was subdivided
into subslides. The subslides were classified on increasing displacement rates which include,
from the lowest to greatest rate of movement, the Landward, the West-Central, the East-
Central, and the Seaward subslides. The study estimates that for the period from 1956 to 1996,
rates of displacement range of the subslides range from 0.2 to more than 1.5 inches per day,
and that the higher rates are associated with periods of above-average rainfall.
The Ehlig/BYA POC recommended removal of approximately 450,000 cubic yards of slide plane
clay from the upper portions of the Landward and East-Central subslides of the PBLC. This
plan requires the excavation and removal of approximately 2.65 million cubic yards of landslide
materials. They estimate that roughly 100,000 cubic yards of the landslide materials would
consist of bentonitic (slide plane) clay, which could be used as a blanket fill to retard surface
water infiltration. The remainder of the removed materials would be exported off-site and
replaced with compacted fill.
The POC also included installation of subdrain systems in the removal areas, construction of
impervious drainage channels in selected canyons, installation of dewatering wells, and re-
establishment of surface drainage within the developed portion of Portuguese Canyon. The
study evaluated three scenarios where no reduction in groundwater levels occurred, lowering of
the groundwater level of 25 feet, and lowering of groundwater level of up to 35 feet south of the
regraded area. The increase in the factor of safety was estimated to range from 7 percent to
16 percent.
After discussing the benefits of dewatering and its positive effect on increasing the factor of
safety, the report stated:
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However, engineering analysis also revealed that the Seaward subslide, exacerbated by its steep
and dilated bluff and erosion at its toe, will have a lower factor of safety than the regraded
northeast PBL. Hence, the Seaward subslide may move first and, consequently, pose the risk
that the EastCentral subslide may lose its lateral support towards the ocean. Engineering analysis
shows further that the reduction of lateral support will reduce the factor of safety of the East-
Central subslide to 1.04. This means that, while it appears to be theoretically feasible that the
proposed POC [plan of control] can improve the current state of stability in eastern PBL, the
margin of safety for the East-Central subslide (at a factor of safety of 1.04) is too small and the
East-Central subslide will have an intermittent slow movement and periodic acceleration following
heavy precipitation.
Thus, the authors indicate their opinion that the avoidance of the addition of water to the
subsurface in this area is critical. However, the authors stated that even in the best case, the
proposed POC would only be capable of improving the stability marginally and that the landslide
may still creep intermittently and be susceptible to reactivation. Conditions cited which could
contribute to reactivation of the landslide included shoreline erosion, successive years of above
average rainfall, lapses in the de-watering or surface drainage maintenance programs, and
continued movement of the Seaward and/or West-Central subslides. Thus the authors
evaluated supplemental stabilization measures that included (1) slide plane clay strength
enhancement, (2) the construction of a revetment along the shore line, and (3) a more extensive
dewatering program.
The evaluation indicated that the tests conducted for this report regarding slide plane clay
strength enhancement via lime injection were promising but not extensive, nor was the method
of field implementation proven. A pilot test was recommended. The construction of a revetment
along the shore line was assumed to be implemented in combination with strength reduction
due to slow movement. In this scenario, the revetment was deemed a successful approach, but
it was recognized that any construction in the vicinity of the existing shoreline would require
permits from federal and state regulating agencies, and that obtaining these permits might be a
long and costly process with uncertain outcome. Regarding supplemental dewatering, the
authors stated that the benefits of lowering the groundwater elevation would be theoretically
significant, particularly in the eastern portion of the landslide. However, to lower the water table
an average of more than 20 feet may not be feasible because of the high cost associated with
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lowering groundwater within the low permeability material. At the time, the authors believed that
one could not practically expect to lower the water table an additional 20 feet below the October
1996 level across the PBLC as a whole (Ehlig and Yen, 1997).
Ehlig and Yen (1997) also reported on a global positioning system (GPS) satellite survey
network that the City of Rancho Palos Verdes established that showed that the eastern portion
of the slide moving about twice as fast as the western portion. The report stated that the rate
accelerates when groundwater rises and/or when the landward (northern) portion of the slide
exerts additional driving forces due to local slope failures or debris accumulations. Erosion of
the toe of the slide along the shore exacerbates the instability of the seaward portion of the
slide.
2.3 2000 Leighton Feasibility Study
In a report prepared for the Palos Verdes Portuguese Bend Company, Leighton and Associates
(Leighton) (2000) reviewed the 1997 POC (Ehlig and Yen, 1997) and recommended revisions.
The report was prepared for the proposed construction of an 18-hole golf course and related
facilities. The report presented a revised POC termed the Palos Verdes Portuguese Bend
(PVPB) POC. The PVPB POC included all but the lime injection aspects of the 1997 POC,
supplemented with a more extensive removal and capping of the landslide area, and extensive
shear keys, as well as additional subdrains, monitoring wells, and dewatering wells. Grading for
the property, including Peacock Hill and the active PBLC, was presented in a proposed grading
plan. The PVPB POC was planned in phases, sequenced to limit the probability of major
accelerations in the rate of landslide movement.
The scope of work for the study included determination of the subsurface geologic structure, the
ancient and active rupture surfaces, the gross stability of the site, and a groundwater analysis.
The work performed included review of past geological, geotechnical, and hydrogeological
reports and maps, aerial photograph analysis, and geologic mapping of the field area. Analyses
of GPS survey and monitoring well data were also completed for the study. Subsurface
exploration included drilling of 9 large-diameter and 11 continuous-core borings with downhole
wireline geophysical logging, in addition to logging of 3 exploratory trenches. All of the core
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borings were converted to monitoring wells, and 4 additional monitoring wells were constructed
with nests of piezometers. Laboratory testing of slide plane materials was conducted to
establish chemical and physical properties for utilization in the slope stability analyses. Slope
stability analysis was performed of the present stability and to determine the impacts of the
proposed development, and the implementation of the proposed POC was also included.
Other remedial measures proposed by Leighton include construction of two additional large
shear keys to support buttresses of recompacted fill with subdrainage. The largest of the shear
keys was proposed to be constructed near the toe of the PBLC and a toe protection system
consisting of a riprap revetment was also recommended. An elaborate system of subdrainage
of horizontal wells would intercept subsurface flow below Paintbrush and Ishibashi Canyons and
direct flow to the ocean. Also, permeable drainage membranes, remedial grading, and
construction of a drainage culvert would reduce surface water infiltration and facilitate gravity
flow for the subdrainage system. Other remedial measures include more extensive capping of
the landslide area, a short sheet pile wall at the western Klondike Canyon landslide boundary
adjacent to the Beach Club, and construction of a dewatering pit to permit the development of a
system of hydroaugers.
The slope analysis conducted by Leighton estimates that the factor of safety for the most active
portions of the PBLC would increase by approximately 50 percent. The factor of safety for the
less active portions would increase by approximately 20 percent. They also conclude that the
slide movement of the active portions of the PBLC located east of Inspiration Point would be
arrested.
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3. Physical Characteristics of the PBLC Vicinity
This section provides information describing PBLC area topography, hydrology, soils, geology,
and hydrogeology, as well as landslide characteristics.
3.1 Topography
The regional topography of the ancient Altamira Landslide Complex is mapped in the U.S.
Geological Survey (USGS) Redondo Beach, Torrance, and San Pedro quadrangles (USGS,
1963 and 1964). More recently, the Los Angeles Region Imagery Acquisition Consortium (LAR-
IAC) developed a digital terrain model (DTM) using LiDAR and generated 2-foot and 5-foot
digital contour elevation for Los Angeles urban project areas and Catalina Island, which includes
the City of Rancho Palos Verdes (circa 2015) (Figure 6). The PBLC is located in the southeast
portion of the larger and older Altamira Landslide Complex, is completely mapped within the
San Pedro, California quadrangle (USGS, 1964), and is part of the LAR-IAC DTM.
The Altamira landslide covers over 2 square miles extending from the crest of Palos Verdes
peninsula near Crest Road at elevations of approximately 1,200 feet above mean sea level (feet
msl) to the shoreline (Douglas 2013, Vonder Linden 1972). The perimeter of the Altamira
Landslide Complex is generally bounded by an unnamed canyon adjacent to Barkentine
Canyon to the west and the Klondike Canyon to the east and has the overall shape of a
rotational landslide. The Altamira Landslide Complex is characterized by rolling hills with
numerous gullies and canyons oriented generally perpendicular to the shoreline. Landward, the
head of the ancient landslide is the prominent Valley View Graben, which sharply declines in
elevation by 145 feet into a relatively flat surface of approximately 400 feet in width.
The extension zone of the Altamira Landslide covers over 50 percent of the area and has a
stepwise series of scarps and platforms with the major scarp dropping from 1,200 feet msl to the
first head at 900 feet msl. The head scarp of the landslide contains some of the steepest
slopes, with between 150 percent and 280 percent gradient. The last “platforms” are at
approximately 500 feet msl, where there begins a relatively flat surface in the central portion of
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the ancient landslide, south of Narcissa Drive, that extends to the head of the Abalone Cove
Landslide.
The area of relatively flat terrain covers half a square mile in the central portion of the Altamira
Landslide Complex. This area is characterized by rolling hills with slope gradients generally
less than 60 percent. The Altamira Canyon cuts through this relatively gentle sloping surface
with elevations falling from 400 feet msl to approximately 250 feet msl over a distance of
100 feet. The Altamira Canyon is the longest canyon (8,800 feet) that extends from the crest of
the slide to the shoreline, just west of Inspiration Point.
Throughout the Altamira landslide there are a series of canyons that run parallel to each other
and range between 800 to 8,800 feet in length. From west to east there is the unnamed canyon
that bounds the landslide, as well as Vanderlip, Altamira, Kelvin, Portuguese, Ishibashi, Paint
Brush, and Klondike Canyons, with slope gradients that range between 100 percent and
280 percent.
Abalone Cove Landslide and the PBLC are generally within the compression zone or toe of
Altamira Canyon and are characterized by a hummocky topography with rounded hills and
some smooth valleys with a maximum elevation of 500 feet msl. On average, there is about
7 degrees dip in topography from the crest to the shoreline (Ehlig and Yen, 1997; Mackintosh,
1957). The crest of the PBLC is approximately 500 feet msl and the toe of the slide extends to
the shoreline. In this compression zone, PVDS runs generally east to west, parallel to the
shoreline. The elevation of PVDS ranges from approximately 160 to 220 feet msl and is about
800 feet from the shoreline.
Pronounced sea cliffs and narrow beaches are present at the shoreline. The most noticeable
features along the shoreline include two promontories that are present in the Western and
western Seaward subslide areas of the PBLC (Figure 3), the westerly Inspiration Point and the
easterly Portuguese Point with elevations up to 135 feet msl.
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3.2 Watershed Hydrology
A watershed is defined as a region or area bound peripherally by a divide and draining
ultimately to a particular watercourse or body of water. In this case, the bodies of water of
interest are the canyons that convey surface water, to one degree or another, through the area
of the PBLC. It is also of interest to characterize the areas from which stormwater drains and
ultimately runs off into the PBLC canyons. Water from those areas ultimately flows into the
PBLC canyons and, in turn, into the PBLC.
The PBLC receives water (both surface water and groundwater) from the watersheds of
Portuguese Canyon, Ishibashi Canyon, and Paintbrush Canyon. These canyons are generally
ephemeral, meaning that surface water does not flow through them throughout the year.
Rather, these canyons generally have flowing water when and after it rains and they convey
stormwater from the high ground in the watershed toward the Pacific Ocean. Collectively, they
are referred to herein as the PBLC Canyons. Klondike Canyon is considered herein separate
from the PBLC but, as described below, water from Klondike Canyon likely flows as underflow
across the watershed divide at the lower southwest end of the Klondike Canyon watershed.
Klondike Canyon is also an exception in that perennial water is observed flowing in the lower
reaches of Klondike Canyon. The PBLC Canyons are shown in Figure 5 with their collective
watershed boundaries.
The PBLC Canyons are located in what is identified as the “Ocean South South” (sic) drainage
area in the Master Plan of Drainage (MPD) (RBF Consulting, 2015), a part of the Santa Monica
Bay Watershed defined by the County of Los Angeles Department of Public Works. The PBLC
Canyons are directly tributary to the Pacific Ocean. The PBLC Canyons have storm drain
systems located in their upper reaches that discharge into the canyons that, in turn, drain
ultimately into the ocean. The area of the Portuguese Bend watershed that drains into the
PBLC Canyons is approximately 627 acres.
Over significant reaches of these canyons, notably the portions which direct water to and
through the PBLC, the drainage systems consist mostly of canyon bottoms that are unimproved
open channels. The surface of the ground within much of the PBLC is generally hummocky,
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irregular, and locally fissured due to the landslide activity. Previous drainage structures
constructed to control and convey stormwater runoff have failed. The MPD (RBF Consulting,
2015) found that the CMP structures were undersized for the calculated flow they would receive.
As a result, surface drainage within the landslide is generally poor and difficult to maintain.
Infiltration of the runoff conveyed through these canyons is a source of recharge for the
groundwater within the landslide (Ehlig and Yen, 1997).
As described in the MPD (RBF Consulting, 2015), Ocean South South has three major canyons:
Altamira Canyon, Portuguese Bend Canyon, and Paint Brush Canyon. While a part of the
delineated Ocean South South drainage area, surface water from Altamira Canyon does not
drain directly into PBLC like the other adjacent canyons and will not be discussed further herein.
Groundwater that originates from Altamira Canyon infiltration may, however, flow into the PBLC
area. Portuguese Canyon is located on the westerly side of the PBLC and generally forms the
boundary of two subslides termed by Ehlig and Yen (1997) as the West -Central and East-
Central slides. This boundary, and Portuguese Canyon, is defined by a near vertical fault that
extends in a north-south direction along the general alignment of Portuguese Canyon (Ehlig and
Yen, 1997). The upper reaches of Portuguese Canyon are steep and convey stormwater
quickly to the lower reaches where water moves more slowly in the low gradient terrain.
Smaller in size, Ishibashi Canyon, located east of Portuguese Canyon, drains into Paint Brush
Canyon which, in turn, drains into an undeveloped mountain-front alluvial fan area of the PBLC.
Paint Brush Canyon includes two debris basins in series upstream of the confluence of Ishibashi
and Paint Brush Canyons before discharging to the upper end of the PBLC, where evidence in
the field indicates that stormwater readily infiltrates.
Klondike Canyon is located east of Paintbrush Canyon and the PBLC. The area of the Klondike
Canyon W atershed is 680 acres and a smaller portion of that area drains into Klondike Canyon
itself. The southwest margin of the Klondike Canyon Watershed, where Klondike Canyon
stormwater empties into the Pacific Ocean, is within the mapped boundary of the PBLC.
Though it appears likely, based on its location relative to the PBLC boundary and the generally
low-lying surface terrain, it is unknown whether groundwater is moving from the lower Klondike
Canyon Watershed into the PBLC Watershed. This is a complicated area where the Klondike
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Canyon Watershed abuts the PBLC Watershed and the Klondike Canyon Landslide abuts the
PBLC in an area of maximum PBLC movement.
As mentioned above, there are several swales and storm drains that drain the upper reaches of
the watershed into the PBLC Canyons and Klondike Canyon where the water is then conveyed
to the Pacific Ocean (Figure 7). The upper watershed areas contributing to water flow into the
PBLC and Klondike Canyon landslides are located within the City of Rolling Hills. This may
represent legal and/or jurisdictional access challenges with respect to the implementation of
landslide abatement solutions that involve stormwater control and conveyance. Of the
combined approximately 1,300-acre area of the PBLC and Klondike watersheds, approximately
360 acres (28 percent) lies within Rolling Hills. The balance of the watershed areas (940 acres,
or 72 percent) lies within the City of Rancho Palos Verdes.
There are currently no known stream gage data based on monitoring of either dry weather or
storm water flow in the canyons that convey water into the PBLC and the Klondike Canyon
Landslide. These canyons have a bottom generally 10 to 20 feet wide and fall 15 to 20 feet in a
100-foot run. A hydrologic study for this area is not within the scope of this study. Based on
information in the MPD, it is estimated that the 100-year storm runoff for each of the above
canyons would be approximately 200 cubic feet per second (cfs). This is not a rigorously
derived design value, but rather an estimate to provide a basis to establish the rough sizing and
feasibility of improvements being considered as part of a conceptual landslide stabilization
solution.
3.3 Soils
The U.S. Department of Agriculture (USDA) SSURGO database (USDA, 2015) was used to
access information about the surficial soils at the PBLC (Appendix B). The SSURGO database
contains information about soil as collected by the Natural Resources Conservation Service
(NRCS) over the course of a century. The information is typically displayed in tables or as maps
and is available for most areas in the U.S. The information was gathered by walking over the
land and observing the soil. In many cases, soil samples were analyzed in laboratories. The
maps outline areas called map units. The map units describe soils and other components that
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have unique properties, interpretations, and productivity. The information was collected at
scales ranging from 1:12,000 to 1:63,360. More details were gathered at a scale of 1:12,000
than at a scale of 1:63,360. The mapping is intended for natural resource planning and
management by landowners, townships, and counties.
The soil survey information came from the Soil Survey of Los Angeles County, California,
Southeastern Part (CA 696), mapped at a scale of 1:24000, using aerial images dated May 25,
2010 to November 24, 2014.
The predominant soil unit symbol in the PBLC is 1168 with a mapping unit name of
Haploxerepts, 10 to 35 percent slopes. Rather than a typical association of soil series, the
name Haploxerepts refers to the soil taxonomic classification of surficial soils that predominantly
occur in the PBLC. Haploxerept soils typically occur at an elevation of 0 to 1,210 feet msl in an
annual precipitation zone that typically ranges from 13 to 17 inches. Mean annual temperature
typically ranges from 62 to 63 degrees Fahrenheit (°F). In this mapping unit, Haploxerept soils
make up about 90 percent of the landscape, with the minor component of 10 percent composed
of the Lunada soil that typically occurs on hillslopes.
Haploxerepts generally occur on landslides in mixed slide deposits derived mostly from
calcareous shale. The typical soil profile of a Haploxerept is as follows: 0 to 7 inches, loam; 7 to
20 inches loam with the incipient development of soil structure; 37 to 79 inches, channery loam.
A channery soil is a soil that is, by volume, more than 15 percent thin, flat fragments of
sandstone, shale, slate, limestone, or schist as much as 6 inches along the longest axis. A
loam is soil composed mostly of sand (particle size > 63 micrometers [µm]), silt (particle size >
2 µm), and a smaller amount of clay (particle size < 2 µm). By weight, its mineral composition is
about 40/40/20 percent concentration of sand/silt/clay, respectively. These proportions can vary
to a degree, however, and result in different types of loam soils: sandy loam, silty loam, clay
loam, sandy clay loam, silty clay loam, and loam, depending on which particle size
predominates.
Haploxerepts typically occur on slopes that range from 10 to 35 percent, are well drained
(internally), and have moderately high to high capacity to transmit water. Typical saturated
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hydraulic conductivities (Ksat) of Haploxerepts range from 0.60 to 2 inches per hour. Depth to
first water is typically greater than 80 inches.
Soils are also typically classified as lying within a hydrologic soil group that, when considered
with land use, management practices, and hydrologic conditions, determine a soil’s associated
runoff curve number. Runoff curve numbers are used to estimate direct runoff from rainfall
(NRCS, 2007). Soils were originally assigned to hydrologic soil groups based on measured
rainfall, runoff, and infiltrometer data. As the initial work was done to establish these groupings,
assignment of soils to hydrologic soil groups has been based on the judgment of soil scientists.
Assignments are made based on comparison of the characteristics of unclassified soil profiles
with profiles of soils already placed into hydrologic soil groups. Most of the groupings are based
on the premise that soils found within a climatic region that are similar in depth to a restrictive
layer or water table, transmission rate of water, texture, structure, and degree of swelling when
saturated, will have similar runoff responses.
The Haploxerepts mapped at the PBLC are classified as falling within the characteristic of
Hydrologic Group B (NRCS, 2017). Soils in this group have moderately low runoff potential
when saturated, and water transmission through the soil is not impeded. Group B soils typically
have between 10 percent and 20 percent clay and 50 percent to 90 percent sand and have
loamy sand or sandy loam textures (USDA, 2015).
Douglas (2013) also characterized PBLC area soils as commonly comprising soils that are
“expansive” in character. Douglas states that weathering and erosion of the Altamira bedrock
produced a soil that is rich in clay minerals with distinctive properties. These clays have the
ability to absorb and expel water so that they can swell (expand) or shrink (contract). When it
rains, the clays in the soil absorb water, expand and become sticky. In the summer, they dry
out and the clays lose water and contract. In the dry months, the soils in the area develop
cracks, sometimes more than an inch across and up to a foot deep. In the rainy months, the
cracks disappear as the clays absorb water. In the process of wetting and drying, expansion
and contraction, the soils on the slopes respond to gravity and slowly migrate downslope. This
is called soil creep. Expansive soils can also be a problem for slabs or foundations or anything
that is placed in or on the ground without proper footing. Expansive soil movement is related to
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rainfall patterns and can amount to tenths of an inch to inches per year (Douglas, 2013).
Douglas (2013) pointed out that in locations where GPS measurements indicate that land
displacement is minimal, there is the possibility that the slow movement is due to slope creep
from expansive soils.
In summary, surficial soils on the PBLC are generally loamy in texture with a proportion of sand,
silt, and clay of about 40/40/20 percent. They can take in and percolate water readily. They are
relatively deep and have a moderate to high water-holding capacity. They develop deep, wide
cracks during the dry summer and provide channels for later infiltration during the rainy season.
Once water has infiltrated and is stored in the soil profile, the presence of expansive clays
causes the soils to expand (or swell), closing the soil cracks. The cycle of expansion and
contraction is a source of soil creep. Without a pathway for surface water to runoff to the Pacific
Ocean, the infiltration of runoff water sourced from slopes higher on the PBLC readily occurs
and exceeds the storage capacity of surficial soils. The excess water then percolates into
underlying formations, beyond the reach of transpiring plants, where it potentially provides a
mechanism to facilitate more significant slide movements.
3.4 Geology
The PBLC is located on the northwest trending Palos Verdes Peninsula, which is formed on the
hanging wall of the southwest-dipping Palos Verdes fault (Douglas, 2013) (Figure 8). The
Peninsula is the result of uplift and formation of a doubly plunging anticline. The anticline plays
an important role in the presence of the PBLC, which is located on the southern flank of the fold.
The head of the landslide coincides with the crest of the anticline and the south limb is gently
inclined in the seaward direction. The sedimentary rocks that form the Peninsula include the
Mesozoic Catalina Schist, Monterey Formation, marine terrace deposits, alluvium, and landslide
deposits.
The oldest rocks of the Peninsula consist of Mesozoic Catalina Schist, which forms the core of
the anticline (Ehlig, 1992). Middle to Late Miocene marine sediments of the Monterey
Formation unconformably overlie the schist, and these sediments were deposited in an ocean
basin (Douglas, 2013). Widespread volcanism occurred in the early phase of deposition of the
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Monterey Formation, which contributed volcaniclastic sediments to the Monterey Formation
(Conrad and Ehlig, 1987). Conrad and Ehlig (1987) subdivided the rocks of the Monterey
Formation into three main members, from lower to upper: the Altamira Shale, Valmonte
Diatomite, and Malaga Mudstone (Figure 9). In the Pliocene, the ocean basin was
subsequently folded into an anticline and uplifted what is now the Peninsula, producing an
island separated from the mainland by a shallow sea (Douglas, 2013). Erosion of the uplifted
island resulted in sedimentation of the shallow sea, forming a peninsula connected to the
mainland. Fluctuations of sea levels in the Pleistocene simultaneous with uplift resulted in
preservation of 13 marine terraces that circumscribe the Peninsula. Modern day sea level
produces near vertical sea cliffs almost 150 feet high and erodes the landslide toe at relatively
high rates.
The two upper members of the Monterey Formation are mostly composed of biogenic materials
such as diatomite, diatom-rich shale, and phosphate-rich mudstones. The Altamira Shale
member is further subdivided into lower and middle tuffaceous shale and upper cherty and
phosphatic lithofacies (Figure 9) (Douglas, 2013). The tuffaceous shale is rich in volcanic ash
that contains interbeds of clay and bentonite that are inherently weak. The bentonite beds are
the slip surfaces of most landslides in the peninsula (Ehlig, 1992; Douglas, 2013). The clay and
bentonite interbeds form aquitards or aquicludes that permit the buildup of pore water pressure.
Outcrops of the tuffaceous lithofacies in the ancient Altamira Landslide Complex are
predominantly composed of tuffaceous shales with interbeds of cherts, silty sandstone, and
intrusive basalt sills (Douglas, 2013).
The Altamira Shale member also contains beds of tuff turbidite, ash fall, and debris flow tuffs
that vary in thickness and are discontinuous over short distances (Douglas, 2013). Two
distinctive tuff units occur within the tuffaceous lithofacies including the Miraleste Tuff and the
Portuguese Tuff (Douglas, 2013). The Miraleste tuff is positioned in the upper part of the facies
and the Portuguese tuff occurs approximately 450 feet below the top of the tuffaceous facies.
The Portuguese Tuff ranges in thickness from approximately 20 to 60 feet with an average
thickness of approximately 50 to 60 feet in the PBLC (Leighton and Associates, 2000). The
variable thickness is the result of deposition on a hummocky sea floor interpreted to be caused
by a single eruptive event (Ehlig, 1992). Most of the tuff has been converted to montmorillonite
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clay (bentonite) due to groundwater and heat (Douglas, 2013). The Portuguese Tuff functions
as a zone of low shear strength and as an aquiclude in the PBLC (Ehlig, 1992). In the upper
and middle portions of the PBLC, the landslide shear zone is positioned in a range
approximately 50 feet above the tuff to coinciding with the top of the tuff. In the lower portion of
the PBLC, the shear zone is positioned near the base of the tuff (Ehlig, 1992).
Several folds and faults occur in the PBLC and offshore areas, the largest of which are anticlinal
folds (Figure 10). All of the folds are asymmetric, east-west trending, and anticlinal. None of
the onshore folds are exposed at the surface but are identified with subsurface data. The folds
are significant in that they have influenced the direction of movement of the subslides of the
PBLC (Douglas, 2013). Ehlig and Yen (1997) described the western edge of the east central
subslide to be defined by a near vertical fault which extends in a north-south direction along the
general alignment of Portuguese Canyon. The canyon probably developed along the fault. The
fault is controlled by a discontinuity in the underlying bedrock structure.
All of the geologic structures were formed during uplift and folding of the Peninsula. The crests
of the anticline located at the head of the PBLC trends westward to Altamira Canyon where it
underlies the hills of “Peacock Flats.” This anticline retards seaward movement of the ancient
Altamira Landslide. Subsurface data reveal two flexural faults in the bedrock under the PBLC
that trend west to east (Douglas, 2013). One of the flexures coincides with the boundary of the
eastern and inland subslides (Figure 3). These flexures cause undulations in the slip zone of
the PBLC, which creates large tension cracks in the slide mass as it moves over them.
3.5 Landslide Characterization
The PBLC is the reactivated portion of a bowl-shaped area that encompasses approximately
2 square miles on the Palos Verdes Peninsula in the Ancient Altamira Landslide Complex
(Figure 3). The Ancient Altamira Landslide Complex was first mapped by Woodring et al.
(1946). More recent studies have moved the head of the landslide northward to include the
Valley View graben (Douglas, 2013). There are differing hypotheses that postulate on the
initiation and evolution of the Ancient Altamira Landslide Complex. Jahns and Vonder Linden
(1972) believed that the Ancient Altamira Landslide Complex was the result of a series of semi-
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independent slides that formed in three separate time intervals during the 500,000 years. The
oldest slides are located inland and the slides became progressively younger toward the coast.
Ehlig (1992) proposed that the Ancient Altamira Landslide Complex initiated as a megaslide that
moved as a simple translational glide block unit and, with continued displacement, the original
slide block became fragmented. Furthermore, he concluded that the megaslide occurred
sometime prior to 125,000 years ago and was no older than 200,000 years ago. Douglas
(2013) argued that the AALC contains terrace remnants that are older than 200,000 years and
therefore, its origin is older. He proposed that the upper block of landslide complex separated
from a paleo sea cliff dated at 780,000 years and initial movement began shortly after this date.
Douglas (2013) also believes that movement occurred in episodes with the oldest block at the
head and the youngest at the coast which is consistent with the Jahns and Vonder Linden
(1972) model. Given that borings drilled through the PBLC have determined that the ancient
rupture surface is mostly at or the near the top of the Portuguese Tuff and the rupture surface is
stratigraphically continuous, Leighton and Associates (2000) favor initial translational movement
as a single sheet that subsequently broke up into large blocks consistent with the Ehlig (1992)
model.
The active PBLC encompasses approximately 250 acres with a maximum width of 3,600 feet
and maximum head-to-toe length of approximately 4,200 feet (Douglas, 2013). The PBLC,
together with the Abalone Cove and Klondike Canyon Landslides are reactivated portions of the
Ancient Altamira Landslide Complex (Ehlig, 1992; Douglas, 2013). The western margin of the
PBLC is poorly defined and transitory with respect to the Abalone Cove Landslide, whereas the
east margin is well-defined. The internal structure of the landslide is established to be a series
of randomly oriented large blocks separated by fractures and grabens (Ehlig and Yen, 1997;
Leighton and Associates, 2000). Five large, semi-independent blocks or subslides were
identified by Ehlig (1992), including the Landward, East-Central, West-Central, and Seaward
subslides (Figure 3).
The Abalone Cove Landslide Abatement District (ACLAD) is the first Geologic Hazard
Abatement District (GHAD) created (in 1981) under the Beverly Act of 1979 (SB1195). The
ACLAD is governed by a board of directors elected from property owners in the district area and
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assesses property owners to pay for the construction and maintenance of abatement measures
in the Abalone Cove Landslide area, such as groundwater dewatering wells. The ACLAD
maintains an extensive dewatering well network in the area. The well network has reportedly
lowered water levels in the slide area up to a maximum of approximately 60 feet (Douglas,
2007) and helped to promote overall relative land stability in the ACLAD area.
Ehlig and Yen (1997) supplemented their subsurface exploration data set with data acquired
from previously drilled borings to construct a structure contour map of the basal rupture surface
in the PBLC. The contour map estimates and maps the elevation of the rupture surface for the
Landward, West-Central, and Seaward subslides. However, lack of subsurface data (data gap)
east of Portuguese Canyon permits only inferred mapping of the rupture surface in this area.
The undulating shape of the rupture surface is controlled by the structure of the underlying
bedrock. The dips of the rupture surface range from approximately 15 to 25 degrees beneath
the Landward subslide and flatten to less than 5 degrees in an anticlinal undulation along the
southern margin near the West-Central and East-Central subslide boundaries (Ehlig and Yen,
1997; Leighton and Associates, 2000).
One significant characteristic of the basal rupture surface is the trough shaped basin formed
along the eastern part of the East-Central subslide (Appendix C). The rupture surface steepens
to 17 degrees at the northern flank of the trough with the central portion of the trough positioned
just below sea level. The southern flank of the trough is gently inclined to the north and the
rupture surface rises back up above sea level. Ehlig and Yen (1997) reported that a near
vertical, north-south tear fault forms the boundary between the West-Central and East-Central
subslides. The rupture surface of the West-Central subslide is generally uniformly gently
dipping at approximately 7 degrees. An anticlinal undulation produces a 30 to 40 foot rise in the
rupture surface which produces a buttressing effect on the subslide as the mass must climb to
reach the crest of the fold (Leighton and Associates, 2000). The rupture surface of the Seaward
subslide generally dips 5 degrees seaward and accommodates rotation of the slide blocks as
wave erosion removes the toe of the active PBLC.
Geologic cross-sections presented by Ehlig and Yen (1997) show that the topography (as of
1995) was nearly parallel to the underlying active rupture surface. The sections indicate that the
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thickness of the landslide mass is relatively uniform and averages approximately 100 feet above
the rupture surface. However, Douglas (2013) states that, in places, the landslide complex is
over 200 feet thick. Ehlig and Yen (1997) estimated that the total volume of PBLC mass is
approximately 40 million cubic yards. Subsurface data indicate that the rupture surface is
underlain by bedrock east of Portuguese Canyon and Ancient Altamira Landslide Complex
debris west of Portuguese Canyon (Leighton and Associates, 2000). As a result, there are
deeper slide and multiple slide planes present beneath the subslides located west of
Portuguese Canyon, which coincides with the West-Central and East-Central boundary.
Borings drilled by Ehlig and Yen, 1997 indicate that the Portuguese Tuff is at depth beneath the
rupture surface throughout the northern portion of the PBLC. The portion of strata that are
positioned between the rupture surface and the underlying Portuguese Tuff consists of relatively
stronger strata derived from Catalina Schist debris and siliceous biogenic material. The rupture
surface occurs along a sheared bentonite bed approximately 30 to 40 feet above the top of the
Portuguese Tuff in the PBLC except for the northernmost portion and at the coast (Ehlig and
Yen, 1997). The clay material of the rupture surface consists of both calcium-rich and sodium-
rich montmorillonite clay (Ehlig and Yen, 1997; Leighton and Associates, 2000). The sodium-
rich clay holds more water and is weaker than clay calcium-rich clay. Due to this fact, Ehlig and
Yen (1997) proposed a lime injection program to increase the amount of calcium cations in the
clay, which would strengthen the rupture surface clay. However, Leighton and Associates
(2000) determined that the rupture surface consists of a substantial amount of calcium-rich clay
and the lime injection may not yield desired stabilization results.
3.6 Hydrogeology
Studies of the PBLC have consistently concluded that water moving in the subsurface is a
significant contributing factor to the PBLC landslide instability. Subsurface water exists in the
pores of soils and unconsolidated sediments and in fractures that exist in both unconsolidated
sediments and hard rock. When water does not completely fill the pores that exist in soils, the
moisture condition is referred to as “unsaturated.” The balance of the pore space is filled with
soil vapor, which is typically in communication with the surface. When water completely fills the
pores spaces, the moisture condition is termed “saturated.” Like any other free water surface
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(such as a pond or lake surface), a water table surface has a pore pressure, or static head, of
zero. The water pressure increases linearly with depth below the water table. Water pressure
can also build up as groundwater rises and encounters an overlying low-permeability zone that
“confines” the groundwater. In this case, water in a drilled borehole would rise up above the
level at which it was first encountered. If the water rose sufficiently high enough to encounter
the surface, the water pressure would be termed “artesian.”
Subsurface water includes water in soils that exists under conditions less than saturation above
a water table and water that exists under saturated conditions below a water table or below a
confining layer. Subsurface water is part of the continuous circulation of water between the
ocean, atmosphere, and land called the hydrologic cycle.
3.6.1 Groundwater Recharge
At the PBLC, water enters the subsurface by:
• Direct precipitation and infiltration through soils
• Drainage of surface water from locations upslope and subsequent infiltration and
percolation
• Percolation of water from private residential on-site wastewater treatment systems such
as septic systems
• Groundwater flow from upgradient locations, termed “underflow”
A preliminary groundwater balance was developed for a golf course project proposed for an
area in the east-southeastern PBLC (Leighton and Associates, 1998). The information available
to support this analysis was limited but deemed sufficient to provide a first order approximation
of the amount of water entering and leaving the proposed project site (the golf course project
was never completed).
Rainfall data from the Los Angeles County Fire Station at the top of the watershed on Crest
Road were used for the water balance calculations. Based on historical precipitation data for
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the years 1947 to 1996, the average annual rainfall at the station was estimated to be
14.1 inches. This represents the amount of water (after deductions for the amounts that runoff,
evaporate, or transpire from plants) that can potentially infiltrate and percolate into the
subsurface of the PBLC. The area of the PBLC watershed is approximately 620 acres
(Section 6.2) (Figure 5). The resulting volume of water that falls on the PBLC watershed in an
average year is approximately 728 acre-feet of water (1.175 feet x 620 acres), the equivalent of
about 234 million gallons of water.
As calculated from the estimates presented in Leighton and Associates (1998), approximately
10 percent of the rain that fell on their proposed project area in an average rainfall year
recharges and becomes groundwater. Extrapolating that percentage to the case of the PBLC
area results in approximately 71.8 acre-feet, or 23.4 million gallons, of recharge. In addition,
Leighton and Associates (1998) also determined for their proposed project site that the average
annual rainfall of the 10 wettest years was 26.3 inches. In the 10 wettest years, Leighton and
Associates (1998) calculated that approximately 29 percent of the rain that fell recharged and
became groundwater. Using a wet-year rainfall of 26.3 inches for the PBLC, the recharge to
groundwater that results on the PBLC watershed area would be about 388 acre-feet, or
127 million gallons. These recharge estimates do not separate the rainfall water that infiltrates
and percolates directly from water that runs off from upgradient locations and subsequently
infiltrates and percolates into the Red Zone of the PBLC. Rather, these values represent
estimates of the recharge that occurs over the entire watershed. These recharge values are
likely conservative, and a more detailed analysis would likely reveal that the percentage of
rainfall that results in recharge is higher than estimated by Leighton and Associates. This is
because an important limitation of the method used by Leighton and Associates (1998) is the
assumption that rainfall stored within the soil is subject to evapotranspiration until the soil
moisture capacity is exceeded. However, existing conditions at Portuguese Bend include
desiccation cracks, fractures, and fissures caused by landslide movement that may permit water
to migrate beyond the depth of evapotranspiration before the soil reaches its moisture capacity.
This limitation in the method may result in an underestimate of groundwater recharge.
Leighton and Associates (1998) also estimated the contribution to groundwater recharge by
septic systems based on (1) the presence of 80 homes upslope of the project, (2) an estimated
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annual indoor consumption of 1,350 cubic feet of water per month, and (3) the assumption that
all indoor water flowed to the septic system. The resulting contribution to subsurface water by
percolation from private septic systems was estimated to be about 30 acre-feet per year. Based
on the estimates for total project area recharge presented by Leighton and Associates (1998),
septic tanks contribute about 30 percent of the total groundwater recharge in dry years, and
about 7.2 percent of the total groundwater recharge in the 10 wettest years. While additional
study of the PBLC groundwater budget is merited to clarify the water budgets of both shallow
and deep groundwater, the preliminary water budget work suggests that there is a substantial
amount of recharge into the PBLC, particularly in wet years, and that groundwater recharge
from septic tanks can be significant in dry to average water years.
During periods of heavy rainfall, large quantities of runoff flow onto the landslide from the
tributary canyons. Field observation indicates that, although the water from these canyons was
conveyed across the landslide through a combination of natural and improved drainage
courses, it appears that significant sections of corrugated metal pipe (CMP) used for surface
drainage are broken and inoperable and that significant quantities of runoff infiltrate and
percolate into the ground within and around the periphery of the PBLC. Douglas (2013) stated
that “In Portuguese and Paint Brush Canyons, the lower reaches of the canyons have been
destroyed and 100 percent of the storm water from these canyon flows directly into the head of
the Portuguese Bend landslide.” Our field observations are consistent with this statement.
Leighton and Associates (1998) estimated the amount of recharge contributed by irrigation.
Because the northern border of their project area was at the upper end of the watershed, it
represented a no flow groundwater (and surface water) boundary in their analysis. In other
words, no water flowed south into the area from north of the boundary. As a result, all
groundwater flowing south into their proposed project site was the result of groundwater
recharge from areas between the north end of the study area (and watershed) and the project
site itself. The same is true for the PBLC. All groundwater inflow into the PBLC results from
recharge occurring upslope. Leighton and Associates (1998) estimated that up to 77 acre-feet
per year could be entering their project area from upslope irrigation recharge. Extrapolated to
the PBLC, and similar to septic tanks, irrigation return flow represents a significant source of
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groundwater recharge to the PBLC. This component of recharge should be investigated further
in a water balance study developed to support the final design of a land stabilization solution.
3.6.2 Groundwater Occurrence
Groundwater generally occurs in two water-bearing zones at the Site. “Shallow” groundwater
typically flows above the bentonite layers (shear zones) that form the main slip or rupture zones
(failure surfaces) and is fed by general recharge, preferential recharge through local fractures,
recharge through the canyon bottoms, and recharge that occurs where the canyons dump storm
water onto alluvial fans, head slopes, sag ponds, and hummocky areas of the slide area.
Douglas (2013) reported that wells pumping from this layer respond quickly (days to weeks) to
major rain storms. A second water-bearing zone consisting of “deep” groundwater originates in
the upper part of the drainage basin and is largely confined to below the rupture zones. This
deep groundwater is confined and groundwater builds up pressure over time. Douglas (2013)
also reported that wells drilled deep enough often encounter pressurized groundwater zones
below the basal rupture surface.
Leighton and Associates (1998) reported that unconfined groundwater of the shallow water-
bearing zone occurs across the Site, and that it has historically been observed at depths
ranging from approximately 5 to 15 feet below ground surface (bgs), at monitoring wells PBS-7,
B88-4, and B96-12, to approximately 90 to 110 feet bgs, at monitoring wells PBS-2, PBS-3, C-4,
C-5, and C-6. In general, the shallowest occurrences of groundwater have been observed in
the Landward subslide, above the heads of the East-Central and West-Central subslides. The
deepest occurrences of groundwater have been observed north of the active landslide area
(monitoring wells C-4 through C-6), and underlying the north-south trending topographic ridge
where monitoring wells PBS-2 through PBS-4 are located.
The horizontal hydraulic gradient of the unconfined groundwater of the shallow water-bearing
zone trends north to south and has a magnitude of approximately 0.10 foot of vertical head loss
per horizontal foot (Leighton and Associates, 1998), similar to the general site topographic
gradient. Experience indicates that, in general, horizontal groundwater hydraulic gradients
typically range from 0.01 to 0.00001. By comparison, the gradient at the PBLC is therefore
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unusually high. High horizontal hydraulic gradients can be indicative of low-permeability
conditions, areas of intensive groundwater recharge, high topographic relief, and/or
groundwater extraction. Under homogeneous conditions, the direction of groundwater flow is
generally parallel to the direction of the hydraulic gradient, in this case north to south.
Appendix C shows the contoured piezometric surface of the water table at the site based on
interpolation of groundwater elevations measured in wells at the site.
The occurrence of groundwater in the deep water-bearing zone beneath the rupture zone is less
well understood and additional characterization of site deep groundwater is needed to facilitate
a clear understanding of the hydraulic forces that deep groundwater is exerting on PBLC land
stability. Ehlig and Yen (1997) reported that nested piezometers have been completed on the
PBLC at four locations, and that at each location pneumatic pressure transducer readings
indicate that groundwater occurs below the slide plane. Ehlig and Yen (1997) also reported that
vertical hydraulic head measurements indicate that a downward vertical gradient occurs within
the landslide mass and an even greater downward vertical gradient exists across the slide
plane. The presence of these downward vertical gradients at the lower end of the hillslope was
potentially attributed to increased groundwater recharge rates along the landscape of the
landslide, including the presence of extensional ground fractures.
Ehlig (1992) (as cited in Ehlig and Yen, 1997) reported on a well that was constructed and
screened at the toe of the Klondike Canyon landslide and yielded artesian groundwater flow.
The interpretation was given that slope stability analyses pertaining to the Seaward subslide
need to consider that confined groundwater conditions occur beneath the slide plane.
Ehlig and Yen (1997) generally concluded that groundwater occurrence beneath the site slide
rupture plane was consistent with groundwater recharge occurring at the upper end of the hill
slope and subsequent deeper migration beneath the slide plane towards the ocean.
Groundwater occurrence at the regional scale is shown in Appendix C. Crest Road located
north of the PBLC is approximately located at the topographic crest of the hill and is the
approximate location of the surface water and groundwater flow divide. Surface water and
groundwater that occurs north of Crest Road generally flows inland towards the Pacific Coast
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Highway. Surface water and groundwater that occurs south of Crest Road generally flows
southward, through the PBLC, and toward the Pacific Ocean. Surface water that falls or flows
south of Crest Road has the opportunity to infiltrate and percolate into the subsurface of the
PBLC and become groundwater. This is the water that is the focus of concern regarding PBLC
land stability.
Leighton and Associates (2000) present a detailed cross-sectional view (UU-UU’) that traverses
through the main body of the PBLC from the upland area where the scarp of the slide headwall
is located to the Pacific Ocean. The relationship is shown between the existing surface
topography (existing grade), the interpreted water table (indicated by inverse triangles), and the
interpreted recent below-grade active failure surface of the PBLC, as interpreted in 1999. As
depicted, the water table surface is located above the interpreted active failure surface with a
gradient that roughly mimics the gradient of the surface topography. The area of greatest
thickness of the saturated zone within the PBLC was reported to be located inland (north) of
PVDS. The maximum interpreted saturated zone thickness is approximately 90 feet, and the
top of the saturated zone, at the point of maximum saturated zone thickness, was reported to be
located about 100 feet bgs (Leighton and Associates, 2000). Though additional work needs to
be accomplished to evaluate and delineate the specific occurrence of groundwater in the PBLC,
the previous work done to evaluate the occurrence of groundwater in the PBLC provides the
conceptual basis to evaluate and select technologies that can be used to stabilize land
movement.
3.6.3 Water Wells
Limited documented information is available on the number, construction details, and spatial
distribution of the water wells in the PBLC. Information provided by the City of Rancho Palos
Verdes indicates that up to 20 water wells have been constructed and installed within the PBLC.
Except for four recent wells installed in 2016, no information could be located which documents
the well construction details, last surveyed location, purpose of well (monitoring or dewatering),
date of installation, well temporal monitoring data, or the current status of the well. That
limitation represents a significant data gap that should be aggressively addressed moving
forward. A map of currently known extraction well locations is presented as Figure 11.
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A well inspection survey should be conducted, including well soundings and video survey where
necessary, in order to construct one consolidated, comprehensive database of site water well
information and to provide the basis to initiate a monitoring program moving forward. An
assessment should be prepared of the adequacy of the well network for spatial and temporal
monitoring of groundwater within the PBLC. Based on that assessment, the monitoring well
network should be augmented and a monitoring program initiated and maintained to provide
data that will guide and evaluate the performance of the selected program to stabilize the PBLC.
Regular, periodic well inspection surveys are also recommended to evaluate the impact of land
movement on the monitoring network and the need for monitoring network maintenance.
Ehlig and Yen (1997) report that groundwater elevations in the East-Central subslide area are
thought to have risen about 50 feet between the slide activation in 1956 and 1968. They
attributed the rise in groundwater elevations to an increase in the rate of groundwater recharge
within the landslide area caused by the disruption of drainage patterns and the opening of
fissures and cracks following the 1956 onset of movement. Water well elevation data presented
for four PBLC wells with close correlation of groundwater elevation increases to high rainfall
months indicate that groundwater recharge is occurring within a month of high rainfall events. In
other wells, particularly one located in the East-Central subslide area, the lag between rainfall
occurrence and water elevation response was longer, up to 5 months.
Changes in groundwater elevation with time and in relation to rainfall events vary depending
upon the well (Leighton and Associates, 2000). This suggests that multiple processes are
involved in the delivery and removal of groundwater from the site and highlights the need to
institute and formalize a monitoring program with the ability to record short and long term cyclic
events. Such a formalized monitoring program and the resulting database would facilitate the
collection, storage, and data interpretation critical to developing a detailed comprehensive
understanding of the mechanisms which control the stability of the PBLC.
3.7 Geotechnical Modeling
Slope stability evaluations of the PBLC have been performed in the past in support of
development of various remedial measures (e.g., Ehlig and Yen, 1997; Leighton, 2000). Past
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studies, however, were subject to significant limitations. For example, prior models of the PBLC
were two-dimensional cross sections and hence could not capture the true three-dimensional
nature of the PBLC. Stability evaluations could not replicate the observed conditions. Attempts
were made to back-calculate shear strength parameters, but different results were obtained for
each two-dimensional cross section evaluated, further impeding development of viable remedial
measures.
Recently (over the past five years), significant advances have been made in three-dimensional
modeling of slope stability. It is now possible to develop a three-dimensional stability model of a
multi-acre site such as the PBLC based upon three-dimensional surfaces rather than two-
dimensional cross sections. Review of available studies as discussed Sections 2 and 3
indicates that, with reasonable data processing, available information is suitable and sufficient to
develop a preliminary 3D stability model of the PBLC using the following surfaces:
• Ground surface (topography)
• Groundwater elevation surface
• Basal shear plane surface
The ground surface topography of the PBLC was provided by the City (Section 2). The
groundwater surface map produced by Ehlig and Yen (1997) was selected as the most
comprehensive and representative for the modeling effort. Groundwater elevations were
laterally extrapolated to the perimeter of the model area (approximately 10 percent of the lateral
model area) based on the mapped water level data measured within the PBLC area. The 1997
basal rupture surface map also from Ehlig and Yen (1997) was selected as the most appropriate
basal shear plane map for the modeling effort. Basal rupture surface elevations were also
laterally extrapolated (approximately 10 percent of the lateral model area) based on mapped
data measured within the PBLC area.
An image of the preliminary three-dimensional stability model of the PBLC is shown in Figure
12. This model image was generated using SVSlope from SoilVision, Inc.
(https://www.soilvision.com/), which is the latest generation three-dimensional slope stability
evaluation program. Additional imagery from the modeling effort is provided in Appendix C,
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including the approximate mapped limits of landsliding, several lateral cross-sections (A-A’ to
I-I’), and one transverse cross-section (1-1’). These images show that groundwater occurs
above the basal rupture surface within the PBLC. DBS&A performed the following preliminary
evaluations using the model software:
• Back-analysis of the PBLC
• Forward-analysis of the PBLC
The back-analysis was performed to estimate shear strength parameters along the basal failure
surface. Cohesion was set to zero, while friction angle was iterated until the calculated FOS
reached 1 (unity), which corresponds to the incipient failure of the landslide complex. An FOS
greater than 1.0 theoretically corresponds to the cessation of landsliding. Each model iteration
consumed approximately 3 hours of computational time. Back-analysis modeling indicates the
following:
• Back-calculated friction angle equals 6.7 degrees, which is within the range of values
reported in prior laboratory testing (Leighton, 2000).
• The direction of sliding (roughly north to south) is consistent with observations.
• The shape of the failure surface based on model calculations is consistent with
observations and interpretations (i.e., Ehlig and Yen, 1997).
Forward-analysis was performed to evaluate the effect of groundwater elevation on the stability
of the PBLC. The results indicate a strong correlation in which the FOS increases with a
corresponding decrease in groundwater elevation (Figure 13):
• An elevation decline of 5 feet results in an increase in the FOS of approximately
3 percent (FOS increases from 1 to 1.03).
• An elevation decline of 40 feet results in an increase in the FOS of approximately
13 percent (FOS increases from 1 to 1.13).
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Model limitations include the following:
• The 1997 groundwater elevation map may not be representative of current conditions; it
especially may not be representative of rainy periods that precede accelerated
landsliding.
• The steady-state seepage option within the three-dimensional stability model was not
used due to the lack of data and their interpretation.
• It was assumed that groundwater elevation (i.e., surface) is not affected by artesian
pressures, although there is historical evidence that the basal failure surface may be
subject to artesian pressure (Douglas, 2013).
• As noted above, the 1997 groundwater and basal failure surfaces were laterally
extended by extrapolation of existing data. Both groundwater elevation contour maps
and contour maps of the basal rupture surface can be improved and refined based upon
the results of supplemental investigation and data interpretation.
• The elevation of the groundwater surface that will exist upon implementation of proposed
remedial measures (Section 4.6) is not known at this point.
Importantly, the preliminary three-dimensional slope modeling confirms that a reasonable
reduction in the elevation of the groundwater surface (i.e., 10 to 20 feet) could result in a
significant reduction in land movement in the PBLC area (an increase in FOS up to
approximately 8 percent) (Figure 13).
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4. Feasibility Study
The FS presented below consists of the following sections:
• ARARs
• Remedial Action Objective
• General Response Actions
• Identification and Screening of Technology Alternatives
• Detailed Analysis of Remedial Technologies
• Preferred Alternative
4.1 ARARs
In accordance with the CERCLA-analogous process for selecting an appropriate remedy being
implemented in this document, remedial actions must meet the requirements of relevant federal
environmental laws or more stringent state environmental laws referred to as ARARs. Remedial
alternative screening must include ARARs evaluation.
4.1.1 Definitions
As defined previously, ARARs is an acronym for Applicable or Relevant and Appropriate
Requirements. Applicable requirements are those “cleanup standards, standards of control,
and other substantive requirements, criteria, or limitations promulgated under federal
environmental or state environmental or facility siting laws that specifically address a hazardous
substance, pollutant, contaminant, remedial action, location, or other circumstance. Only those
state standards that are identified by a state in a timely manner and that are more stringent than
federal requirements may be applicable” (CFR 300.5).
If a requirement is not applicable, it still may be relevant and appropriate and address issues at
the site such that their use is well suited to the particular site (U.S. EPA, 1991b). As
summarized by U.S. EPA, environmental laws and regulations can in part be broadly classified
into three categories:
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• Laws and regulations that restrict activities at a given location
• Laws and regulations that control specific actions
There are therefore two types of ARARs:
• Location-Specific ARARs: Intended to protect unique or sensitive areas, such as
wetlands, riparian areas, historic places, and fragile ecosystems, and restrict or prohibit
activities that are potentially harmful to such areas.
• Action-Specific ARARs: Activity or technology based. These ARARs control remedial
activities involving the design or use of certain equipment or technology or regulate
discrete actions and are used in remedial technology alternatives screening.
To-be-considered criteria (TBCs) are also identified in addition to ARARs. TBCs are advisories,
guidance, policies, and/or proposed regulations or standards that might be applicable or
applicable in the future. Finally, local permitting requirements and ordinances are also
applicable when performing remedial actions.
4.1.2 Identified ARARs
ARARs are summarized in Table 1 and include:
1. 1961 California Lake and Streambed Alteration Program
2. 1968 California Anti-degradation Policy
3. 1969 California Porter-Cologne Act
4. 1970 California Environmental Quality Act (CEQA)
5. 1970 California Endangered Species Act (CESA)
6. 1972 Federal Clean Water Act (CWA)
7. 1973 Federal Endangered Species Act (ESA)
8. 1973 USFWS Habitat Conservation Plans
9. 1993 USEPA Non-point Pollution (NPS) Management Guidance
10. 1995 SWRCB Water Quality Policy, Enclosed Bays and Estuaries
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11. 1998 California Coastal Zone Management Act
12. 2002 SWRCB Lake and Streambed Alteration Program 1602
13. 2004 SWRCB Water Quality Enforcement Policy, Enclosed Bays and Estuaries
14. 2007 RWQCB Los Angeles Basin Plan
15. 2011 California NPS Pollution Control Policy
16. 2011 SWRCB NPDES Program
17. 2015 SWRCB 303(d) Listing Policy of 2004, amended 2015
18. 2015 California Division of Occupational Safety and Health regulations (Cal-OSHA)
19. 2015 SWRCB/RWQCB 401 Water Quality Certifications and Wetlands Program
20. 2017 City of Rancho Palos Verdes Grading permit program
21. 1991 Natural Communities Conservation Plan (NCCP) (draft)
4.2 Remedial Action Objective
As discussed in Section 1.3, the specific purpose of this FS is to identify viable conceptual
solution options for the City’s consideration that will accomplish the following overall project
goals:
• Provide the geotechnical conditions that reduce the risk of damage to public and private
property and would allow for the significant improvement of roadway infrastructure,
safety, and stability.
• Significantly reduce human health risk and improve safety in the City.
• Significantly reduce sediment deposition into the Pacific Ocean that is causing
unacceptable turbidity in the coastal and marine environment.
• Select remedy options that will be consistent with the City’s NCCP/HCP, specifically
Section 4.1.2.
Remedial action objectives (RAOs) as defined by CERCLA and adapted for this FS are one or
more defined, specific project end-points or specific goals. The single RAO defined for the
Project Area is as follows:
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• RAO1: Significantly reduce project area land movement
The project area is defined as the southeastern PBLC area (Red Zone) where land movement
has consistently been measured at the greatest rate. A significant reduction in land movement
in the project area would address each overall project goal. Infrastructure operation and
maintenance, including repair, redesign, and stabilization of PVDS, could be conducted with a
more regular, less frequent, and more cost-effective schedule. A stabilized roadway would
clearly be much safer for motorists and ensure the expedited transit of emergency vehicles as
necessary.
Infrastructure in the project area could also be upgraded, including sewer, water, and electrical
lines, with significantly reduced land movement. Once land movement is significantly reduced,
the coastal shore cliff would no longer be regularly driven into the surf zone by ongoing mass
movement upslope; thus, sediment turbidity in the coastal and marine environmental would be
decreased. In addition, the proposed remedy will stabilize the land within the City’s Palos
Verdes Nature Preserve. Further, remedy options will be identified consistent with the
NCCP/HCP.
4.3 General Response Actions
General response actions (GRAs) as defined by CERCLA and adapted for this FS describe
broad, general categories of technologies that will satisfy the RAO and provide a framework for
identifying specific remedial technologies for screening and detailed analysis. The GRAs
identified to address the RAO are:
• Subsurface dewatering
• Stormwater control
• Engineered slope stabilization measures
• Eliminate septic system discharge
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4.3.1 Subsurface Dewatering
Preventing new water from entering the PBLC can be achieved by stormwater control and
extracting existing groundwater in the subsurface as much as possible to reduce soil saturation
and reduce continued landslide movement. Preliminary three-dimensional slope modeling
confirms that a reasonable reduction in the elevation of the groundwater surface of 5 to
15 percent would result in a significant reduction in land movement in the PBLC area
(Section 3.7). Subsurface dewatering through groundwater extraction should be conducted
where surface water infiltration and groundwater recharge has historically had the greatest
impact, such as in the head scarp area, the project area perimeter, and/or within the interior of
the project area. Groundwater extraction could be coupled with regional stormwater capture as
discussed below to optimize the effectiveness of the overall subsurface dewatering effort.
Subsurface dewatering is typically conducted with either or both horizontal and vertical
groundwater extraction wells. Horizontal groundwater extraction wells are also termed
horizontal drains, directional drains, hydraugers, or hydro-augers. In geotechnical engineering,
the term horizontal drains is typically used.
Vertical groundwater extraction wells are also termed pumping wells or dewatering wells.
Dewatering wells are installed using conventional well-drilling rigs using such drilling methods
as air or wet rotary tri-cone, auger, percussion, or sonic. Extraction well installation needs to be
designed and field-supervised by a licensed Professional Geologist, Engineering Geologist or
Geotechnical Engineer. Wells would be located based on an understanding of area
hydrogeology and stratigraphy.
4.3.2 Stormwater Control
Preventing stormwater infiltration is a key to reducing overall slope failure and ongoing surface
water loading to the project area. Stormwater originating upslope in Portuguese Canyon,
Paintbrush Canyon, and Ishibashi Canyon (east of Peacock Flat) has historically been flowing
directly into the head scarp of the PBLC just south of Burma Road where surface fractures are
present.
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Stormwater infiltration also recharges groundwater, to varying degrees, in the upper, central,
and lower canyon areas, which then flows in the subsurface downgradient to the southeastern
PBLC area where land movement is the greatest. Stormwater with the potential to result in
significant recharge in these areas should be captured and/or controlled, and discharged to the
ocean to prevent future recharge to surface fractures and groundwater.
Stormwater discharge from lower Klondike Canyon also recharges groundwater in the vicinity of
the southeastern Red Zone near where land movement is typically occurring at the greatest
rate. Stormwater in lower Klondike Canyon should be captured and discharged to the ocean to
prevent further groundwater recharge to this area of the PBLC.
GRAs that are used to address stormwater control can include one or any combination of
surface water infrastructure such as box culverts, channels, gabions, drainage ditches,
subdrains, velocity or energy dissipation structures, sedimentation basins, pipes, and
drainways. Much of this type of regional drainage infrastructure is typically constructed with
concrete, supplemented with metal or plastic piping, and designed for gravity flow.
However, due to the sensitive surrounding flora and fauna, alternatively, geotextiles and
engineered composite materials, such as geosynthetic clay liners (GCLs), can be used for
stormwater control where applicable in areas requiring substantial infiltration control. GCLs and
geotextiles can be used in constructed or restored wetlands environments or stream restoration
designs. Stormwater control GRAs also include segmented pre-fabricated channels that can be
specified, transported to a work area, and connected in series to form a streamway or channel
with controlled flow.
Surface water control measures also includes infilling of surface fractures on an annual basis as
a maintenance item before winter rains commence. Surface fractures in the PBLC head scarp
area can be filled in a number of ways, for example a grouting operation involving a long-reach
boom pumping truck delivering a slurried earthen filler material. The principal goal is to remove
preferential pathways through which rain or runoff water can rapidly percolate to the deep
subsurface past the zone of plant root uptake and subsequent transpiration.
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4.3.3 Enineered Slope Stabilization Measures
Numerous engineering measures for slope stabilization are currently in use in California. The
feasibility of implementation regarding a specific engineering measure depends upon several
factors. For example, in some situations, an extent of landsliding, geologic and groundwater
conditions, the composition of the landslide mass, and/or the thickness of the landslide mass
may limit implementation of a certain measure, while in other cases, terrain, topography, the
cost of implementation and maintenance and/or environmental constraints may be a deciding
factor. Engineered slope stabilization measures that could be considered for PBLC include the
following:
• Buttressing (engineered fill)
• Mechanically stabilized earth (MSE) wall
• Drilled piers (caissons)
4.3.4 Eliminate Septic System Discharge
As discussed in Section 3.6.1, septic tanks contribute a significant amount of groundwater
recharge in relatively dry water years. A centralized sewer system that eliminates septic tanks
in the PBLC area would significantly reduce future dry weather groundwater recharge. A
centralized sewer system is needed in portions of both the City of Rancho Palos Verdes and the
City Rolling Hills within the Portuguese Bend watershed (Figure 7).
The properties within the PBLC area between Peppertree Drive and PVDS currently use septic
tanks. A centralized sewer system would be beneficial in this neighborhood that is directly
adjacent to the northwest portion of the project area. Recharged groundwater in this
neighborhood flows downgradient directly into the project area.
The properties northeast of the PBLC area and south of Crest Road, primarily in the City of
Rolling Hills, currently use septic tanks. A centralized sewer system would be beneficial in this
neighborhood that is directly upgradient of the PBLC. Recharged groundwater in this
neighborhood eventually flows downgradient into the project area. It is recommended that the
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City of Rancho Palos Verdes encourage the City of Rolling Hills to construct a centralized sewer
system.
4.3.5 Coastal Erosion Control
An offshore breakwater could be installed in Portuguese Bend east or southeast of Inspiration
Point to dissipate offshore wave energy and reduce coastal wave-cut bluff erosion. This option
was studied in detail by the USACE to address marine habitat restoration in an FS dated 2000
(USACE, 2000).
4.4 Identification and Screening of Technology Alternatives
This section describes technologies commonly used in industry to address the RAO. This
section also provides an initial screening of these technologies to identify and eliminate
technologies that have a sufficiently obvious flaw, based on known conditions, such that it can
be determined early on in the remedy selection process that the technology could not be
reasonably implemented. Technologies that are retained as the result of the analysis presented
in this section are then carried forward to the detailed analysis of technology alternatives. Prior
to implementation, the alternatives would require further engineering analysis, reports, and
project plans. Screened technologies discussed below are also compared to effectiveness,
implementability, and cost criteria in Table 2.
4.4.1 Stormwater Control Option 1 – Repair Existing Corrugated Piping System
4.4.1.1 Description
The existing CMP system in the PBLC area could be repaired to capture stormwater and direct
discharge to the ocean. The piping network was appropriately installed in the areas of greatest
stormwater flow along the axes of Paintbrush, Ishibashi, and Portuguese Canyons. The loose
piping segments could be re-connected and refurbished and/or replaced so that the overall
system would be reinstated in its original design. Repairing and refurbishing and/or replacing
the piping would be a relatively straight-forward task with readily available equipment and labor.
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4.4.1.2 Screening Summary
The existing piping network has been out of maintenance for nearly 20 years. When originally
installed, the piping segments were relatively easily dismantled by continuing land movement in
the PBLC area. In addition, surface water flow in the PBLC was not fully captured by the piping
network since the upslope headworks were apparently under-designed. The piping diameter
may have been undersized as well. Also, the network likely did not cover enough area in the
PBLC. Though the original piping network was envisioned with the intention of capturing
stormwater and preventing groundwater recharge, it was installed as a preliminary engineering
solution. Resurrecting the former system does not address the design scale issues, and it
would not fully capture stormwater. If rebuilt, the metal piping would again be subject to
damage from ongoing land movement. A more substantially designed and flexible system is
needed for full stormwater capture and control. As a result, this option has been eliminated
from further consideration.
4.4.2 Stormwater Control Option 2 – Install Concrete Channels
4.4.2.1 Description
Traditionally, stormwater and flood control infrastructure is constructed with concrete channels
and associated metal or plastic piping. Stormwater flow is captured upslope and directed to
flood control basins where it infiltrates to groundwater or passes downgradient under gravity
flow to a supplemental basin or concrete channel or box culverts. Concrete channels and box
culverts are highly effective in capturing and directing stormwater flow and controlling design
floods of a pre-specified size and frequency. Concrete channels and culverts are an
established technology with available equipment, materials, and labor.
4.4.2.2 Screening Summary
Concrete channels and culverts are effective in geotechnically stable areas. However, where
there is land movement, concrete structures are prone to damage from tensional cracking,
shearing, subsidence, upheaval, and associated stresses. Once damaged, the channels would
no longer prevent groundwater infiltration. Routine maintenance and repair would not be cost-
effective in the long term. In addition, concrete structures do not typically allow for native habitat
to thrive nor do they receive widespread aesthetic acceptance. However, concrete structures
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are highly effective and efficient on controlling flow and may be appropriate in some portion of
the PBLC area such as the canyons south of Burma Road, or in mid-canyon areas that are not
prone to land movement. As a result, this option has been retained for further consideration in
limited areas of the PBLC.
4.4.3 Stormwater Control Option 3 – Install Liner and Channel System
4.4.3.1 Description
A canyon liner system consisting of engineered flexible geotextile composite fabrics or GCLs
would allow for both stormwater infiltration control and habitat development within the PBLC and
Preserve properties. Some associated engineering components would also be needed in mid-
canyon high-flow or flow-convergence areas such as velocity dissipation structures, flow control
channeling, streambank stabilization, vegetated gabions, or subsurface piping. Portions of
Portuguese, Paintbrush, and Ishibashi Canyons would be lined to direct flow away from the
PBLC head scarp area and away from the Project Area. High-flow in the mid-canyon area near
Burma Road would be captured and directed by gravity flow into a single channel downgradient
that ultimately connects to piping under the PVDS that discharges into the ocean. The flexible
composite fabrics are not prone to damage from land movement. The mid-canyon flow control
structures would be installed where land movement is minimal and acceptable. Habitat could
be partially integrated into the design of the canyon liner system. This option could be installed
with readily available equipment, materials, and labor, and designed to comply with the
minimization measures set forth in the City’s NCCP/HCP.
4.4.3.2 Screening Summary
This option would effectively prevent stormwater infiltration and groundwater recharge while
allowing for habitat establishment within the PBLC and Preserve properties. This technology is
readily available and could be cost-effectively installed and maintained, and could be designed
to comply with the minimization measures set forth in the City’s NCCP/HCP. Once installed, the
structures would be structurally flexible and not prone to damage from land movement. For
these reasons, this option has been retained for further consideration.
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4.4.4 Stormwater Control Option 4 – Seal Surface Fractures
4.4.4.1 Description
This option involves using a long-reach boom truck and/or conventional pumping truck, or other
method, to deliver a slurried earthen material to major surface fractures in the PBLC head scarp
area and other key areas where surface water infiltration needs to be minimized. A survey of
fractures and fracture sealing would be conducted on an annual basis as a maintenance item
before winter rains commence.
4.4.4.2 Screening Summary
This option could be conducted with limited or no impacts to existing habitat, with staging placed
in disturbed areas, and would help reduce groundwater recharge in the project area and in the
head scarp area. This technology is readily available and could be implemented for reasonable
cost with industry standard equipment, materials, and labor. For these reasons, this option has
been retained for further consideration.
4.4.5 Subsurface Dewatering Option 1 – Groundwater Extraction Pits
4.4.5.1 Description
This option involves completing semi-permanent linear excavations of subsurface soils below
groundwater in order to facilitate groundwater extraction from low-permeability soils over the
long term. Excavations would be completed with a roughly rectangular configuration where
groundwater extraction is needed in the southeastern PBLC area within the project area.
Extraction pits are effective in relatively low permeability formations as they allow for slow
groundwater seepage into the pit and incremental extraction by automated pumping to the
surface. Typically, multiple long pits aligned in parallel would be needed to effectively dewater a
relatively large area. Groundwater extraction pits are typically installed where the depth to
groundwater is less than 25 feet below grade so that excavation engineering and groundwater
extraction is less complex. However, deeper pits are also possible.
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4.4.5.2 Screening Summary
Groundwater extraction pits can be effective over the long term in low permeability formations
where groundwater extraction through traditional pumping wells is too problematic due to very
low well yields. However, multiple pits would likely be needed in the relatively large project area
and vicinity. Multiple aligned pits would be fairly disruptive to the existing properties.
Excavations are also inherently hazardous and require significant safety engineering during
design, implementation, oversight, and long-term maintenance. In addition, the depth to
groundwater in the PBLC area exceeds 50 feet below grade, further complicating this option
and significantly increasing the implementation cost. For these reasons, this option has been
eliminated from further consideration.
4.4.6 Subsurface Dewatering Option 2 – Groundwater Extraction Wells
4.4.6.1 Description
Vertical groundwater extraction wells are a proven and traditional technology for groundwater
dewatering. Typically, multiple wells are installed by drilling rig in a network pattern to
effectively extract groundwater from a design target area and depth. The radius-of-influence
(ROI) of each individual well is estimated from field measurements and coupled with the ROI
from adjacent wells so that the entire well network covers the target area with some ROI
overlap. Downhole electrical submersible pumps would deliver groundwater to the surface for
ultimate gravity flow or surface pump-assisted gravity flow to the ocean. Downhole pumps
require electrical power. Wells installed in key areas and depths can relieve subsurface
artesian pressure which can alleviate land movement.
4.4.6.2 Screening Summary
While extraction wells have been successful in the adjacent Abalone Cove area, extraction wells
have had limited success historically in the PBLC area due to low soil permeability, low well
yields, and pump clogging due to fine sediments and probable iron bacterial growth. Wells are
also prone to deformation or vertical shearing due to ongoing land movement. In addition, the
depth to groundwater in some portions of the PBLC exceeds 100 feet, which significantly
increases drilling, well installation, and operational costs.
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However, extraction wells can be very effective if installed in an area of little or no land
movement or where groundwater is present in relatively high permeability soils. Wells would be
more effective in historically slide-prone areas once land movement is significantly reduced
through other technologies. Wells could effective if coupled with other technologies such as
stormwater control. In addition, extraction wells are one of the few cost-effective technologies
actually available for subsurface dewatering. Extraction wells also required a relatively low
surface footprint for implementation, and less for operation, this being compatible with habitat
conservation and aesthetic goals. For these reasons, this option is retained for further
consideration.
4.4.7 Subsurface Dewatering Option 3 – Directional Subsurface Drains
4.4.7.1 Description
Directional subsurface drains are also termed hydraugers, hydro-augers, horizontal wells, or
horizontal drains. This technology involves the installation of relatively long, linear well casing
inclined to grade and extending up to 1,500 feet in the subsurface where conditions allow. The
casing is slotted like a vertical well screen so that groundwater passively enters the screen slots
then flows under gravity to the wellhead where it is directed to a pipe to the ocean. Several
lengths of slotted well casing can be installed from one work area as multiple runs of separate
slotted casing are oriented in a radial fan-like pattern extending up and into subsurface soils.
Horizontal extraction wells could be installed at several locations in the project area and in the
greater PBLC area where subsurface groundwater needs to be extracted. Drain casing can
also be installed with relatively large outer casing covering smaller inner casing to help promote
longevity and stability of the drain in a subsurface environment prone to land movement.
4.4.7.2 Screening Summary
Directional drains have a number of advantages for the PBLC area. Numerous drains can be
installed from one work area, and the resulting infrastructure is below grade so that no surface
habitat is disturbed above the casing. No pumps or electrical components are needed as
groundwater passively enters the drains and flows under gravity to an exit point at the work
area. Several drains could be installed from the coastal bluff south of PVDS that would extend
beneath the road and into and under the project area and other key areas where groundwater
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needs to be extracted. Additional drains could be installed further north at the base of the
slopes in the upper project area to extract groundwater in the mid-canyon areas. Drains could
be installed to cover nearly the entire project area subsurface if needed at a specified depth or,
perhaps, multiple depths. In addition, if aligned parallel with or sub-parallel to the primary
direction of regional land movement, drain casing would be less susceptible to shearing and
deformation due to land movement compared to vertical wells. As land movement eventually
slows due to dewatering, however, both wells and drains would be more stable over time.
The challenge would be where drains are needed at significant working depths such as depths
approaching 100 feet below grade or more. The drilling and casing installation work area
typically must be at the lowest point of elevation so that the casing can be inclined to grade to
enable gravity flow. For example, if groundwater extraction is required at a significant depth
below grade in relatively flat terrain, the work area must be designed within a temporary
excavation in order to achieve the appropriate geometry during installation. In some cases,
directional drilling from the surface can be used to help accommodate deeper casing depths.
Although working depth can complicate casing installation, this technology is cost effective, has
relatively little operation and maintenance, can cover large areas, and is highly effective in
groundwater dewatering. Moreover, minimal habitat loss would occur with this option, and like
vertical groundwater extraction wells, directional drains are one of the few cost-effective
technologies actually available for subsurface dewatering. For these reasons, this option is
retained for further consideration.
4.4.8 Engineering Slope Stabilization - Buttressing (Engineered Fill)
4.4.8.1 Description
Landslide mitigation by buttressing is probably the most commonly used method of landslide
stabilization in California. Depending on the size and shape of the landslide and borrow source
materials available, a relatively large buttress might be required. In some cases, especially
where space for construction of buttress fill is limited, other, complementary engineering
measures might be required. These measures might include soil (i.e., engineered fill)
reinforcement by means of geogrids and stabilization of temporary cuts for buttress fill
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construction by soil nails or rock anchors. These measures allow for construction of buttress
fills with nearly vertical slopes and very steep temporary cuts required for construction of these
slopes. Leighton (2000) proposed a major buttress along the coastline south of PVDS that is
nearly half a mile across and a smaller buttress along the southern and northeastern perimeter
of the project area.
4.4.8.2 Screening Summary
Buttress fills, when properly sized, keyed, benched and constructed, in most cases, stabilize
landslides for an extended period of time. Slope movements, including lateral displacements,
settlement and creep are, in most cases, minimal.
Past studies (e.g., Leighton, 2000) considered construction of a very large buttress fill to
mitigate the PBLC. Based upon review of past studies and the results of preliminary evaluation
of slope stability using a three-dimensional model, it was confirmed that a relatively large
buttress fill would be required for the PBLC. Due to location and size constraints, such a
buttress fill would require keying below groundwater which, in turn, would require dewatering
during construction. Due to its relatively large size, a buttress fill would be significantly
disruptive to protected habitat and residents during construction and would likely not be
aesthetically acceptable after construction. Construction of a buttress would be burdensome
and disruptive to regional transportation for an extended period of time. For these reasons, this
option has been eliminated from further consideration.
4.4.9 Engineering Slope Stabilization Measures - Mechanically Stabilized Earth Wall
4.4.9.1 Description
Mechanically stabilized earth (MSE) walls (gravity earth-retaining walls) are a common and
effective technology when applied in the appropriate geotechnical setting. MSE walls have
been successfully applied to mitigate slope failure at numerous locations in California. An MSE
wall is basically surface soil stabilized with engineered components such as reinforcing
geotextiles, panels, or precast blocks installed downslope as a support or anchoring structure to
mitigate upslope land movement or to counter forces associated with an upslope containment
(such as from water storage). One of the primary advantages of MSE walls is that they can be
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constructed as modular components in a relatively short period of time compared to other
technologies. MSE walls are commonly constructed in roadside slope stabilization projects, as
secondary tank containment, and in dams and levees.
4.4.9.2 Screening Summary
MSE walls are cost-effective and can be rapidly constructed to mitigate slope failure or counter
design forces upslope in appropriate environments such as where the rupture surface is
relatively shallow, and/or where substantial footings or keying to stable bedrock is not required.
At the PBLC, the depth to the basal rupture surface exceeds 60 feet in some areas. A surficial
MSE wall would not stabilize land movement originating at depth. Although MSE walls are
attractive from a cost perspective and are relatively simple to install, due to the depth to the
basal rupture surface at the PBLC, along with the relatively large PBLC area that requires
stabilization, MSE walls are not an appropriate alternative and will not be considered further.
4.4.10 Engineering Slope Stabilization Measures – Drilled Piers (Caissons)
4.4.10.1 Description
Soil improvement techniques like piles, rock anchors, soil nails, and drilled piers (caissons), are
commonly used to stabilize slopes and/or to mitigate areas affected by landsliding. Given the
size of the area affected by landsliding, the only potentially feasible, soil-improvement based
slope mitigation option for the PBLC is mitigation with drilled piers. Drilled piers (caissons) are
constructed by drilling and installing vertical reinforcement bars surrounded by poured concrete.
Several rows of closely-spaced piers (typically separated by a distance equal to 1.5 to 3 pier-
diameters) are installed along the bottom third of sliding mass below the basal rupture surface.
Drilled piers must extend below the basal failure surface (the total depth depends on the
mechanical properties of the material below the basal failure surface). Drilled piers with
diameters of up to 8 feet and up to 60 feet long have been installed at various sites across
coastal California in the past, including the PBLC (Section 2.1).
4.4.10.2 Screening Summary
Drilled piers can be installed in areas where access is limited or where there is not enough room
to construct a properly keyed and benched engineered buttress. Preliminary evaluation,
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consistent with past studies, indicates that numerous large diameter drilled piers would be
required for PBLC mitigation. In addition, the required caisson depth, advanced below the basal
failure surface, would be excessive (at many locations over 60 feet). Therefore, the cost of
implementation of this measure, and the associated disruption to the environment, traffic, and
residents, is a basis for elimination of this remedial measure from further consideration.
4.4.11 Centralized Sewer System
4.4.11.1 Description
As discussed in Section 4.5.2, septic tanks contribute a significant amount of groundwater
recharge in relatively dry water years. Septic tanks are located at properties in both the City of
Rancho Palos Verdes and the City of Rolling Hills. A centralized sewer system that eliminates
septic tanks in the PBLC area would significantly reduce future dry weather groundwater
recharge. Residential septic systems would be incrementally and systematically removed only
once a new centralized sewer is installed along streets in the target neighborhoods. The new
sewer system would be installed under the center or along the side of existing streets and
connected by laterals to each home within the network. Sewer line flow would ultimately be
directed to a centralized sewer treatment plant such as the Sanitation Districts of Los Angeles
County Joint Water Pollution Control Plant (JWPCP) in Carson, California. This option would
have to be fully evaluated in a separate engineering study to develop specific objectives, design
options, costs, and regulatory requirements for both the City of Rancho Palos Verdes and the
City of Rolling Hills.
4.4.11.2 Screening Summary
This option would help reduce groundwater recharge in both the immediate vicinity of the
Project Area and in the upper canyon areas over the long term. This technology is readily
available and could be installed and maintained with industry standard equipment, materials,
and labor. For these reasons, this option has been retained for further consideration.
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4.4.12 Coastal Erosion Control (Breakwater)
4.4.12.1 Description
An offshore breakwater installed in Portuguese Bend east or southeast of Inspiration Point
would dissipate offshore wave energy and reduce coastal bluff erosion. This engineered
structure would consist of a containment dike or similar feature. This option was studied in
detail by the USACE in their FS dated 2000 (USACE, 2000).
4.4.12.2 Screening Summary
While this option would reduce wave erosion along the bluff south of PVDS, overall landslide
mitigation would not be addressed. As a result, the landslide complex would continue to
advance generally towards the south after breakwater construction. For this reason, a
breakwater option has not been retained for further consideration.
4.4.13 Summary of Retained Technologies
The following technology alternatives have been retained for detailed evaluation, after
completion of the screening process:
• Stormwater Control – Concrete Channels
• Stormwater Control – Flexible Liner System and Components
• Stormwater Control – Seal Surface Fractures
• Subsurface Dewatering – Groundwater Extraction Wells
• Subsurface Dewatering – Directional Subsurface Drains
• Eliminate Septic System Discharge – Centralized Sewer System
The detailed analysis of each option is presented in the following section.
4.5 Detailed Analysis of Remedial Technologies
The evaluation criteria that were used to conduct an analysis of the candidate alternative
technologies are listed below:
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• Overall protection of human health and the environment
• Compliance with ARARs
• Long-term effectiveness and permanence
• Short-term effectiveness
• Implementability
• Cost
• State and community acceptance
The options presented in this section are ranked and numerically scored for each evaluation
criteria (Table 3). The individual scores are summed to arrive at a total technology score. The
options that received the higher total scores and relative lowest cost were identified as a
preferred option for the City’s consideration. Approximate order-of-magnitude costs for each
option are included in Table 4.
4.5.1 Concrete Channels
• Overall Protection of Human Health and the Environment. Concrete channels are
protective of human health but can impact the natural environment once constructed.
Construction permanently displaces otherwise native habitat and has an adverse impact
on the aesthetic value of the open Preserve land.
• Compliance with ARARs. This option would likely meet most of the requirements of the
identified ARARs. However, converting a blue line stream such as the upper canyon,
mid-canyon, or lower canyon areas into a concrete channel would likely not be a
permitted project.
• Long-Term Effectiveness and Permanence. Concrete channels would be effective and
permanent in the long term if built in areas with little to no land movement.
• Short-Term Effectiveness. Concrete channels would be effective in the short term if built
in areas with little to no land movement.
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• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor.
• Cost. This option does not involve specialty equipment, materials, or labor and is
routinely implemented for stormwater control in appropriate areas. As a result, the
option should not be cost-prohibitive.
• State and community acceptance. This option is likely unacceptable to the state and the
community because it would significantly alter the appearance of the Preserve properties
and permanently eliminate habitat acreage within the Preserve.
This option would be effective and could be installed for manageable costs. Over the longer
term, maintenance costs would be high to repair damage caused by land movement. However,
it would likely not be permitted within a native habitat area. In addition, it is not aesthetically
acceptable for placement within a preserve with protected habitat. As a result of the detailed
analysis of this option discussed above, it has been eliminated from further consideration.
4.5.2 Liner and Channel System
• Overall Protection of Human Health and the Environment. Flexible material lining the
canyons, where appropriate, would be protective of human health and integrated into the
environment after construction. Engineered substrate could be incorporated into the
design to allow for acceptable habitat development within the lined stormwater channel
network.
• Compliance with ARARs. This option would likely meet most or all of the requirements
of the identified ARARs. It is anticipated that work within a blue line stream could be
permitted in part under a stream restoration program.
• Long-Term Effectiveness and Permanence. This option would be effective and
permanent in the long term. The proposed materials are flexible and are not susceptible
to damage from land movement. The surface area can be planted with native vegetation
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that can be designed to accommodate various root systems depending on the depth of
the top soil.
• Short-Term Effectiveness. This option would be effective and permanent in the short
term. If land movement occurs early in the program before longer term land movement
is significantly reduced, a flexible liner system is designed to withstand damage by
allowing some liner movement.
• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor.
• Cost. This option does not involve specialty equipment, materials, or labor and is
routinely implemented for infiltration control in appropriate areas. As a result, the option
should not be cost-prohibitive.
• State and community acceptance. This option would likely be acceptable to the state
and to the community because it partially integrates habitat and stream restoration into a
design for stormwater capture and control.
4.5.3 Seal Surface Fractures
• Overall Protection of Human Health and the Environment. Sealing surface fractures
each year in the PBLC head scarp and project area, where appropriate, would be
protective of human health and the environment as the contribution to overall land
movement due to stormwater infiltration would be reduced.
• Compliance with ARARs. This option would likely meet most or all of the requirements
of the identified ARARs.
• Long-Term Effectiveness and Permanence. This option would be effective and
permanent in the long term. Additional sealing may be needed each year if additional
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fractures are identified. Eventually as land movement is significantly reduced, the need
to continue fracture sealing would become increasingly reduced.
• Short-Term Effectiveness. This option would be effective and permanent in the short
term once sealing material is introduced into fractures.
• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor. The staging area would take up
relatively minimal surface area with minimal impact to protected habitat.
• Cost. This option does not involve specialty equipment, materials, or labor and is
routinely implemented for infiltration control in appropriate areas. As a result, the option
should not be cost-prohibitive.
• State and community acceptance. This option would likely be acceptable to the state
and to the community because it does not significantly impact the surrounding surface
environment or habitat, and provided that the staging area is located where little to no
impact to protected habitat would occur.
4.5.4 Groundwater Extraction Wells
• Overall Protection of Human Health and the Environment. Groundwater extraction wells
are protective of human health and the environment when properly designed, installed,
and maintained. This option would result in relatively minimal impacts to the native
habitat or open land.
• Compliance with ARARs. Well installation is routinely permitted and would meet
requirements of the identified ARARs.
• Long-Term Effectiveness and Permanence. Groundwater extraction wells have been
problematic over the long term in the PBLC area due to clogging and damage due to
land movement. Wells could be sustainable and permanent over the long term if the
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clogging issue can be resolved through such measures as periodic sterilization with
oxidants and redevelopment. In addition, groundwater yield has been problematically
low in the PBLC area due to naturally occurring low permeability soils in the subsurface.
However, if installed in the appropriate area and at the appropriate depth where soils are
sufficiently permeable and where groundwater is present, extraction wells are highly
effective in removing subsurface groundwater.
• Short-Term Effectiveness. Wells are effective over the short term if installed and
maintained where groundwater is present in sufficiently permeable soils.
• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor. This technology is one of the few
available for subsurface dewatering. However, low permeability soils can be problematic
in the subsurface at the PBLC.
• Cost. This option does not involve specialty equipment, materials, or labor and is
routinely implemented for infiltration control in appropriate areas. As a result, the option
should not be cost-prohibitive.
• State and community acceptance. This option would likely be acceptable to the state
and to the community because wells currently exist within the PBLC, and in adjacent
areas, and are installed and maintained within a relatively small area footprint.
4.5.5 Directional Subsurface Drains
• Overall Protection of Human Health and the Environment. Horizontal groundwater
extraction wells are protective of human health and the environment because they are
installed nearly entirely in the subsurface. Installation can be conducted within a
relatively limited area footprint with relatively minimal impacts to the native habitat or
open land, and would not result in an adverse aesthetic value because the drains are
mostly located below the surface.
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• Compliance with ARARs. Horizontal well installation is routinely permitted and would
meet requirements of the identified ARARs.
• Long-Term Effectiveness and Permanence. Horizontal groundwater extraction wells are
effective over the long term because they are essentially a passive technology with no
moving parts, relatively limited operation and maintenance, and are mostly underground
where the potential for damage from surface activities is eliminated. Groundwater
continues to be extracted as long as the well is not damaged from lateral land movement
transverse to the well casing. Horizontal wells can be installed with concentric casings
aligned parallel to prevailing land movement to help minimize damage from land
movement. As the wells remove groundwater land movement is anticipated to be
significantly reduced incrementally over time so that the potential for well damage is also
incrementally reduced. As with vertical wells, horizontal wells could be sustainable and
permanent over the long term if the clogging issue can be resolved through such
measures as periodic sterilization with oxidants and redevelopment.
If installed in the appropriate area and at the appropriate depth where soils are
sufficiently permeable and where groundwater is present, horizontal extraction wells are
highly effective in removing subsurface groundwater over the long-term. This
technology has not been implemented in the PBLC area before, although it is highly
effective when appropriately installed and monitored.
• Short-Term Effectiveness. Horizontal wells are also effective over the short term if
installed where groundwater is present. In some installations, groundwater flow into the
horizontal wells can take up to several months before discharge is observed.
• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor. This technology is also one of the few
available for subsurface dewatering. However, low permeability soils can be problematic
in the subsurface at the PBLC.
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• Cost. This option does not involve non-standard specialty equipment, materials, or labor
and is routinely implemented for groundwater extraction control in landslide repair or
landslide-prone areas. Multiple horizontal wells, directed out radially and extending up
to approximately 1,000 feet or more of lateral length, can be installed from one work
area. As a result, this option is highly cost-effective.
• State and community acceptance. This option would likely be acceptable to the state
and to the community because horizontal wells are mostly underground, out of sight, do
not impact habitat or open space, and are installed and maintained within a relatively
small area footprint. Only relatively minor surface piping would be associated with each
wellhead to direct captured groundwater by gravity flow to a nearby surface water
channel or pipe discharge to the ocean.
4.5.6 Centralized Sewer System
• Overall Protection of Human Health and the Environment. Centralized sewer systems
are protective of human health and the environment as they control and contain raw
sewage flow to regional treatment plants instead of directing the liquid flow into the
subsurface environment.
• Compliance with ARARs. This alternative would likely meet most or all of the
requirements of the identified ARARs. This option likely involves significant permitting
from multiple jurisdictions, however.
• Long-Term Effectiveness and Permanence. This option would be effective and
permanent in the long term. Some periodic maintenance is required.
• Short-Term Effectiveness. This option would be effective and permanent in the short
term once constructed.
• Implementability. This option is standard technology that is easily implemented with
readily available equipment, materials, and labor.
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• Cost. This option does not involve specialty equipment, materials or labor and is
routinely implemented in new developments and in retro-fit areas. This option involves
significant planning, permitting, design engineering, and construction work, and, as a
result, costs are relatively high. Moreover, permitting and construction would occur in the
City of Rancho Palos Verdes and the City of Rolling Hills.
• State and community acceptance. This option would likely be acceptable to the state
due to the elimination of ongoing liquid infiltration that contributes to regional land
movement. While the community will understand and support cessation of land
movement, conversion costs from OWTS to city sewer will likely be an issue that would
need to be addressed by City of Rancho Palos Verdes and the City of Rolling Hills.
4.6 Preferred Options
4.6.1 Description and Conceptual Design
Based on the evaluation and discussion presented in the previous sections, the following
preferred options have been identified for the City’s consideration:
• Seal Surface Fractures
• Directional Subsurface Drains
• Flexible Liner System and Components
• Groundwater Extraction Wells
• Centralized Sewer System
The sequence of the remedy options has been organized to correspond with an iterative
construction cycle or a phased-approach to overall design, construction and installation. That is,
sealing surface fractures a relatively straight-forward and cost-effective remedy that could be
readily implemented before other options are pursued or while other options are in design,
permitting, or construction. Second, directional drains are a conventional and cost-effective
solution that could be installed while the more complex stormwater control liner and channel
system would be in design, permitting, or construction. Directional drains would be installed in a
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phased manner to allow for additional drains installed over time once earlier designs are
installed, pilot-tested, and assessed on its effectiveness.
Finally, after key fractures are sealed, directional subsurface drains are in place, and
stormwater control is in place, the remedy program may be supplemented with an expansion of
the existing groundwater extraction well network. Wells would be installed last in the sequence
so that potential well damage from ongoing land movement would be minimized as the earlier
components incrementally take effect.
The first three remedy options (sealing fractures, directional drains, and stormwater
liner/channel system) would be pilot-tested before full-scale design and construction to allow for
design refinement and adjustment as needed based on field conditions. Pilot testing is
discussed below in Section 4.6.3. Each remedy component is further described in the following
subsections.
4.6.1.1 Seal Surface Fractures
This technology consists of in-filling existing surface fractures on an annual basis primarily in the
vicinity of the project area (Red Zone) and in the PBLC head scarp area to reduce stormwater
infiltration to groundwater. Other areas of the PBLC such as south of PVDS or within the
interior of the slide area itself could also be included if appropriate. Relatively large fractures
would be infilled before the rainy winter season each year using a long -reach pumping truck,
conventional pumping rig, or other method. Surface fractures would be identified in advance
each fall through an on-site visual inspection survey, recent aerial photograph review, or
potentially, with photographic data collected with an aerial drone fly-over.
4.6.1.2 Directional Subsurface Drains
Directional drains have the potential to have a significant effect on lowering the groundwater
surface within the PBLC project area. Drains would be installed in a phased approach to target
groundwater removal in the southern project area where land movement has historically been
measured at the greatest rate. Drains could be installed at two or more locations at the
southern edge of the coastal bluff south of Palos Verdes Drive, for example, and would be
drilled radially approximately 1,200 to 1,500 feet northwest, north, and northeast extending
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beneath PVDS (Figure 14). Drains in this area would be installed using a conventional, track-
mounted horizontal drilling rig that can safely and reliably access the rocky beach area. Other
drains could be installed north of the beach from low-lying areas south of PVDS. The drain
design would have to include infrastructure to collect and discharge groundwater flow from the
drains, such as piping runs to an ocean discharge location on the beach.
An engineering study would need to be prepared to support identification of exact drilling
locations and drain installation geometry. Additional data gaps related to this and other options
are discussed in Section 4.6.2.
4.6.1.3 Liner and Channel System
This technology consists of the following components (Appendix D):
• Canyon Liner
• Lapped Liner System
• Lapped Channel Liner Under-Drain System
• Native Vegetation
The ultimate goal of this technology is to minimize or eliminate stormwater infiltration and
percolation to groundwater in the Portuguese Bend watershed and in the PBLC Project Area.
The canyon liner would extend just north of the Burma Road Trail at an appropriate distance
upgradient into Portuguese, Paintbrush, and Ishibashi Canyons in order to capture and control
stormwater surface flow and direct it to the ocean (described below) (Appendix D). The canyon
liner system as envisioned would be an impervious layer with an underdrain and an armored
stone riprap surface in relatively high surface water flow segments. Lower Portuguese Canyon
in the northern Project Area would also be lined and the canyon liners can be vegetated to
blend into the native habitat. The depth of the top soil will determine the size of the feasible root
system supporting the native habitat. The subsurface liner material, such as engineered
geomembrane, could be expected to have a lifetime expectancy of at least several hundred
years (Benson, 2014).
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The canyon liner would direct flow into a lower channel installed across the northern edge of the
PBLC area and leading under gravity flow to a road culvert under PVDS (Appendix D). Similar
to the canyon liner, the outlet channel would be installed with an underlying lapped geotextile
liner and surface rock armoring. The outlet channel could also be vegetated to blend into the
native habitat. Vegetation islands can be installed mid-stream where the overall design and
flow conditions allow.
This option would also include a drainage and engineering study to support a final design that
will promote surface water flow along the northern roadside of PVDS where storm water has
historically been ponding and infiltrating to groundwater in the Red Zone area.
Ultimately, additional areas in the adjacent watersheds could also be lined, such as eastern
Altamira Canyon or lower Klondike Canyon, where stormwater continues to infiltrate to
groundwater in the vicinity of the project area. The described liner and channel system is only a
conceptual design. A full engineering and hydrologic study would be needed to support final
design and sizing of the liner and channel system.
4.6.1.4 Groundwater Extraction Wells
Supplemental groundwater extraction wells would be installed in the project area once drains
and stormwater control are in place (Figure 14). Groundwater extraction wells would be
installed with conventional track-mounted or truck-mounted well drilling rigs using sonic drilling
methods. The sonic method is preferred since soil sampling and characterization can be
continually conducted while drilling commences, groundwater is readily observed, and well
installation can proceed without the potential for drilling-induced permeability reduction
associated with other methods such as mud rotary. Companion borings for geologic or
geotechnical investigation may also need to be completed in advance by other methods to
collect well design information such as geologic, stratigraphic, or hydrogeologic data.
Groundwater monitoring wells will also need to be installed to routinely monitor groundwater
levels in the PBLC area. At this conceptual stage of the overall project, based on the areal
extent of the PBLC area and historical well yields, it is estimated that approximately
25 extraction wells would be needed in the project area with a network of approximately 10 to
15 additional monitoring wells within and adjacent to the project area. The number, depth, and
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design of the extraction and monitoring wells would be based on site-specific aquifer testing
conducted to determine well design parameters as well as overall hydrogeologic and
stratigraphic data based on historical work or supplemental site investigation.
4.6.1.5 Centralized Sewer System
Approximately 2 miles of new subsurface sewer lines and associated manholes and junctions
need to be installed in the Portuguese Bend neighborhood east of lower Altamira Canyon and
west of lower Portuguese Canyon. This area includes those roads generally southeast of
Peppertree Drive and north of Palos Verdes Drive South (Figure 7). In addition, approximately
1.5 miles of new subsurface sewer lines are needed in the upper Portuguese Canyon
Watershed. New sewer lines are needed in this area where upper Portuguese Canyon extends
north to the northern watershed boundary at Crest Road and where upper Ishibashi Canyon
splits into four sub-canyons that extend east-northeast to the northern watershed boundary.
Both upper Portuguese Canyon and upper Ishibashi Canyon are located within the City of
Rolling Hills. The new sewer line installation would need to be synchronized with private lateral
installation and connection as well as septic system removal in both neighborhoods. The new
lines would likely be connected to nearby exiting lines that direct sewage to the Los Angeles
County Joint Water Pollution Control Plant (JWPCP) in Carson. New sewer line installation and
septic tank removal would have to be fully designed in a separate engineering study to develop
specific objectives, design options, costs, and regulatory requirements.
4.6.2 Data Gaps
In addition, the following final design input is needed, at a minimum, to develop a detailed scope
of work and engineering cost estimate for construction bidding for the City’s consideration:
• Hydrologic analysis and floodplain mapping
• Geologic, hydrogeologic, and stratigraphic characterization
Hydrologic analysis, floodplain mapping, and watershed modeling are needed to appropriately
characterize and specify the design flood for canyon lining and channel sizing engineering.
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These data include stream flow measurements, flood frequency, rainfall data analysis, and
related tasks.
Geologic, hydrogeologic, and stratigraphic data are needed to understand subsurface
conditions before drain and well drilling commences. Historical data are also needed, if
available, including extraction well construction data, extraction well production records, boring
logs, a master soil boring and well location map, groundwater elevation data (historical and
current), and groundwater quality sampling data.
Data gap information is typically further specified in a data gap investigation work plan that
outlines the required information and how it can be collected before final design engineering
commences.
4.6.3 Pilot Testing
The remedy options selected by the City should be pilot tested before full-scale implementation.
Pilot testing should be completed to simulate full-scale implementation as much as possible
while obtaining the design data needed to scale-up and cost the remedy for complete
implementation. Pilot testing should be completed before full-scale implementation of the
canyon liner and collector channel system, the surface fracture sealing, and subsurface drain
remedy options. Pilot testing and associated baseline and performance monitoring is typically
specified and detailed in a separate plan. The pilot test plan could be combined with the data
gap investigation work plan discussed above.
4.6.4 Approximate Implementation Costs
The approximate order-of -magnitude costs (2018 dollars) associated with the preferred
alternative is provided in Table 4. Estimated costs are based on industry literature where
possible and from professional experience with similar projects.
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4.6.4.1 Seal Surface Fractures
Pilot testing for a surface fracture sealing program is estimated to cost approximately $100,000.
Planning, permitting, construction and initial reporting for a full-scale program is estimated at
approximately $250,000. Operation and maintenance (O&M) (fracture sealing, monitoring, and
reporting each year thereafter) costs are estimated at approximately $50,000. Extended for
10 years (2018 dollars), O&M would cost approximately $625,000. The total cost for this option
is thus approximately $975,000.
4.6.4.2 Directional Subsurface Drains
Directional drains require a data gap investigation to characterize groundwater and identify the
appropriate stratigraphic zone for drain installation. Data gap investigation and pilot testing for a
drain program is estimated to cost approximately $656,000. Planning, permitting, construction
and reporting of a full-scale program of 10 drains extending 1,200 feet is estimated at
approximately $6.4 million. O&M (including monitoring and reporting each year thereafter) is
estimated at approximately $125,000. Extended for 30 years (2018 dollars) (without major
reconstruction) this component would cost approximately $11.7 million. Major reconstruction for
additional drains or replacement drains would be basically comparable to the initial program
cost rates and total costs.
4.6.4.3 Liner and Channel System
Pilot testing for a liner and channel system is estimated at approximately $512,000. Planning,
permitting, and construction of a full-scale program of lining the canyons (Portuguese,
Paintbrush, Ishibashi) with a perimeter channel and culvert directing flow to the ocean is
estimated to cost approximately $13.5 million. O&M (including monitoring and reporting each
year thereafter) is estimated at approximately $75,000. Extended for 30 years (2018 dollars)
(without major reconstruction) this component would cost approximately $16.8 million.
4.6.4.4 Groundwater Extraction and Monitoring Wells
Groundwater extraction wells require a data gap investigation to characterize groundwater and
identify the appropriate stratigraphic zone(s) for well installation. Data gap investigation and
pilot testing for supplemental groundwater extraction wells is estimated at approximately
$556,000 (supplemental to the drain data gap investigation). Planning, permitting, and
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construction of a full-scale program (20 wells to 200 feet with 10 companion monitoring wells
[30 wells total]) is estimated to cost approximately $4 million. O&M (including monitoring and
reporting each year thereafter) is estimated at approximately $325,000. Extended for 30 years
(2018 dollars) (without major reconstruction) this component would cost approximately
$12 million.
4.6.4.5 Centralized Sewer System
Residential sewer costs are approximately $200 per linear foot overall including manholes and
related infrastructure. Approximately 1.5 miles of sewer line are needed in the Portuguese
Bend neighborhood and approximately 2 miles of sewer line are needed in the upper
Portuguese Bend watershed area (within the City of Rolling Hills) (total of approximately
18,480 feet). Planning, permitting, and construction of a full-scale program in both the City of
Rancho Palos Verdes and Rolling Hills is estimated to cost approximately $5 million. O&M
(including monitoring and reporting each year thereafter) is estimated at approximately $50,000.
Extended for 30 years (2018 dollars) (without major reconstruction) this component would cost
approximately $7 million.
4.6.4.6 Total Estimated Project Cost
The estimated order-of-magnitude cost for all components of the preferred remedy totals
$31.3 million for initial planning, permitting, data gap investigation, pilot testing, design, and
construction. With O&M, monitoring, and reporting extended for 30 years (2018 dollars)
(without major reconstruction) the estimated order-of-magnitude cost totals $53.5 million.
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