CC SR 20240416 03 - Landslide Emergency Hydraugers
CITY COUNCIL MEETING DATE: 04/16/2024
AGENDA REPORT AGENDA HEADING: Regular Business
AGENDA TITLE:
Consideration and possible action to approve emergency work for the Portuguese Bend
Landslide.
RECOMMENDED COUNCIL ACTION:
(1) Continue this item to the May 7, 2024 City Council meeting.
FISCAL IMPACT: The recommended Council action has no fiscal impact.
Amount Budgeted: N/A
Additional Appropriation: N/A
Account Number(s): N/A
ORIGINATED BY: Ramzi Awwad, Public Works Director
REVIEWED BY: Same as above
APPROVED BY: Ara Mihranian, AICP, City Manager
BACKGROUND:
On March 19, 2024, after reviewing information presented that evening, including public
testimony, the City Council approved emergency work in the Portuguese Bend Landslide
(PBL) consisting of installing two emergency hydrauger arrays with five drains each, and
associated work. Due to the urgency, the City Council authorized the City Manager to
sign professional service agreements and contracts associated with the emergency work
as soon as they become available for eventual ratification by the City Council at its next
meeting. Also on March 19, 2024, the City Council d irected Staff to explore assisting the
two Geologic Hazard Abatement Districts (GHADs) - Abalone Cove Landslide Abatement
District (ACLAD) and the Klondike Canyon Landslide Abatement District (KCLAD) - with
in-kind services and financial assistance in the form of a loan for landslide mitigation
measures prepared by a licensed geotechnical engineering company and return to the
City Council for consideration.
Since the March 19 meeting, Staff have been working closely and expeditiously with its
geotechnical engineers, geologists, and project management team, along with various
branches of government, to proceed with the two emergency hydraugers. Additionally,
Staff have also been working closely with members of ACLAD and KCLAD to finalize the
City’s assistance package. Due to the complexities involved in finalizing the plans a nd
1
agreements described above, Staff is requesting that this agenda be continued to the
May 7 City Council meeting as discussed below.
DISCUSSION:
Emergency Hydrauger Construction Plans
Due to the accelerated increase in the rate of land movement in the Landslide Complex,
the City’s geotechnical engineering design consultant, Geo-Logic Associates, Inc. (GLA)
has been developing plans to implement emergency stabilization measures for the
Portuguese Bend Landslide (PBL), a sub-slide within the greater ancient Portuguese
Bend Landslide Complex. The following emergency measures focus on the fastest-
moving portion of the slide (approximate locations shown in Exhibit 1):
• Local fissure infilling and limited grading to allow access for construction
equipment.
• Four borehole sites to gather data for validating modeling assumptions and to
better estimate quantity and quality of groundwater to be removed.
• Emergency Hydrauger E-1 (Hydrauger E-1) consisting of an array of five
horizontally-drilled drains, associated temporary water storage and management
facilities, and drainage discharge lines.
• Emergency Hydrauger E-2 (Hydrauger E-2) consisting of an array of five
horizontally-drilled drains, associated temporary water storage and management
facilities, and drainage discharge lines.
Exhibit 1: Approximate Locations of Emergency Mitigation Measures
2
The City conducted a peer review of the Emergency Hydraugers Project through the City
Geologist consultant, Cotton, Shires & Associates, Inc. (Cotton Shires), to assure the best
possible outcome for the project considering the geological and access constraints. The
peer review led the City to consider investigating some alternate locations for Emergency
Hydrauger E-1 than what is shown in Exhibit 1 that may be more effective and durable.
Additionally, the peer review led to investigating the possibility that the hydrauger arrays
could be deployed in such a way that it also benefits the Klondike Canyon Landslide
(KCL). Further analysis is needed to determine the optimal location of Hydrauger E-1 and
whether it could be constructed to also benefit the KCL. At this time, further discussion is
needed between GLA, Cotton Shires, and KCLAD to conclude the best location for
Hydrauger E-1.
In any case, before starting construction of Hydrauger E-1, the computer model used to
design its vertical and horizontal alignment needs to be field validated because it relies
on assumptions based upon geologic and survey information from relevant past geology
reports and site characterization studies of the project area. Considering the significant
cost associated with the installation and maintenance of the hydrauger systems,
validation of these key assumptions and updating of the computer model is necessary to
maximize success. This will be achieved by a limited, targeted exploration boring program
that will be executed very shortly before the start of hydrauger installation.
The limited and targeted exploration boring program consists of the installation and short-
term monitoring of four multipurpose borehole sites with dual boreholes at each site.
These boreholes will be drilled vertically to an approximate depth of 150 feet below the
existing ground surface. The approximate location of these Hydrauger E-1 boreholes is
shown in Exhibit 1. Installation of the boreholes can proceed under the City Manager’s
emergency contract signing authority and brought back to the City Council for ratification.
This will minimize any delays while additional analysis on the location of Hydrauger E-1
is conducted.
Although time is of the essence, Staff believes the additional time by continuing this item
to May 7 will yield the most effective end result.
KCLAD and ACLAD Loan
ACLAD and KCLAD are GHADs created with the authority and responsibility to address
land movement in the Abalone Canyon Landslide (ACL) and KCL, respectively. ACLAD
and KCLAD are governmental districts, independent of the City, formed for the
prevention, mitigation, abatement, or control of a “geologic hazard”, which is defined as
an actual or threatened landslide, land subsidence, soil erosion, earthquake, fault
movement, or any other natural or unnatural movement of land or earth. ACLAD and
KCLAD have the ability to assess properties within their districts to fund their activities.
To date, the City has been coordinating very closely with ACLAD and KCLAD on their
various mitigation activities by providing support services and funding four dewatering
wells in ACLAD, south of Palos Verdes Drive South , based on a Council Agreement
dating back to the 1994 and renewed in 2000 . ACLAD and KCLAD representatives
recently indicated that their fund reserves are depleted, and additional funding is needed
3
before they can proceed with further landslide mitigation measures.
On March 19, 2024, the City Council directed Staff to explore assisting ACLAD and
KCLAD with in-kind services and financial assistance in the form of a loan for landslide
mitigation measures prepared by a licensed geotechnical engineering company.
KCLAD submitted to the City a five-step landslide mitigation plan prepared by WSP
Global Inc. (WSP) Senior Associate Engineering Geologist Scott Kerwin , a Certified
Engineering Geologist. The five-step plan is currently being peer reviewed by Cotton
Shires.
KCLAD requested a loan from the City in the amount of $1,917,500 with zero interest and
a re-payment term of 20 years. The KCLAD Chairperson indicated that KCLAD will be
working through the Proposition 218 process to consider increasing the assessment on
property owners to raise the funds to repay the loan. Additionally, KCLAD is applying for
congressional district grants to fund the remaining steps of the five-step plan. The City
and KCLAD are currently finalizing the details of the loan and additional tim e is needed
to complete the loan agreement and peer review.
ACLAD is continuing work on their plan and at this time, has not submitted a formal
request to the City for a loan with a plan prepared by a licensed geotechnical engineering
company. ACLAD is also applying for congressional district grants.
Thus, the City Council is being asked to continue this item to May 7, 2024 to allow time
to complete the KCLAD loan agreement and work with ACLAD on their plan and loan
agreement.
ADDITIONAL INFORMATION:
Landslide Town Hall Meeting
A landslide town hall meeting is scheduled for Wednesday, April 17, 2024 at 6:00pm at
the Ladera Linda Community Park. During the meeting, there will be presentations on
various aspects of the ancient Portuguese Bend Landslide Complex. The GHADs, utility
companies, and other partners will be included in presenting information at the town hall.
The town hall has been advertised via listserv, social media platforms, and other
communication conduits including the Landslide Working Group meetings.
Palos Verdes Drive South (PVDS) Roadway Repairs Update
As reported to the City Council on March 19, 2024, Staff are working (through consultants)
on developing construction plans to re-grade the “ski jump” area of PVDS to mitigate the
elevation difference that is increasing due to the rift/scarp that is formin g at that location.
The plans are continuing to progress and Staff are also working with consultants to plan
construction in a way that minimizes disruption to the approximately 15,000 daily vehicles
that use PVDS. In the interim, crews completed a smaller-scale repair so that the area
continues to be passable until the re-grading work is complete.
4
Roadway construction work that may result in the temporary closure of PVDS will not
proceed, provided a situational safety threat does not occur, without adequate public
notification and coordination with the Lomita Station, Los Angeles County Fire
Department, Palos Verdes Peninsula Unified School District, local homeowners
associations, Terranea, Trump National, and others to name a few.
CONCLUSION:
Staff recommends continuing this item to the May 7, 2024 City Council meeting to allow
additional time to optimize the location of Hydrauger Array E-1 and finalize the details of
the financial assistance package to KCLAD and ACLAD.
ALTERNATIVES:
In addition to Staff recommendation, the following alternative actions are available for
the City Council’s consideration:
1. Take other action, as deemed appropriate.
5