Chapter 4: Plan Formulation Rancho Palos Verdes, California
Draft Feasibility Report
Chapter 4. Plan Formulation
This Chapter presents the plan formulation results from the Feasibility Study. It
presents the Formulation and Decision Making Process; Planning Objectives and Constraints,
Evaluation and Design Criteria; Alternative Measures considered to meet the Objectives;
Alternative Plans and the Evaluation of the Alternatives; and finally the Selection of the
Recommended Plan.
Plan Formulation and Decision-Making Process
Federal Government involvement in environmental quality, which would include
ecosystem restoration is supported in law, Executive Order, and treaty. A number of these
general statements can be found in the Fish and Wildlife Coordination Act of 1958; the Federal
Water Project Recreation Act of 1965 (as amended); the National Environmental Policy Act of
1969 (NEPA) (as amended); the Coastal Zone Management Act of 1972 (as amended); the
Water Pollution Control Act of 1972 (as amended); the Endangered Species Act of 1973 (as
amended); the Water Resources Development Acts of 1986, 1988, 1990, 1992, and 1996;the
Coastal Wetlands Planning, Protection, and the Restoration Act of 1990. These laws; and
other Federal laws and policies, all declare it national policy that full consideration be given to
the opportunities which projects afford to ecological resources. Section 306 of the 1990 Water
Resources Development Act authorizes the Secretary of the Army to include environmental
protection as one of the primary missions-of the U.S.Army CorpsofEngineers. -
In accordance with Corps of Engineers regulations, the general guidance in the
Economic and Environmental Principles and Guidelines for Water and Related Land
Resources Implementation Studies(P&G) adopted by the Water Resources Council in 1983,
applies to ecosystem restoration activities and will be used in formulating and evaluating
ecosystem restoration projects. The Federal objective in water resources planning is to
contribute to National Economic Development(NED) in order to alleviate problems and/or
realize opportunities related to water and related land resources, consistent with protecting the
Nation's environment.
The P&G allow for formulation of alternative plans which reduce net NED benefits in
order to address other Federal, State, local and international concerns not fully addressed by
the NED plan. The P&G state that the NED Plan is to be selected unless the Secretary of the
Army grants an exception to selecting the NED Plan when there are overriding reasons for
selecting another plan. Such overriding reasons include Federal, State, tribal, local and
international concerns, as well as the provision of significant environmental outputs such as
ecosystem restoration.
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The Corps of Engineers CMI Works budget guidance assigns priority to the restoration
of ecosystems and associated ecological resources. Therefore, consistent with the analytical
framework established by the P&G, plans to address ecosystem restoration should be
formulated based on their monetary and non-monetary benefits. These measures do not need
to exhibit net NED benefits and should be viewed on the basis of non-monetary outputs
compatible with the P&G selection criteria.
Decision-Making Criteria
Decision making regarding selection of a Recommended Plan among alternative plans
and justification of recommendations for ecosystem restoration projects are based on
information from a combination of factors. The decision making process associated with
ecosystem restoration attempts to incorporate human needs and values with our best
understanding of the natural environment, recognizing a complex blend of social, economic,
political and scientific information. Both quantitative and qualitative information is used
including information about outputs, costs, significance, acceptability, completeness,
effectiveness, partnership context, and reasonableness of costs.
Outputs. An ecosystem restoration proposal must be justified on the basis of its
contribution to restoring the structure or function, or both, of a degraded ecosystem, when
considering the cost of the proposal. Ecosystem restoration projects are justified through
determination that the combined monetary and non-monetary benefits of the project are
greater than its monetary and non-monetary costs.
Cost Effectiveness and Incremental Cost Analyses. An ecosystem restoration plan
should represent a cost effective means of addressing the restoration problem or Opportunity.
It should be determined that a plan's restoration outputs cannot be produced more cost
effectively by another alternative plan. Cost effectiveness analysis is performed to identify
least cost plans for producing alternative levels of environmental outputs expressed in non-
monetary terms. Incremental costs analyses identifies changes in costs for increasing levels of
environmental output. It is used to help assess whether it is worthwhile to incur additional costs
in order to gain increased environmental outputs.
Significance. An ecosystem restoration plan must make a significant contribution to
addressing the specified ecosystem problems or opportunities. Decisions concerning
significance would address (a) relevant importance of the environmental resources in terms of
institutional, public, and/or technical importance, (b) effects on the resources in terms of
differences between estimated future without-project and with- project conditions, and other
relevant information concerning duration, frequency, location, magnitude, and other
characteristics, such as reversibility, retrievability, and the relationships to long-term
productivity.
Acceptability.Acceptability is the workability and viability of the alternative plan with
respect to acceptance by state, tribal, and local entities. Public acceptance and compatibility
with existing laws, regulations, and public policies are also considered as part of acceptability.
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Completeness. Completeness is the extent to which a given plan provides and
accounts for all necessary investments or other actions needed to ensure the realization of the
planned ecosystem restoration outputs.
Effectiveness. Effectiveness is the extent to which an alternative ecosystem
restoration plan alleviates the specified problems and realizes the specified opportunities.
Proposed plans must restore important ecosystem structure or function to some meaningful
degree.
Partnership context. The cooperation between the Corps and one or more non-
Federal sponsors in sharing study and project costs, along with collaboration with any state,
tribal and Federal resource agencies or non-governmental entities is considered as part of
decision-making process.
Reasonableness of Costs. Alt-costs associated with a plan is considered to ascertain
that the costs are reasonable based on experience and judgement.
Systems of Accounts
The evaluation of the final alternative plans developed will include systems of accounts
displays that show the changes and tradeoffs between each plan with the No-Action Plan.
These displays will show changes related to the following accounts.
National Economic Development(NED)-will display the monetary costs and benefits
related to each alternative plan from a National Economic Development standpoint.
Environmental Quality(EQ)-will display the beneficial and adverse consequences on
each alternative as related to environmental and cultural resources, conditions and attributes.
Regional Economic Development(RED)-will display the beneficial and adverse
impacts related to regional economic development considerations such as employment,
growth of development, income, and other areas of interest.
Other Social Effects(OSE)-will display the beneficial and adverse impacts related to
public health and safety, community cohesion, recreation, and related matters.
Risk and Uncertainty
Plans and effects are examined to determine the uncertainty inherent in the data or
various assumptions of future economic, demographic, social, attitudinal, environmental, and
technological trends. When applicable, a limited number of reasonable alternative forecasts
that would, if realized, appreciably affect plan development and outputs should be considered.
For cases where the potential outcomes can be described in reasonablely well-known
probability distributions such as the probability of particular flood event, these probabilities
should be defined. Situations of uncertainty are those potential outcomes which cannot be
defined in objectively known probability distributions. Based on the study analysis, there are a
• number of areas of uncertainty that need to be addressed in the formulation process. These
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include: 1) The magnitude and rate of future landslide movements; 2) The effectiveness of
landslide stabilization measures if and when implemented by Non-Federal interests, and 3)
Other factors that may have a certain degree of uncertainty on which the findings and
conclusions of the formulation process will also be addressed in the final decision-making
process.
National Economic Development(NED) Plan
The alternative with the greatest net national economic development benefits shall be
designated as the NED Plan and recommended for Federal action, unless an exception is
granted by the Assistant Secretary of the Army for CMI Works, based on justification to
support a different alternative is in the Federal interest.
National Ecosystem Restoration (NER) Plan
The Corps of Engineers has extended and clarified the P&G by adding material
addressing single purpose and multiple purpose ecosystem restoration planning and decision
making. Extensions have been made to address the following:
1. Ecosystem restoration contributes to national ecosystem restoration (NER). Single
purpose plans are developed and evaluate in terms of their net contributions to NER. That plan
making the maximum contribution to net NER is designated the NER plan, and the NER plan
will usually be the Recommended Plan;
2. Multiple purpose plans which include ecosystem restoration contribute to both NED
and NER. Multiple purpose plans including ecosystem restoration are developed and
evaluated so that an optimum tradeoff plan maximizing the sum of the net contributions to
NED and NER is designated, and usually recommended, and
3. Positive and adverse effects of ecosystem restoration plans are displayed in the EQ
account as separate entries.
Locally-Preferred Plan
In some cases where the Non-Federal Sponsor prefers an alternative that is more
costly than the NED Plan, and the increased development is not sufficient to warrant full
Federal participation, the Sponsor will be required to pay the difference in cost between the
NED Plan and the locally-preferred plan.
Planning Objectives and Constraints
The specific planning objectives for the Feasibility Study were established based on
reviews of the Congressional authorization language; reviews of the decisions made during the
completed Reconnaissance Study; analyses of the problems and needs described in Chapter
3; and considerations of agency and public views and desires resulting from public
involvement activities.
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The Feasibility Study authorities call for investigating erosion stabilization for the
purposes of contributing to the stabilization of the Portuguese Bend landslide and adjacent
areas (Section 712 of Water Resources Development Act of 1996) and to investigate
measures to conserve fish and wildlife, (Section 116(c) of Water Resources Development Act
of 1990). The decisions made on the Reconnaissance Study indicated that Federal
participation in landslide stabilization measures are not within the purview of the Corps of
Engineers, eliminating further consideration of Federal improvements for landslide
stabilization. There are, however, numerous authorities under which the Corps of Engineers
can participate in environmental restoration improvements, as indicated above.
Coordination with Federal, State, and local agencies concerned with fish and wildlife
conservation notes that from a marine benthic standpoint, the vast majority of shallow marine
substrates in southern California are unconsolidated sand or mud (as much as 95% by an
MBC 1988 estimate), soft bottom habitat is not a unique habitat-type in the Study Area. Natural
hard rocky reef, however, is an extremely rare, productive, and valuable habitat-type. Natural
hard rock habitat is so rare and valuable that California Department of Fish and Game's
(CDF&G) Marine Resources Divisions has a program to create and improve artificial reef
habitat to augment the scarce natural reefs. As natural rocky reef habitat is so rare and
supports a large, diverse assemblage of marine plants and animals, any effort to restore
damaged or degraded natural reef habitat would be extremely beneficial to the marine
biological community and is of great interest to resource agencies such as CDF&G and
National Marine Fisheries Service (NMFS).
At an April 26, 1995 public information/environmental scoping meeting, many interests
supported the need to restore the environmental conditions along the City of Rancho Palos
Verdes coastline. Concerns expressed related to whether this can be accomplished without
stabilization of the landslide, the potential costs for restoration, and the potential for any plans
causing other impacts.
Finally, the habitat evaluation analysis performed in Chapter 3 indicates that the habitat
values along Portuguese Bend have been severely degraded historically, and are substantially
less than the value along surrounding areas. The efforts to restore kelp forests in the
Portuguese Bend area have not been successful primarily due to the continued sediment
deposition and turbidity caused by the landslide.
Based on the foregoing, the specific planning objectives established for the study are:
1. Restore the rocky subtidal habitat and associate kelp forest ecosystem along the
Portuguese Bend coastal area, and
2. Reduce turbidity that is degrading kelp forest habitat along the downcoast areas of
Portuguese Bend to the vicinity of Whites Point.
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Planning Constraints
Planning Constraints are those factors that must be considered in the planning process
that must be recognized and could limit the formulation of alternative plans. For the Rancho
Palos Verdes Feasibility Study, the list of constraints considered in the formulation of
alternative plans are:
1. Measures and plans should not increase the risk of aggravating the landslide
conditions along Portuguese Bend and adjacent areas.
2. Water quality conditions in the Study Area should not be further degraded as a
result of any of the plans in accordance with the Clean Water Act of 1972, as amended.
3. Measures and plans should be in conformance with air quality requirements adopted
for the South Coast Air Basin.
4. Measures and plans should not result in any adverse impacts to Federal and State
threatened and endangered species.
Design Considerations
Major considerations in identifying, selecting, and developing measures and plans to
meet the stated planning objectives included: 1) examining the cause(s) of the degradation of
the Portuguese Bend and adjacent area ecology, 2) the need to avoid impacts that could
possibly aggravate the landslide conditions, and 3) to consider the impacts of continued .
movement of the landslide on ecological restoration measures and plans.
Causes of Degradation
The potential cause of the degradation of the kelp forests that thrived in the Portuguese
bend area have been analyzed by many interests as discussed in Chapter 3 and in the Draft
EIS/EIR. These include sediment deposition covering the rocky benthic needed for
establishment of kelp, and variations in the water temperature and quality conditions. As
indicated in Chapter 3, warmwater conditions from 1957 to 1959 caused a substantial loss of
kelp forests in the Southern California area.
Although some areas did recover, the Palos Verdes Peninsula remained generally
degraded for some time. During this period, several factors may have impacted on the
recovery effort, including significant sediment deposition and turbidity from the Portuguese
Bend and adjacent landslides, water and sediment chemical contamination from Whites Point
outfall, and increases in the frequency of major storms causing scouring of kelp beds.
In the 1970s, several efforts to restore Palos Verdes Peninsula kelp forests, including
areas along and upcoast of Abalone Cove, and downcoast of Portuguese Bend, were found to
be successful. The success of this restoration can be attributed to stabilization of the Abalone
Cove landslide, deflection of Whites Point Outfall towards deeper areas, as well as
improvements in water and sediment quality along these restored areas. Based on the
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.40 success of the restoration efforts in many areas along the Palos Verdes Peninsula, which
experience similar impacts from the Whites Point Outfall and effects of storms, water
temperature, and water and sediment quality, it can be concluded that the primary remaining
reason that limits the restoration of kelp forests in the Portuguese Bend area is related to
sediment deposition and turbidity from the landslide.
This rationale appears to be further supported based on experiences in early 1990s
when the City of Rancho Palos Verdes constructed gabions along the shore to reduce erosion
of the bluff. During the limited time that the gabions were in place, there were many
observations of kelp beginning to reestablish in the area where the gabions reduced erosion,
allowed for scouring of sediment deposits and reduced turbidity. Unfortunately, the gabions
were quickly destroyed by landslide movement and storm waves.
Accordingly, the measures and plans for the ecological restoration along Portuguese
Bend focuses on removal and control of sediment deposition that is covering the rocky
environment, and reducing turbidity.
Measures that Could Impact the Landslide
The geologic mechanism causing the Portuguese Bend landslide is extremely
complex. As described in Chapter 2, geologists, who investigated landslide problems along
Portuguese Bend and adjacent areas, have indicated that the continued landslide movement
appears to be directly related to: 1)the benthic layers associated with Portuguese Tuff, 2)
groundwater and drainage impacts on the benthic layers, 3) unstable steep grades and effects
of saturated soil on increasing the landslide driving force, and 4) continued erosion of the
coastal bluff created from landslide material which is reducing any counterforce to the
landslide driving force at the toe of the slide.
Corps of Engineers geologists have reviewed many reports and investigation results
related to the landslide. Their conclusions at this time based on available information is that
because of the complexity of the landslide, there is a high degree of uncertainty on whether
the landslide could be stabilized without major actions to address many of the causes noted
above. Further, there is concern that any measures taken to restore the environment such as
removal of material from the shorefront bluff or other grading that might impact any
counterforce created by the bluff should be avoided.
Accordingly, any measures for restoring the environment to remove sediment deposits
and control erosion of the bluff, must not aggravate the apparent causes of the landslide.
However, it must be recognized that the City of Rancho Palos Verdes in implementing
their stabilization plan appear to have had some success in stabilizing or slowing the landslide
movement, in particular at Abalone Cove and Klondike Canyon. In addition, landslide
movement appears to be reduced in many areas of the landslide and subslides. In this regard,
it may be possible that the continued efforts of the City to stabilize the Portuguese Bend
landslide may be successful in the future, although there is a major degree of uncertainty in
being able to assure this will happen at this time. In general, any determination that the
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landslide is stable will require continued monitoring of landslide movements, and careful
avoidance of measures that could impact on the landslide causes.
Measures Impacted by the Landslide
Chapter 2 presents information historic and present landslide movements and also
information on the location of the landslide plane and the toe of the landslide plane. Additional
information is presented in the Geotechnical Appendix. This data indicates that there is some
possibility that the present landslide toe may be located near the present shoreline, out to
about 100-to-100 feet. Landslide measurements and borings taken by the City as part of this
study confirm movement along the shoreline. However, recent measurements of newly
installed GPS monuments appear to indicate little or no movement along some sections of the
shoreline, with continued movement along two other sections. These monuments have been
installed and measured recently, and it is too early to determine whether this information can
be used to further determine the location of the toe of the slide plane.
The design concern related to the continued movement of the slide and the location of
the slide plane toe is to avoid constructing measures that would be destroyed or require major
repairs and replacement because of damage from either movement of the foundation or being
overrun by debris moving along the slide plane. In this regard, the side-scan sonar and seismic
studies appear to show stable foundation about 400 feet offshore at about elevation-18 feet
MLLW—this is the shoreward limit of the Study Area. It should also be noted that the analysis
of historic shorelines shows the slide shoreline extending about 200 feet seaward of the
existing shoreline, but has since eroded back to the current location. At this time, there is no
information between the present shoreline and the-18 foot isobath that reveals more 4
specifically the location of the slideplane toe. However, there is some possibility that the toe
could be as dose as the shoreline along some reaches and out to about 100 to 200 feet
offshore of the existing shoreline.
Based on this analysis,a design criteria adopted for the Feasibility Study was to avoid
measures and designs that could be severely impacted by continued slide movement. The rate
of movement considered in this report for design purposes was based on long term historic
movement rates or an average annual rate of 7.6 feet for the entire shoreline.
Initial Screening of Management Measures
The management measures examined include those measures that could remove
sediment deposits from the Portuguese Bend area, control erosion of the bluff and future
sediment deposition; and reduce turbidity. The initial screening of the identified measures
considered the design considerations noted above as part of the initial screening. A summary
of the initial screening, including an evaluation of the measure and whether it is considered
viable to be considered in developing plans, is presented in Table 4-1.
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410 Table 4-1. Initial Screening of Management Measures
Management Measure Evaluation Viable '
Dredging Sediment Effective to restore rocky bottom Yes
Deposits habitat conditions
Remove Landslide Bluff Could aggravate landslide by No
from Wave Runup reducing counterforce.
Revetment along Bluff Frequently damaged by landslide No
movement
Gabions Frequently damaged by landslide No
movement
Flexible Revetment Frequently damaged by landslide No
movement
Breakwater Cannot control sediment from No
continuing to move
downcoast
Containment Dike Contains erosion and sediment Yes
within dike area
Cobble Protective Frequently damaged by landslide No
Beach movement and storm waves
Seawall Frequently damaged by landslide No
Groins Cannot control offshore sediment No
movement
Natural Scouring of If erosion is controlled and Yes
Sediment Deposits sediment from the bluff
contained it is viable
Alternative Plans Considered
Alternative plans were developed using the management measures identified above
that were found to be viable. The alternatives developed involve constructing containment
dikes in combination with either natural scouring of sediment deposits or dredging deposits to
accelerate restoration.
Basis for Design
In this section, some of the design considerations used in developing each alternative
plan. Three locations were considered in developing the three alternatives. The first alternative
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would locate the containment dike at about-12 feet, MLLW, about 200 feet offshore. This
location was selected based on trying to locate the dike as close to the shore as possible,
without being impacted by historic shoreline location, which was about 200 feet offshore.
The second alternative located the dike in about -18 feet, MLLW, about 400 feet
offshore. This location was selected based on information from geotechnical studies that was
able to confirm sound foundation conditions and from historic records on shoreline
advancement which indicate that based on average landslide movement the landslide is not
likely to reach the dike over the 50-year project life.
The third alternative dike location considered was to locate the dike at about-6 feet,
MLLW or about 50 feet offshore. This alternative was developed to determine if the first costs
and repair and maintenance costs at this location could be more cost effective than the other
alternatives. Details of the design of each alternative are presented in the Coastal Design
Appendix.
Functional Design -Erosion Control
Each alternative plan was designed to minimize the erosion of landslide generated
sediment. The plan provides a containment dike that is attached to stable areas of land that
surrounds the landslide. The structure will retain landslide sediment in two ways. First the
structure will reduce erosion of the landslide bluff toe by significantly decreasing transmitted
wave energy that erodes the material. Second, the water region located between the structure
and the landslide will act as a settling basin. Most of the sediment that is input from the
landslide into this basin will settle on the bottom. Fine material that does remain suspended will 411.
have difficulty transmitting through the structure as its core will act as filter. It is expected that
during extreme events, more of the fines will be transmitted through the structure, but this is
not expected to be a significant impact to the environment, as turbidity levels are normally
elevated during these events anyway.
Functional Design -Natural Sediment Deposit Removal
Seaward of the containment dikes, natural processes will scour sediment deposited on
the reef habitat in the nearshore zone once the supply of material from the landslide is stopped
by the dike structures. This sediment can be suspended by nearshore waves and transported
down coast via longshore current.
Bedrock Uncovering Rates. Dan Pundella of the Vantuna Research Group, visually
observed sediment cover conditions for the region located between Bunker Point and Whites
Point. Mr. Pundella indicated that approximately 25% of the rocky reef habitat located in this
region between MLLW and-30 feet MLLW was covered with sand. The same sediment
thickness contours that exist in Portuguese Bend area are assumed for this area. From the
sediment thickness contour and erosion rates, time and acreage of recovered habitat, for with
project conditions, can be calculated.
Table 4-2 shows the calculation for exposure of rocky bottom habitat. The-10 to-20 ft
region of Area 1 shown on Figure 6.3 will be exposed in 14 years. The-10 to-20 ft region of
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1111 Area 3 will be exposed in 11 years. The-20 to-30 ft region of Areas 1 and 3 will be exposed in
87 and 53 years, respectively, while the-20 to-30 ft region of Area 2 will be exposed in nine
years. Areas at depths extending from-30 ft MLLW to-90 ft MLLW is not expected to be
uncovered. Based on this analysis it is not expected that local sea and swell will scour sandy
material deeper than-90 ft MLLW.
Table 4-2. Rate of Uncovering Rock Substrate
Reach Depth Surface Avg Sed Scour Time to
(Station to Range Area Thick Volume Rate Uncover
Station) (ft to ft) (ft^2) (ft) (cy) (cylyr) (Yrs)
-7+05 to 27+53 -10 to-20 1,007,837 2.5 93,318 6,514 14.3
80+45 to 173+48 -10 to-20 3,053,625 2.5 70,686 6,514 10.9
27+53 to 43+56 -20 to-30 458,872 2.0 33,991 3,832 8.9',
-7+05 to 27+53 -20 to-30 1,204,652 7.5 334,626 3,832 87.3
80+45 to 173+48 -20 to-30 2.900.123 7.5 201.397 3.832 52.6
Functional Design -Dredging Sediment Removal
An alternative to removing sediment by natural scouring is to remove sediment deposits
by dredging, which will accelerate the ecological restoration in the Portuguese Bend Cove
area. The dredging of sediment deposits would involve removing sediment from hard rock
habitat in Areas 2 and 3, as shown on Figure 4-1. Dredging from Area 5 is not proposed
because of potential impacts to existing kelp.
Functional Design -Turbidity Reduction
Turbidity is expected to be reduced to the normal (pre-slide) level once a dike
alternative plan is constructed. This is due to the fact that the crest of the core in the structures
is at+6 feet MLLW, preventing significant energy transmission. The reduction in local sea and
swell wave energy behind the dikes will be significantly reduced, so erosion of the landslide
and hence associated turbidity will be drastically reduced.
Structural Design. The design of the dike structures is consistent with design of
breakwater structures as prescribed by the Corps of Engineers Shore Protection Manual
(SPM). Crest elevations for each alternative are designed to minimize overtopping of the
structure, and range up to +24 feet, MLLW. Core elevations and structure thickness are
designed to minimize wave transmission that could allow for continued erosion of the bluff.
The stone sizes are based on sizes needed to maintain a stable structure using SPM methods
and can range up to 17 tons for armor stone for certain sections of the structure. The
structures will be tied into land areas on Inspiration Point and at the eastern end between the
• landslide and existing drainage, which appears to be historically stable.
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Construction Requirements. The alternative plans can be constructed using a land-
based or combination land and water-based operation. A land-based operation would include
truck mounted cranes, loaders and/or dozers, and many rock trucks. The stone would be
transported to the site by truck. Stockpiling would occur with the use of a loader or dozer.
Placement would occur with a crane, excavator, dozer, or loader.
A combination land and water-based operation would involve placing stone using a
crane mounted on a derrick barge, a rock barge, and the previously described land-based
operation. Tug boats would be used to tow in the rock barge and position the derrick barge.
The dredging of sediment deposits could be accomplished with a hydraulic dredge,
hopper dredge or clamshell barge. Disposal of the material would be at LA-2.
Maintenance Requirements. The design of the alternatives are based on the
assumption that the landslide will continue to move seaward at an average annual rate of 7.6
feet per year. At this rate, the landslide toe is expected to reach the Alternative 1 dike in about
20 years, at which time material behind will need to be removed to avoid major damage to the
dike structure. For this plan, it is estimated that 3,000,000 cubic yards will need to be removed
every 20 years. For Alternative 2, material from the landslide would not reach the structure until
after the 50-year economic life of this project. At that time, continued functioning of the
structure without damage from the landslide would require removal of about 7,000,000 cubic
yards.
For Alternative 3, the continuous movement of the landslide is expected to cause
damage to about 30%-to-50% of the structure every year. In addition, material encroaching on
the structure will need to be removed, estimated at 730,000 cubic yards every five years.
Methods for removing material from behind the dike include dredging and using a
conveyor belt to load barges for disposal at LA-2, or perhaps as a cap on the Santa Monica
Bay Contaminated Benthic site. A second method would be to truck the material to barges at
Los Angeles or Long Beach Harbor for disposal at LA-2, or perhaps as a cap. If the project is
implemented consideration would need to be given to potential beneficial uses of the material
at that time, as well as other available dredge material disposal options.
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• • •
1 47 , semen es
1 p.,,„,.. •ten AREA 1
• Il rrl,. 4`.1.ono
MAJOR CONTOURS AT 10 FOOT INTERVALS
•+ `,I 4...
�4)
AREA 4 —•—•—•—. ::::EH
SEDIMENT THICKNESS CONTOUR (DILL
�1
OLOCENE SEDIMENTTHICKNESS 0
C
POTENTIAL HARD BOTTOM RECOVERY AREA 0
1 •P
AREA 3 • tt -'
4 .s` �` 4 a
i ,:,:;,. AREA 5 Fig.s l 3
t' .... .• Sediment thicimeas
" •. over bedrock 3
�,' and areas of e!
'` potential restoration. s
•
5.
.v Am a IIiY MR t \. e ' to
sovIE. 1"._MO'
NOTES "'" ••
sss� aa.
1. HOLOCENE SEDIMENT THICKNESS OVER BEDROCK '�---`amu
(CONTOUR INTERVAL 8 FT) . SOURCE. R.F. DILL ET AL. 1998 maims
2. CORPS' 07-95 HYORO SURVEY CONTOURS AT 10 FT INTERVALS. Areal-Area behind dike =L.
3. LAND CONTOURS FROM 08-95 AERIAL SURVEY Al 10 FT INTERVALS. Area 2-Nearshore area between-10 and-30 B1LLW 11,11010LOIN oan�cavrrr. l'ALiiOWl a
SUPPLIED BY THE CI TY OF RPV. Area 3-Nearihore area between-20 and-30 MLLW SEDIMENT THICKNESS
Area 4-Bunker Point Reef-eiisting kelp bed
Arts 5-Bunker Pt.to Whiten Pt Ares-existing ill
kelp bed with sediment covering
approx.% of the ares
Descriptions of Alternative Plans
11114
The following presents brief descriptions of the alternatives developed using the above
design, construction and maintenance considerations. Details are presented in the Design
Appendix.
No-Action Alternative
The No-Action Alternative involves no major action to meet the planning objectives.
Under this condition, the landslide is expected to continue to move at a rate of 7.6 feet per
year and contribute 146,000 cubic yards of material annually. At this rate, more than 7,000,000
cubic yards of material will be added to the littoral cell. Negative impacts to the marine
environment will continue as sedimentation gets deeper and covers more rocky habitat.
Additionally, the sustained turbidity will continue to negatively impact the kelp communities.
The City of Rancho Palos Verdes will most likely continue attempting to stabilize the
landslide.
Alternative 9 —Dike 200 Feet Offshore
This alternative involves the construction of a 2,520-foot-long dike located 200 feet
seaward of the existing bluff toe which "surrounds"the Portuguese Bend slide area, as
illustrated on Figure 4-2. The maximum crest elevation is+21 feet MLLW. The dike is
designed with a core elevation of+6 feet MLLW to retain sediment to the Mean Higher High
Water(MHHW)tide level. The stone gradation and quantity, armor stone crest widths and
thickness of typical cross-sections of the dike are shown on Figure 4-3.
Alternative 1 will rely on natural scouring for removal of sediment deposits to restore
rocky habitat, while Alternative 1A includes dredging of about 460,000 cubic yards of material
to accelerate restoration.
Construction
Rock for the dike would be delivered to the site by a barge from Catalina Island. Rock
placement for the dike would be ocean-based on a floating barge with a crane except from
stations 0+00 to 5+00. Land-based construction is expected for this portion of the dike.
Construction would progress from close to shore then move seaward. Armor stone would be
keyed into position such that the long axis of the stone is perpendicular to the face and center
line of the dike.
For the ocean-based operation, it is assumed that the-10 foot depth is adequate for
barge operations without compromising the barge's loading capacity. No excavation is
4-14
• expected to be required except for the area between stations 0+00 and 5+00 and near station
27+70.
Dredging of sediment deposits will be by either hydraulic pipeline, hopper, or clamshell
dredges with material disposed at LA-2.
Maintenance
Maintenance requirements for this alternative include removing material to prevent the
landslide from encroaching on the structure and periodic repair of the dike caused by
foundation instability and as a result of major storm events. The landslide material is expected
to continue sliding at a rate of 7.6 feet per year. At this rate, it is estimated that the slide front
will reach the dike in 26 years. Consequently, the alternative calls for removal of material
before the slide reaches within 50 feet of the dike structure. This will require removal of about
3,000,000 cubic yards"every 20 years. Material will be dredged from behind the dike and
barged to LA-2.
There is uncertainty regarding the foundation conditions located 200 feet offshore of
the current bluff location because of limited information. Investigations appear to indicate that
the slide toe is located somewhere between the current location and 200 feet offshore.
Because of this uncertainty, there is some probability that the dike may require repair as a
• result of foundation movement. To account for this probability, it is estimated that 25%of the
dike structure may require repair about 25 years after construction.
In addition to the possibility of unstable foundation conditions, it is likely that the
structure could require repairs after major storm events. Wave action during the storm could
cause rolling or other stone movement requiring repair of the dike to maintain stability of the
structure.
•
4-15
Dq y
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zi
` PORTUGUESE SENO LANGSL10E •A
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PLANS ALTERNATIVE 1 •10 �Y'_ ids
1 Ams
NOTES. 100' 0 500' % w ...KA.TIVI i.w WS FT M.Ta
I. HYDRO CONTOURS BASED ON JULY 1995 USAGE HYDRO SURVEY -20 R'"• T"•I'A•Axamod
2. LAND CONTOURS BASED ON AUG 1995 AERIAL PHOTOGRAMETRY SCALE "'S^
•
3. SOUNDINGS ARE GIVEN IN FEET MLLV 6...•n rr •' .a"
:• 0 9.:
• Figure 4-3. Alternative 1 Cross-Section
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4-17
•
Alternative 2— Containment Dike -400 Feet Offshore
This alternative is similar to Alternative 1, except that the dike would be 400 feet
seaward from the existing bluff toe; it also "surrounds" the Portuguese Bend slide area. Its
maximum crest elevation is +24 ft. MLLW. Alternative 2's features are displayed on Figure 4-4
and Figure 4-5.
Alternative 2 will rely on natural scouring for removal of sediment deposits to restore
rocky habitat, while Alternative 2A includes dredging of about 420,000 cubic yards of material
to accelerate restoration.
Construction
Construction would be the same as described for Alternatives 1 and 1A, except that it
requires about 30% more rock material, and would reduce dredging requirements to remove
sediment deposits to 420,000 cubic yards.
Maintenance
Alternative 2 maintenance requirements during the 50 year economic life is expected to
include repairs as a result of wave action during major storm events. The foundation conditions
located about 400 feet are expected to be stable based on review of geologic data developed
during this and other studies as presented in the Geotechnical Appendix. Therefore, no repairs
are expected to be required for Plans 2 or 2A due to possible unstable foundations.
With the slide movement of seven feet per year, the landslide is not expected to
impact the containment dike for 50 years. At that time, about 7,000,000 cubic yards will require
removal by the City of Rancho Palos Verdes to extend the project life by 50 years.
111
4-18
•
• •
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PLANT ALTERNATIVE 2 +• fI" • 0
0
NOTES: 100' 0 5500' ; ws aMea:i.t I.On.n El 1ro1 TOE
I. HYDRO CONTOURS BASED ON JULY 1995 USACE HYDRO SURVEY I -20 �•'• R""•cwnnir•r�'r�INT
,
2. LAND CONTOURS BASED ON AUG 1995 AERIAL PHOTOGRANETRY SCALE r..—.. I
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3. SOUNDINGS ARE GIVEN IN FEET MLLM "'rs,;,:,- �• s. "'0'"'�•
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•
Alternative 3—Containment Dike 50 Feet Offshore
Alternative 3 involves the construction of a 2,450-foot-long dike located 50 feet
seaward of the existing bluff toe, surrounding the Portuguese Bend slide area, as shown on
Figure 4-6. The maximum crest elevation is +13 feet MLLW. The stone gradation and quantity,
armor stone crest widths and thickness of typical cross-sections of the dike are shown in
Figure 4-7.
Alternative 3 will rely on natural scouring for removal of sediment deposits to restore
rocky habitat, while Alternative 3A includes dredging of about 480,000 cubic yards of material
to accelerate restoration.
Construction
Construction would be similar to Alternatives 1 and 2, except for a substantial reduction
in rock material, with minor increases in dredging to uncover the rocky habitat.
Maintenance
• Major repairs to about 30% to 50% of the structure is expected each year, as a result of
expected foundation movement along the active landslide toe. In addition, about 730,000 cubic
yards of material will require removal every five years to prevent the landslide from
encroaching on the structure.
Monitoring and Adaptation
All three plans include a requirement for monitoring recovery of kelp forest ecosystem
and taking additional actions if necessary to promote recovery. The monitoring program
includes surveys for a period of five years to review environmental conditions in the recovery
area including turbidity levels, uncovering of buried areas, recovery results of kelp forest, and
associated species recovery After the first three years, actions may be taken to seed and plant
kelp to help generate recovery. Monitoring and adaptation will be conducted in coordination
with Fish and Wildlife Service, and National Marine Fisheries, and to the extent possible be
incorporated into the California State Fish and Games Kelp Management Program. Additional
information on the Monitoring and Adaptation Plan is presented in the Draft Environmental
Impact Statement and Environmental Impact Report.
4-21
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PLAN' ALTERNATIVE 3
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HYORO CONTOURS BASED UN JULY 1990 USACE HYDRO SURVEY eESilini.r.---- ""'---- 1 ,-20 !--ii.".7i77 N.M.=MIK De.foXITIMIXT
LAND CONTOURS RASE0 ON AUU 1995 AERIAL PHOTOGRAHETAY SCALE I. ',Ts
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STA 1.00 TO STA 6.65 1
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TYPICAL SlCrlon Si VI
STA 1.94 TO STA 70.67 (/)
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TYPICAL SICIIOK C•C
STA I0•67 TO STA 23.02
ATS
rf_ .. ,
Alternative Plan Costs
III*.
:.
First Cost
The estimated first cost of constructing each alternative, associated average annual
operation, and maintenance costs are displayed in Table 4-3. The cost estimates are based on
detailed analysis of construction requirements, including materials, equipment, and labor. The
first cost also includes costs for real estate requirements; the five year program for monitoring
and adaptation; preconstruction engineering and design, engineering during construction, and
construction management. Maintenance costs for each alternative are based on costs for
repairing breakwater structures, recognizing potential structural damage during severe storm
events, and periodic dredging necessary to avoid landslide encroachment on the dike
structure.
Real Estate Requirements
Real estate required for each alternative plan includes the required lands needed to tie
in the easterly section of the dikes, and staging areas for construction activities and a haul
road. In general, these lands are located on lands that are either impacted by the landslide or
are subject to erosion. Consequently, there is very limited value to these lands. Real estate
cost details are included in the Real Estate Appendix.
0
Table 4-3. First Costs of the Environmental Restoration Alternatives
(October 2000 Price Levels)
Construction Costs I Plan 1 I Plan 1a I Plan 2 Plan 2a I Plan 3 Plan 3a
Dike $17,140,000 $17,140,000 $23,537,000 $23,537,000 $5,604,000 $5,604,000
Dredging 0 $3,730,000 0 $3,591,000 0 $3,805,000
Total Construction $17,140,000 $20,870,000 $23,537,000 $27,128,000 $5,604,000 $9,409,000
Costs
Planning, Engmg, $1,371,000 $1,669,000 $1,883,000 $2,170,000 $1,150,000 $1,454,000
and Design Costs
Construction Mgmt. $1,111,000 $1,335,000 $1,525,000 $1,740,000 $363,000 $591,000
Costs
Monitoring and $460,000 $460,000 $460,000 $460,000 $460,000 $460,000
Adaptation Plan
Real Estate Costs $35,000 $35,000 $35,000 $35,000 $35.000 $35.000
I Total First Cost $20,117,000 I $24,369,000 $27,440,000 I $31,533,000 I $7,612,000 I $11,949,000
4-24
ip
• Average Annual Costs
•
The average annual costs for each of the alternatives are presented in Table 4-4. The
average annual cost includes interest and amortization on the First Cost over a 50-year
economic life at a 6-5/8% interest rate. The costs also includes estimates for Operation,
Maintenance, Repair, Replacements, and Rehabilitation (OMRR&R) of plan features as
discussed above.
Table 4-4. Average Annual Costs of Alternative Plans
Annual Costs
Alternative Interest& Dike Dike Maintenance
Amortization Maintenance''-' Repair ti Dredging—I' Total
1 $1,481,000 $85,700 $69,400 $747,900 $2,384,000
1a $1,794,000 $85,700 $69,400 $747,900 $2,697,000
2 $2,020,100 $117,700 0 0 $2,137,800
2a $2,321,400 $117,700 0 0 $2,439,100
• 3 $560,400 $28,000 $2,600,000 $1,401,600 $4,590,000
3a $879,700 $28,000 $2,600,000 $1,401,600 $4,909,300
1/Dike repairs due to storm and wave action(0.5%construction cost)
2/Dike repairs due to possible unstable foundations
3/Material removal to avoid landslide encroachment on dike
Environmental Effects of Alternative Plans
Dill and Nordall, in 1995, found that sediment thickness is less than five feet in most of
the nearshore area. However, Sadd and Davis (1997, Appendix B) reported that sediment is, in
general, less than a meter(3.3 feet) thick as far out as the 25-foot isobath.
When the rocky habitat is exposed, this hard bottom surface would be re-colonized by
marine plant and animal life similar to that occurring upcoast in the unaffected areas of Palos
Verdes Point. An additional benefit likely to occur is reduced turbidity to the downcoast
beaches. The negative effect of sedimentation on kelp forest is discussed in detail in Foster
and Schiel [1985:10].
.•
4-25
Assumptions that the underlaying hard rock might be re-exposed and re-colonized by
giant kelp are supported by several facts. First, sediment covering the nearshore area is
unconsolidated material and no cementation or unusual compaction was reported from
sediment surveys (Sadd and Davis 1997:9). Secondly, several studies report that wave-
generated currents are actively eroding landslide-generated sediment that is deposited into
Portuguese Bend from the nearshore to offshore and down coast areas (Drake et al. 1994:8;
Kayen et al. 1994:8; Sadd and Davis 1997:12). Thirdly, a 744-foot-long, tiered gabion structure
constructed in 1988 (and later lengthened to 2,100 feet) by the City of Rancho Palos Verdes in
Portuguese Bend was reported to have reduced sedimentation and turbidity in the immediate
nearshore area and resulted in the development of a lone kelp stand in the area (See USACE
1992:15 and Stephens 1990: page C-2-18). Finally, giant kelp is reported to occur in
Portuguese Bend in areas when sedimentation is relatively thin or where hard bottom is
repeatedly uncovered (Appendix A:15 and 55).
Within the dike, it is assumed that all existing marine life would eventually be smothered
by the increasing sediment load.
In summary, Area 2 consists of approximately 26 to 37 acres (depending of the action
alternative) of nearshore area that is within the-30-foot isobath and covered with five feet or
less of sediment. Based on the above assumptions, it is predicted that the natural hard rock
habitat of Area 2 would become uncovered and restored if sedimentation could be contained
within the dikes. It is expected that the existing soft bottom habitat, which is impacted by
frequent deposition of eroded sediment, would be restored to high quality hard bottom habitat.
It is expected that marine plants,especially giant kelp, and animals will re-colonize the hard
rock reef and cobble beds. The reestablished kelp forest is expected to support a full
complement of marine animals common to a kelp forest.
Reduced Turbidity
The turbidity plume and its associated water column impacts are presumed to extend at
least to the 30-foot isobath from Portuguese Bend to Whites Point. As shown on Figure 4-8,
the area of impact includes the 125-acre "Area 4" reef area at Bunker Point, which is largely
exposed and sediment free; and the nearshore Area 5 area from Bunker Point to Whites Point,
with approximately 150 acres.
The impacts of turbidity, such as decreased light penetration, on marine plants,
especially giant kelp, is discussed in detail in Forster and Schiel (1985:12). Because marine
plants depend on light for photosynthesis, turbid waters inhibits plant growth which in turn limits
the marine animals that feed on the plants. The marine biological community, therefore, is
expected to benefit from improved water clarity as turbidity is reduced. Specifically, Areas_4 and
5 are expected to benefit from improved water clarity in the nearshore environment.
The proposed environmental restoration alternatives involve the construction of an
offshore dike which is designed to contain landslide-generated sediment and turbidity. Hard
•
4-26
• rock reef is expected to be uncovered naturally or mechanically and be re-colonized by marine
plants and animals. The time necessary for the rocky reefs to uncover naturally is presented in
Table 4-2. Additionally, the quality of existing kelp beds impacted by near-constant turbidity is
expected to be improved.
Tables 4-5, 4-6, 4-7 and 4-8 summarize the Average Annual Habitat Units expected to
be generated as a result of the proposed restoration alternatives over the 50-year project lives
of Alternatives 1, 1A, 2, and 2A. The methods used in estimating the habitat values are
explained in Chapter 3 and further described in Appendix C of the Draft EIS/EIR. The
differences in habitat values between Alternatives 1 and 2 is the result of the larger area lost
behind the offshore dike. The benefits to areas outside of the dike are the same, however. The
benefits for Alternative 3 were not analyzed in detail because of the uncertainty related to the
engineering soundness of this Alternative. However, it is expected that the potential increases
in Average Annual Habitat Units would be similar to Alternative 1.
Table 4-5. Habitat Values in the Study Area
Alternative 1
• Location AAUUs
Portuguese Bend- behind the dike +0.1
Portuguese Bend (-10 to -20') +18.5
Portuguese Bend (-20 to-30') +4.2
Portuguese Bend-Area 3 +9.6
Bunker Point(Area 4)
+161.9
Bunker Pt-Whites Pt. (-10 to-20') +15.7
Bunker Pt- Whites Pt. (-20 to-30') +6.6
Bunker Pt-Whites Pt- kelp bed +193.8
Total +410.4
4-27
Table 4-6. Habitat Values in the Study Area
.'
Alternative la
Location AAUUs
Portuguese Bend- behind the dike +0.1
Portuguese Bend (-10 to-20') +22.2
Portuguese Bend (-20 to -30') +27.0
Portuguese Bend-Area 3 +10.6
Bunker Point(Area 4) +161.9
Bunker Pt-Whites Pt. (-10 to-20') +15.7
Bunker Pt- Whites Pt. (-20 to-30') +6.6
Bunker Pt-Whites Pt.- kelp bed +193.8
Total +437.9
•:
Table 4-7. Habitat Values in the Study Area
Alternative 2
Location AAUUs
Portuguese Bend - behind the dike +0.1
Portuguese Bend (-10 to-20') +10.4
Portuguese Bend (-20 to-30') +4.2
Portuguese Bend -Area 3 +9.6
Bunker Point(Area 4) +161.9
Bunker Pt- Whites Pt. (-10 to-20') +15.7
Bunker Pt-Whites Pt. (-20 to -30') +6.6
Bunker Pt-Whites Pt.- kelp bed +193.8
Total 402.30
•
4-28
IMOTable 4-8. Habitat Values in the Study Area
Alternative 2a
Location AAUUs
Portuguese Bend- behind the dike +0.1
Portuguese Bend (-10 to-20') +12.5
Portuguese Bend (-20 to-30') +27.0
Portuguese Bend-Area 3 +10.6
Bunker Point(Area 4) +161.9
Bunker Pt-Whites Pt. (-10 to-20') +15.7
Bunker Pt-Whites Pt. (-20 to-30) +6.6
Bunker Pt-Whites Pt.-kelp bed +193.8
Total +428.2
The net gain in habitat units from the nearshore and offshore dikes are summarized in
Table 4-9. The loss of habitat behind either dike is expected to be offset by the restored habitat
value of the immediate Portuguese Bend area alone. When added to the additional benefits
expected from: 1) eliminating turbidity impacts at Bunker Point and the Bunker Point to Whites
'• Point area, and 2) re-exposing hard rock reef at Portuguese Bend and nearshore areas
downcoast of Bunker Point, the beneficial impact, a positive gain in habitat units, is expected to
be significant.
Table 4-9. Net Gain in Habitat Units
With-Project Verses Without-Project
((In AAHUs)
Future Future w/o Change in
Location w/Project Project HUs'
Portuguese Bend (Alt.1) 32.4 10.7 +21.7
Portuguese Bend (Alt. 1a) 59.9 10.7 +49.2
Portuguese Bend (Alt.2) 24.3 10.7 +13.6
Portuguese Bend (Alt. 2a) 50.2 10.7 +39.5
Bunker Pointe 161.9 60.6 +101.3
Bunker Point-Whites Pt2 216.1 89.7 +126.4
'Future With-project minus Future Without-project.
2AAHUs for this area is the same for all action alternatives
1 •
4-29
The total positive net gain are as follows: 011
Alternative 1&3 - 249.4 AAHUs (21.7 + 101.3 + 126.4)
Alternative 1a&3a- 276.9 AAHUs (49.2 + 101.3 + 126.4)
Alternative 2 - 241.3 AAHUs (13.6 + 101.3 + 126.4)
Alternative 2a -267.2 AAHUs (39.5 + 101.3 + 126.4).
Other Environmental Effects
The Draft Environmental Impact Statement/Environmental Impact Report prepared for
the Draft Feasibility Report presents the details on without project conditions and potential
impacts of the alternative plans. Although Alternative 3 is not described in because of the
potential engineering instability of this plan, it is noted that the beneficial and adverse impacts
are expected to be similar to Alternative 1, with the exception that about nine acres outside of
the structure would likely experience recovery, and their would be reduction in benthic marine
environmental behind the structure being adversely impacted. The major areas of concern
related to adverse environmental impacts for each alternative are related to the loss of habitat
within the containment dike areas, which would be offset by the restored areas as described
above. In addition, there is concern with exposing of contaminants that may be buried in the
sediment deposits and the reduction of a source of material that is moving offshore and
capping offshore contaminated sites in Santa Monica Bay. •'
Uncovering Contaminated Sediments
Test results conducted during the Feasibility Study indicate that the sediment quality
within the sediment deposits of Portuguese Bend and surrounding area that is likely to uncover
is within the background levels of Santa Monica Bay and is not considered to cause any
adverse effects.
Contaminated Sediment Offshore
The effects of the reduction of the sediment load from Portuguese Bend on the effluent-
affected contaminated mound offshore is highly speculative. A recent analysis by Drake et al.
(1994) provides the basis for the following discussion and is incorporated by reference as per
40 CFR 1502.21.
By use of predictive models, Drake et al. (1994:45) contend that portions of Portuguese
Bend landslide sediment resides on the inner and middle continental shelf(<60 meters) and is
being moved by currents to deeper waters in the northwest. That sediment is contributing to
covering up the northwestern portion of the effluent-affected contaminated mound. Their
analyses predict that, assuming sedimentation rates from the landslide will decrease the
4-30 •
110 contaminated mound will erode in the northwestern part(Drake et al 1994:49). They further
make predictions of the effect of biological mixing and desorption of DDT.
Discussions with representatives of EPA indicate that the sediment from the Portuguese
Bend Landslide does not contribute a significant source of material to cap the contaminated
areas in Santa Monica Bay. It is also possible that sometime during the life of the project, the
contaminated mound will be remediated, if necessary. This is not an unreasonable assumption,
given the fact that the offshore site of the effluent-affect mound has been identified as a site
for Superfund investigation. As such, the loss of Portuguese Bend sediment which may be.
covering portions of the effluent-affected contaminated mound is probably of no long-term
significance. Further it is noted that under without project conditions the material from the
landslide is distributed over a wide range including areas that are not contaminated. Since the
material from the landslide under with project conditions of all the alternatives will now be
contained behind the dike, the material can be mechanically moved and placed to prove a more
effective cap of contaminated sites.
Water Quality Within the Dike
As the area behind the dike gradually fills with landslide material, the quality of the water
trapped by the dike is expected to significantly deteriorate. The lack of circulation is expected to
significantly alter, at least the dissolved oxygen, pH, turbidity, temperature and possibly several
other parameters. A mathematical analysis was used to estimate the expected interchange of
': volume of water behind the dike that was exchanged during each tidal cycle. The final design
of the structure will includeusing models to assure that the water that enters the enclosed area
behind the dike from the ocean during high tide will drain back out during low tide. About 27%
of the water is exchanged for Alternatives 1 and 2 and 100% of the water is exchanged for
Alternative 3. The exchange will occur every tidal cycle or approximately every 12 hours. This
simple analysis does not account for water exchange due to local waves. During times of
extreme events, significant flushing will occur.
Initial consultations have been conducted with staff from Waterways Experiment
Station's Environmental Lab and Coastal and Hydraulics Lab. It is possible to quantify the
environmental effects to water quality behind the dike provided input parameters such as BOD,
DO, nutrients, etc are measured in the field. The two local streams that drain the landslide
would have to be measured during a storm or series of storms. A hydrodynamic model would
have to be coupled with a water quality model to predict response. A range of numeric models
could be used from very simple to complex depending on the needs.
1, •
4-31
Economic Analysis of Restoration Alternatives 011
The average annual costs per habitat unit for each of the six alternatives are presented
in Table 4-10.
Table 4-10. Total Cost per Average Habitat Unit
for Feasible Alternatives
Average Cost Per
Alternative Annual Cost AAHUs' AAHU
1 $2,384,000 249.4 $9,600
1a $2,697,000 276.9 $9,700
2 $2,137,800 241.3 $8,900
2a $2,439,100 267.2 $9,100
3 $4,590,000 249.4 $18,400
3a $4,909,300 276.9 $17,700
1Net gain in Average Annual Habitat Units
Selection of the NER Plan
Based on Table 4-10, Alternative Plan 2 would create a total of 241.3 AAHUs are
expected at a cost of$8,900/AAHU, while Alternative 2a would create a total of 267.2 AAHUs
at an average annual cost of$9,100. It is recognized that both plans essentially are effective in
restoring and improving the same area, while Alternative 2a would expedite the restoration by
mechanical dredging. Alternative 2 is selected as the NER Plan since it results in restoration of
similar area as Alternative 2a at a more efficient cost.
Evaluation of Alternative Plans
System of Accounts
The positive and negative effects of each alternative are best displayed using the
System of Accounts developed by the U.S. Water Resources Council. The Accounts are
4-32
categories of Environmental, Economic, and other Social Impacts, defined in such a manner
that each alternative can compared to the other, and to expected future without-project
conditions. The Water Resources Council suggests using four accounts to compare proposed
water resource development plans. These accounts are National Economic Development,
Environmental Quality, Regional Development and Other Social Effects.
National Economic Development
The intent of comparing alternatives in terms of National Economic Development(NED) is to
identify the beneficial and adverse effects that they may have on the National economy.
Beneficial effects are considered to be increases in the economic value of the National output
of goods and services attributable to the alternatives. Increases in NED are expressed in terms
of equivalent costs and benefits presented in monetary and non-monetary values and for this
study whose objective is environmental restoration, the analysis reflects the incremental cost for
'II achieving additional non-monetary benefits.
Table 411 presents the NED Account analysis of the alternative plans and compares
the costs of the alternative plans with the non-monetary environmental benefits. It is noted that
there are-several outputs of the project that are likely to occur which have not-been quantified
but are mentioned for consideration in the decision process. This includes increases in
recreation such as scuba diving fishing, and other bottom marine leisure activities, and
commercial harvesting of kelp forests and associated benthic life including lobster, sea urchin,
etc. These benefits are not expected to be significant from an economic standpoint, but does
increase the opportunity for these activities in the Los Angeles Metropolitan area. The
conclusion of the NED analysis indicates that Alternative 2 presents the most cost efficient
means of producing environmental benefits, while Alternative 2a would expedite the restoration
by mechanical dredging.
( �
4-33
Table 4-11. System of Accounts-National Economic Development AccountOil
(October 2000 Price Levels)
No
Category Action Alt. 1 Alt. 1a Alt. 2 Alt. 2a Alt. 3 Alt. 3a
I.Average Annual Habitat Unit Benefit
Total AAHUs 161 410.4 437.9 402.3 408.2 410.4 437.9
Net Increase
AAHUs 0 249.4 276.9 241.3 267.2 249.4 276.9
II.Project Costs
First Costs
Dike $17,140,000 $17,140,000 $23,537,000 $23,537,000 $5,604,000 $5,604,000
Dredging 0 $3,730,000 0 $3,591,000 0 $3,805,000
Total Construct
Costs $17,140,000 $20,870,000 $23,537,000 $27,128,000 $5,604,000 $9,409,000
Real Estate $35,000 $35,000 $35,000 $35,000 $35,000 $35,000
Monitor and $460,000 $460,000 $460,000 $460,000 $460,000 $460,000
Adaptation Plan
PED $1,371,000 $1,669,000 $1,883,000 $2,170,000 $1,150,000 $1,454,000
Constr Mgmt $1,111,000 $1,335,000 $1,525,000 $1,740,000 $363,000 $591,000 III
Total First Costs $20,117,000 $24,369,000 $27,440,000 $31,533,000 $7,612,000 $11,949,000
Interest During
Construction $1,332.800 $1,614,400 $1,817,900 $2,089,100 $504,300 $791,600
Gross Invest int $21449,800 $255983,400 $29,257,900 $33;622.100 $8,116,300 $12,740,600
Annual Costs
Interest and
Amortization(1) $1,481,000 $1,699,300 $1,887,900 $2,199,300 $542,200 $871,600
Dike Repair(2) $85,700 $85,700 $117,700 $117,700 $28,000 $28,000
Dike Rehab(3) $69,400 $69,400 0 0 $2,600.000 $2,600,000
Material Removal
(4) $747,900 $747,900 $0 $0 $1,401,600 $1,401,600
Total Average
Annual Cost $2,384,000 $2,697,000 $2.137,800 $2,439,100 $4,590,000 $4,909,300
Ill.Economic Analysis I
Average Annual I I I I I
Cost per AAHU I I $9,600 I $9,700 I $8,900 I $9,100 I $18,400 I $17,70
(1)Based on 6-5/8%over 50 years
(2) Repairs due to storm waves (0.5%dike construction costs)
(3)Rehabilitation due to possible foundation instability-25%structure rehab at year 25
(4) Material Removal to avoid encroachment of dike:Plan 1 -3,000,000 cy every 20 years;Plan 2-Not required during 50 •
year life 17 million cy to extend another 50 years;Plan 3-730,000 cy every 5 years.
4-34
114
Environmental Quality
The Environmental Quality (EQ)Account is another means of evaluating the
alternatives. The EQ Account is intended to display the long-term effects that the alternatives
may have on significant environmental resources. Significant environmental resources are
defined by the Water Resources Council as those components of the ecological, cultural and
aesthetic environments, which, if affected by an alternative, could have a material bearing on
the decision-making process.
A comparison of the effects that the proposed alternatives may have on EQ resources is
shown in Table 4-12. This table illustrates that the expected beneficial and adverse
environmental impacts from all of the action alternatives are relatively significant with respect to
,� restoration of the kelp bed forests, with much of the benefits related to the impacts of reducing
turbidity to downcoast areas.Alternatives 1 and 1a both restore similar areas of habitat,
however Alternative 1a produces the greatest average annual habitat units primarily as a result
of the earlier restoration provided by mechanically removing the sediment deposits. Alternative
3 results in the greatest area of restoration; however, there is significant uncertainty at this time
regarding the stability of this plan due to impacts of the continuing landslide. -
Other environmental impacts as discussed above are not considered to result in any
significant adverse consequences except behind the containment dike. Further design studies
will be conducted to minimize the adverse impacts that might result from reducedwater quality
behind the containment dike.
4-35
Table 4-12. System of Accounts-Environmental Quality Account —i
sv
cr
Category I No-Action I Alternatives 1 and1A I Alts.2 and 2A I Alts.3 and 3A a
it
I.Physical Environment reit
a.Sluff erosion Continuous erosion of landslide bluff Erosion of landslide bluff prevented.Reduces erosion of Same as Alternative 1 Same as AMemative 1 U
about 170,000 cry a year
yr
b.Sediment Deposition Continued deposition of 01,000 ay a Reduction of erosion and containment of landslide Same as Alternative 1 Same as Alternative 1 LD
year will Increase area and thickness of material will allow for scouring of existing sediment 3
sediment deposits deposits'to a depth of-30 het restoring uncovering about O
40 sores of rooky habitat over time. —+
D
o.Impacts on Landslide Landslide expected to continue.Further No impact on landslide movement expected. Same as Alternative 1 Same as Alternative 1 n
measures by local interests may
reduce or stabilize landslide,however 1 C
effects are uncertain at this time. 7
IA Alt
d.Water Quality Continued erosion of material from bluff Water quality degradation within containment dila will be Same as Alternative 1 Same es ernative 1 l
pt will continue to cause high turbidity minimized with additional design studies.Outside of dike
levels adversely impacting downcoast turbidity will be substantially reduce restoring high quality 7
ecosystem of about 400 acres of kelp forest ecosystem. <
e.Air Quality No Impact.Measures being taken Temporary increase In construction related air quality Same as Alternative 1 Same as Alternative 1 p
expected to continue to improve air Impacts will be minimized through scheduling of 7
quality and reduce number of days of activities to avoid increases In number of non-attainment 3
non-attainment in accordance with days. tD
local plans a
f.Noise Conditions No Impacts. Increase in noise primarily due to Increase in truck traffic Same as Alternative 1 Same as Altematiwt
and construction equipment will be minimized by 0
scheduling activities per local ordinances. Id
g.hazardous and Toxic Material from landslide will continue to Uncovering of contaminated sediment deposits are not Same As Alternative 1 Same as Alternative 1 4Wastes cover offshore contaminant areas. expected to cause any significant adverse impacts.
Reduction of material from landslide as source for D
covering offshore contaminants is not expected to be n
significant impact,material from containment dike could O
be used for future cover. _
7
rr
40
Sit:
r
7 NI
0 • 1111
Table 4-12. System of Accounts -Environmental Quality Account Continued —I
A)
as
II. Biological Environment m
46.
a.Benthic Habitat Continued landslide movement and Loss of disturbed habitat within the 200 feet of coastal Similar to Alternative 1.Loss Similar to Atternativel
erosion of the landslide bluff will marine environment within the containment dike.Outside of marine habitat within the N
Increase area and thickness of dike scouring of sediments will uncover over time of 400 feet of coast between the
sediment covering rocky habitat. about 60 acres of rooky substrate to allow restoration of shoreline and dike.Average C/)
Turbidity adversely Impacts quality of kelp forest ecosystem,reduced turbidity outside of dike annual habitat unit value is N
downcoast kelp forest ecosystem. will improve quality of about 400 acres of rocky habitat 412.3 or Increase of 251.3. e i-
Average annual habitat unit values and kelp forest ecosystem.Average annual habitat unit Plan 2A would accelerate 3
AMU to be 161. value Plan 1.420.4 or increase of 259.4,Plan 1A dredging with total AU of
dredging would accelerate restoration resulting in AMU 416.2 and net Increase of o
total of 447.9 and net increase of 286.9. 277.2 -5'
Vegetation quality degraded due to Lou of vegetation within the dike.Uncovering of rocky Similar to Altemativet Similar to Alternative) n
b.Vegetation sediment deposition and turbidity substrate and reduction in turbidity is expected to restore O
Impacts. high quality kelp forest ecosystem C
7
c.Wildlife General reduction in diversity and Lossof wildlife trapped within dike.Restoration of kelp Similar to Altarnativel Similar to Alternathrol '"F
N
abundance of marine species due to forest ecosystem will increase diversity and abundance
Impacts of continuous sediment of wildlife associated with high quality kelp forest I
deposition and turbidity. ecosystem. Ill
4*.
y d.Terrestrial Habitat Continued landslide movement will No change to landslide movement and impacts on Same as AltematIve 1 Same as Alternative 1 <
continue disturbance of quality of terrestrial habitat.Temporary construction impacts o
terrestrial habitat caused by haul road and general construction activities, 7
Impacts to be minimized by siting haul road to avoid 3
significant adverse Impsots. CD
d.endangered Species Local interest continue working with Haul road to be sited to avoid impacts to endangered and Same es Alternative 1 Same as Alternative 1
ty
Fish and Wildlife Service In preserving threatened species during construction.Dike could
NCCP and associated terrestrial provide roosting area for brown pelican. 0
endangered and threatened species. C
fit
Ill. Cultural Resources
a.Cultural Resources Continued landslide movement, No significant adverse impacts are expected.Further Same as Alternative 1 Same as Alternative 2 0
sediment and turbidity Is not expected testing to be done during preconstruction engineering C)
to adversely Impact on any of the and design. O
marine located cultural resources. C C
b.Aesthetics Open view of ocean will continue as Rock Dike Structure located 200 feet offshore and 2800 Same as Alternative 1 Same as Alternative 1 ()
well as significant turbidity plume. feet long at elevation about 20 feet above MLLW will o
disrupt open ocean view from high spots around 7
Portuguese Bend.Within the dike high turbidity from ''''.
landslide material deposition.Outside breakwater,the 7
turbidy plume will be eliminated to be replaced by kelp N
forest vegetation. O.
Regional Development
11/1
The Regional Development (RD) Account is intended to illustrate the effects that the
proposed alternatives would have on regional economic activity, specifically regional income
and regional employment.
A comparison of the possible effects of the alternatives on these resources is shown in
Table 4-13. In general, all alternatives would be expected to have some beneficial contributions
to the RD Account, based on direct and secondary benefits that would result from increases in
the level of ecological productivity along Portuguese Bend and downcoast areas, and
employment activities during construction. These benefits are not considered to be significant
for any of the alternatives. It is emphasized that none of the alternatives are expected to have
any significant impact on stabilizing the landslide which is the primary factor impacting on
regional development in the area. The alternatives are not designed to create any substantial
buttress or is the amount of sediment deposition behind the containment dike expected to be
adequate to counteract the driving force of the landslide.
Other Social Effects
The Other Social Effects (OSE)Account typically includes long-term community impacts
in the areas of public facilities and services, recreational opportunities, transportation and
traffic, and man-made and natural resources. A comparison of the effects that the proposed
alternatives would have on OSE resources, is also shown on Table 4-13. 4111
In general, the alternatives are expected to have a long-term positive effects for local
residents and visiting publics. The restoration of kelp beds to the region will provide additional
recreation opportunities that existed in the past and was popularly pursued in the area. In
addition recreation boating and fishing in the area is expected to benefit from the plans. None
of the alternatives will result in any benefit that is significantly greater than the others. There
would be some adverse impact to aesthetics and the vista from various high points in the region
as a result of the breakwater structure, and there may be some adverse visual effects related to
the filling in of the containment dike. Accordingly, Alternative 2 would be more preferable to
Alternative 1, because of the less frequent maintenance and rehabilitation of the dike structure
activities would minimize disruptions to the community. Alternative 3 would have the least
impact on aesthetics.
4-38
Table 4-13. System of Accounts - Regional Economic Development
and Other Social Effects Accounts
I. Regional Economic Development
Category No-Action Alternatives 1 & 1A Alternatives 2 &2A Alternatives 3 &3A
a.Employment Degraded condition of Construction activities will Same as Alternative 1. Same as Alternative 1.
ecosystem precludes create some employment
employment opportunities. related to rock quarries
and placement.
b.Business and Industry Degraded condition of Restoration of high quality Same as Alternative 1. Same as Alternative 1.
kelp forest precludes this kelp forest increases
area from commercial opportunities for
harvesting and recreation. commercial harvesting
and snorkeling and scuba
diving.
c.Local Government No investment required Non-Federal Sponsor Investment required is Investment required is for
Finance from Non-Federal investment required for for construction and less construction.Frequent
Sponsor. construction,dike frequent maintenance damage from continuing
rehabilitation,and material costs is expected. landslide could require
removal. repair costs.
d.Growth Inducing Continuous of landslide Will not effect continuing Same as Alternative 1. Same as Alternative 1.
Impacts precludes structural type landslide movement.No
development. change to No-Action.
II. Other Social Effects
10 Category No-Action Alternatives 1 & 1A Alternatives 2&2A Alternatives 3 & 3A
a.Public Health and No major impacts. Public safety impacted by Same as Alternative 1. Same as Alternative 1.
Safety increased traffic Impact
minimized by traffic
control.
b.Recreation Degraded ecosystem and Restoration of high quality Same as Alternative 1. Same as Alternative 1.
continuous turbidity ecosystem and reduced
minimizes opportunities turbidity encourages
for recreation. snorkeling and scuba
diving activities.
c.Traffic No major impacts. Construction traffic and Similar to Alternative 1. Similar to Alternative 1.
Landslide will continue to need for haul road from Less frequent dike More frequent repair and
damage Palos Verdes Palos Verdes Blvd to bluff maintenance and repair maintenance activities.
Boulevard. toe will increase traffic. activities.
Minimized by operations
being off peak and avoid
adverse impacts in siting
haul road.
d.Man-made Resources Landslide continues to No change from No- Same as Alternative 1. Same as Alternative 1.
occur in future unless Action.
further action is taken to
stabilize.
e.Natural Resources Continued degradation of Restoration of over 400 Same as Alternative 1. Same as Alternative 1.
ecosystem. acres of high quality rocky Restoration of 400 acres. Restoration of 400 acres.
habitat and kelp forest
ecosystem.
I •
4-39
Associated Evaluation Criteria
The final array of alternatives were evaluated using four criteria suggested by the U.S.
Water Resources Council, and other criteria mentioned for the decision-making process. These
criteria are outputs, cost effectiveness, significance, acceptability, completeness, effectiveness,
partnership context, and reasonable costs.
Outputs
The environmental outputs of each of the alternative plans will result in the restoration of
kelp forest ecology that is a major functional component of the Southern California Bight area.
The contributions of the rocky habitat and associated kelp forest are recognized by National
Marine Fisheries and State Fish and Game who both have ongoing programs for construction
artificial rocky reefs and have expended considerable funds to restore the kelp forests
surrounding the Palos Verdes Peninsula. The control of erosion and sediment deposition and
turbidity along the Portuguese Bend area will further contribute to these endeavors. Alternative
3 would result in the greatest contribution to potential output although the stability of this plan is
uncertain at this time. Alternatives 1 and 1a would be the next best plan of providing greatest
output, with Alternative 1a resulting in expediting the uncovering of rocky habitat through
mechanical dredging.
Cost Effectiveness ,
Alternative 2 provides the greatest cost effectiveness of the alternative plans considered
when comparing average annual habitat units with average annual cost. See Efficiency below
for additional information on the cost effectiveness of the alternatives.
Significance
The restoration of rocky habitat and associated kelp forest is considered of extreme
value in the Southern California area that is primarily dominated by mud and unconsolidated
soft bottom habitat areas. The restoration of the Portuguese Bend area rocky habitat, which
was part of the expansive Palos Verde kelp forest system, is considered extremely significant
as part of the kelp forest ecosystem that provides among the highest diverse and abundant
habitat conditions in nature. The giant kelp forest is inhabited by a species-rich invertebrate
fauna. Literally hundreds of species have been recorded in this habitat type. The diversity of
morphologies, feeding types, and behaviors is outstanding. As a brief summary, the kelp forest
is typically rich in filter/suspension/detritus feeders like sponges, anemones, corals, sea
cucumbers, clams, and mussels. Grazers like sea urchins, abalone isopods, amphipods, and
sea snails are all common. Among the predators, sea stars, crabs, spiny lobster, octopus, and
squids are all regular inhabitants of the kelp forest. The value of these habitats are also
considered significant from agency perspectives and previously discussed with the ongoing
programs by National Marine Fisheries and California State Fish and Game. With respect to the
alternative plans, each of the plans would contribute significant restoration opportunities.
ill
4-40
Acceptability
The concept of restoration of the Portuguese Bend ecosystem is one that in general is
supported by all interests and agencies. However, there are concerns on the effectiveness of
the alternatives, the impact of the landslide, and the overall cost of the alternative which
provides some doubts and concerns of many interests. There has also been concerns raised by
some interests with respect to potential of uncovering contaminated sediments, and reducing
sediment source to capping offshore contaminated areas. These latter concerns have been
addressed to the extent practicable and do not appear to be a significant adverse problem.
However, further coordination of the Feasibility Study results including the expected costs and
benefits, and other impact concerns such as aesthetics and loss of the containment basin will
further define community and agency acceptability of the Recommended Plan.
Completeness
Completeness is a determination of whether or not an alternative includes all elements
necessary to achieve its objectives. In general, the alternatives are all complete. Alternatives 1,
1a, 2 and 2a are considered complete. No further measures are needed to allow for the
functioning of the alternatives. However, there is a high degree of uncertainty with respect to
Alternative Plan 3 which is located on an area that appears still to be actively moving. Based on
measurements to date, part of the area may be stable, while other parts are moving. Because
of the relatively short period of time that the GPS stations have been set along the shore, there
is substantial uncertainty at this time on the long-term location and amount of movement that
may be expected along the coast. In addition, there is a high degree of uncertainty on how a
structure built on the moving foundation will function, get damaged, and type of repairs needed
as well as frequency and cost of repairs. Accordingly, Alternative 3 is not considered a
complete or sound plan at this time. However, if future long-term monitoring indicates the area
has stabilized, there may be less of a risk in building Alternative 3.
Effectiveness
Effectiveness is defined as a measure of the extent to which an alternative achieves its
objective. In this regard, all the plans are expected to be effective in restoring the rocky habitat
and reestablishment of the kelp forest. There is support of this effectiveness in the experience
when the City constructed gabion structures along the landslide bluff. Soon after the gabions
were built and sediment turbidity as well as some scouring occurred, kelp strands began to
appear in the Portuguese Bend Cove area. However, once the gabions were destroyed from
wave attack and slide movement, the kelp area degraded.
Efficiency
Similar to cost effectiveness, efficiency analyzes whether there any other more cost
effective means in providing the same output. In this regard, a comparison is made between the
. cost of the alternatives with the cost of constructing similar rocky habitat such as a low profile
artificial reef.
4-41
In 1996, the California Department of Fish and Game (CDF&G) provided the California
Coastal Commission (CCC) a cost estimate of building a low profile artificial reef. The request 411011-
was made by the CCC in an attempt to get a"handle" on what the cost to an applicant might be
should the CCC require an applicant to construct a low profile artificial reef as mitigation for
impacts to existing natural rocky reef. Dennis Bedford (Coordinator of CDF&G's Artificial Reef
Program) provided an estimate of$18,847,755 to construct 100 acres of artificial reef with
coverage of 67% of the ocean bottom. This translates to a cost of about$13,000/acre of reef
habitat.
Although not directly comparable to this analysis, the cost estimate shows what
regulatory agencies might consider as being a "reasonable" cost for mitigating impacts to rock
reef habitat in the Southern California marine environment. (For comparison with the analysis
of this appendix— if you conservatively assume the 100 acres of artificial reef created would
provide prime habitat at or near the value of 1.0 HUs over the life of the restoration effort, you
could call the cost$13,000/AAHU.)
The cost of Alternative 2 $2,137,800, involves restoring some 97 acres of hard rock reef
and eliminating turbidity impacts on 368 acres of existing reef-for a total of some 565 acres
restored. The cost per acre could be considered $3,800/acre, or$8,900/AAHU. Accordingly, the
cost of the alternatives assuming similar restoration productivity is less than the cost of
constructing low profile artificial reefs.
Partnership Context
(110
The Non-Federal Sponsor for the cost-shared Feasibility Study has continued to express
interest and support for the study and the environmental restoration of the Portuguese Bend
and adjacent areas. Coordination with the Department of National Marine Fisheries and
California State Fish and Game also indicated support for the Feasibility Study and alternatives
subject to completion of the Final Feasibility Report. As noted, both of these agencies have
been actively involved in restoration efforts along Palos Verdes Peninsula and continuously
monitor conditions. The U.S. Fish and Wildlife Service has expressed strong concerns with the
proceeding with the project indicating major questions on uncovering of contaminated sediment
and impacts on reducing sediment to capping of downcast offshore areas. They also have
indicated concerns on the effectiveness of the plan, and to some degree the value of the
habitat. These concerns have been addressed and are presented in the Draft Feasibility Report
and Draft EIS/EIR. It is expected that further clarification of the views of the Non-Federal
Sponsor, agencies, and other interests will result during the public review period.
Reasonableness of Cost
Again, referring to the cost of constructing artificial reefs as a similar habit, the costs of
the alternatives appear reasonable, with Altemativel providing the most output per dollar spent.
In comparison to the cost of constructing other types of rocky habitat, it is noted that the cost for
reconstructing wetlands by the Port of Long Beach, and the cost of wetland restoration at Bolsa
Chica and Batiquitos Lagoon range from $50,000 to $150,000 an acre. It is noted that these
habitat types are not similar, and the value of these habitats are arguably different, but this II,
does give one a relative understanding of the cost and acres of habitat created.
4-42
AnalMO ysis
A ysis
Action Versus No-Action
The first tradeoff to be considered in evaluating the final alternatives is to distinguish
between the No-Action Alternative and the other alternatives. The major tradeoff between them
is that the problems and needs defined under the without-project condition will continue if no
action is taken. Of course, the costs and other resources for implementing any of the
alternatives will also not be incurred and therefore may be available for other needs. In general,
the trade-off between action and No-Action is to allow the degraded condition of Portuguese
Bend and adjacent areas to continue in the future.
Tradeoffs between Action Alternatives
The second level of tradeoffs are those between the action alternatives. From an NED
standpoint, Alternative 1 provides the greatest environmental output per dollar spent.
From an EQ standpoint, the tradeoff between alternatives are not that significant,
although the earlier removal of sediment and uncovering of rocky substrate will result in greater
value of average annual habitat units for Alternative 1a.
00 From RD and OSE standpoints, the major tradeoff is the restoration of the environment
which will provide additional recreation and commercial fishing opportunities, as well as scuba
diving.An unavoidable impact is the change in aesthetics caused by the rocky dike and
containment area which could be unacceptable to many interests.
Selection of the Recommended Plan
Alternative 2, the NER Plan, is selected as the Recommended Plan. Although
Alternative 2A would result in earlier uncovering of sediment to expose the rocky substrate, the
additional costs for mechanically removing the material does not increase average annual
habitat units sufficiently to justify the additional cost. Altematives1 and 1a have the potential for
the need for rehabilitation of the dike structure because of unstable foundation and more
frequent removal of material from the sediment basin that might impact on the dike structure.
The additional cost of constructing the dike further offshore in deeper water is less than the
rehabilitation costs and the cost of the two maintenance operations are expected to be
required for Alternative 1 during the 50-year project life. It is noted that the representatives of
the City of Rancho Palos Verdes have indicated interest in locating the dike structure nearer to
shore, and are continuing to monitor the nearshore area to determine if the foundation closer
to shore is stable, which could possibly reduce project costs. However, at this time, stabilization
of the landslide is not expected in the near future.
•
4-43
Risk and Uncertainty
There are numerous uncertainties related to defining the problem and solutions which
have been addressed throughout the Feasibility Study and formulating the Recommended
Plan. The nature, location, and future of the landslide have been investigated by the Corps of
Engineers and numerous other interests. The identification of the slide plane and toe of the
slide could not be definitely established; however,the location of stable foundations were
discovered, and geologic information was interpreted conservatively to define alternative
locations for structural improvements.Accordingly, the engineering soundness of the dike
foundation is considered reasonably certain.
The continuation of the landslide and its impact on the containment dike was also
conservatively estimated using long term average historic rates of movement. Recent trends
appear to indicate a slower rate of movement may be occurring, which may reduce the need for
maintenance removal of material in the containment area.
The rate of uncovering sediment deposits was also based on long term analysis of wave
conditions expected sediment movement. It is possible that one or two major long duration
storms similar to that occurring in the 1980s occurring early after construction of the
dikes is completed could result in faster uncover rates. However, the majority of the benefits
associated with reducing turbidity is expected to occur immediately after construction.
Based on experiences with the gabion structures and the historic presence and recovery
of kelp forests along the Palos Verdes Peninsula, experts studying kelp forests in the area all
agree that they expect the Recommended Plan to be effective, and that recovery of the
ecosystem is expected with the implementation of the Recommended Plan.
Sensitivity Analysis
•
Coordination was conducted with representatives of U.S. Fish and Wildlife Service,
National Marine Fisheries Service, and the Midcontinent Ecological Science Center on the
methodologies used to develop habitat values. It was generally agreed that the model used for
examining habitat changes as described in the EIS/EIR was an appropriate tool for use on the
Rancho Palos Verdes Study and that the model's output was an appropriate measure of habitat
suitability. However, there was still uncertainty regarding the value of the habitat produced by
the model. In this regard, it was agreed to do sensitivity analysis varying performance of the
recommended plan with respect to the level of restoration that would result from the proposed
plan as compared to the reference area, as well as possible variances in recovery rates to
reach restored conditions. These sensitivity analysis were completed and showed resulting
increases in average annual habitat values ranging from (1)172 AAHU if recovery achieved was
only 80% of the reference area; and (2) 163 AAHU if recovery achieved was only 80% of the
referenced area and also the rate of recovery took five years instead of one year. Details of the
analysis are presented in the draft EIS/EIR. For the proposed recommended plan, this would
reflect increases in the average annual cost per average annual habitat unit of$12,500 to
$13,100. Based on comparing these costs to the costs of artificial reef construction, the
recommended plan is still considered to be of reasonable cost for restoring marine rocky habitat
and kelp forest ecosystem.
4-44
40
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