HomeMy WebLinkAboutCC AG PKT 2009-01-26 #LAGENDA STAFF REPORT
DATE: January 26, 2009
TO: Honorable Mayor and City Council
THRU: David Carmany, City Manager
FROM: Vince Mastrosimone, Director of Public Works
SUBJECT: BEACH MAINTENANCE FEDERAL COST SHARING
REPORT
SUMMARY OF REGIUEST:
It is respectfully requested that the City Council receive and file the Beach
Maintenance Federal Cost Sharing Report prepared by Moffatt & Nichol,
December 2008.
BACKGROUND:
Staff is pursuing an agreement with the United States Army Corps of Engineers
(USAGE) to have the Federal government assume responsibility for the periodic
beach nourishment required on East Beach. The report prepared by Moffatt &
Nichol provides a history of why beach nourishment is required, how it was
accomplished in the past and makes the case for the USAGE to assume financial
and operational responsibility for future beach nourishment projects.
The report will be used as a reference for our efforts to have USAGE take on this
responsibility. It will be used by our lobbying team to provide information for
discussions with elected officials. Also, it will be used to justify our request of
USAGE staff for support of our efforts.
FINANCIAL IMPACT:
There is no financial impact associated with receiving and filing this report.
RECOMMENDATION:
It is respectfully recommended that the City Council receive and file the Beach
Maintenance Federal Cost Sharing Report prepared by Moffatt & Nichol,
December 2008.
SU BY:
Vince Mastrosimone
Director of Public Works
NOTED AND APPROVED:
~ro~~'"')
David Carma y, City Manager
Attachments: A. Justification for Reassessment of Beach Maintenance Federal Cost
Sharing Agreement, December 2008
Agenda Item L
Justification for Reassessment of Beach Maintenance
Federal Cost-Sharing Agreement
Between
the City of Seal Beach
and
U.S. Army Corps of Engineers
City Manager's Office
Cit~of Seal Beach
211 8 Street, 2nd Floor
Seal Beach, CA 90740
December 2008
®®
WOFFATT & NICHOL
MB<N File: 3874-20
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EXECUTIVE SUMMARY
Additional Federal actions are needed at Seal Beach to protect the eastern portion of
the City beach (East Beach) from active erosion caused by Federal navigation works.
Seal Beach Naval Weapons Station (SBNWS) was installed at Anaheim Bay in the
1ta40's. The navigation entrance channel to the SBNWS includes two long jetties in an
"arrowhead" configuration, extending seaward and pointing toward each other at oblique
angles to the shore. Prior to the construction of the jetties, Seal Beach did not
experience erosion. These jetties cause significant, ongoing erosion on both sides of
the entrance channel at East Beach and Surfside Colony at Seal Beach. The erosion
results in loss of sand, narrowing of the beach, and periodic but severe coastal storm
flooding.
The U.S. Army Corps of Engineers (USAGE) agreed to implement the Surfside/ Sunset
Beach Nourishment Project (Surfside/Sunset Beach project) in response to these
erosion problems. This project regularly nourishes the beach at Surfside/Sunset Beach
with coarse sand to address erosion east of the navigation entrance channel, and that
project component is successful. The project also included construction of a concrete
groin at Seal Beach pier west of the navigation entrance channel to address erosion at
East Beach, but that project was only marginally successful. East Beach still
experiences erosion caused by the effects of the jetties and the groin is not fully
effective in mitigating these problems.
Both the USAGE and the City assumed the groin constructed at East Beach would
alleviate the need for major sand replenishment, but minor maintenance with small
nourishment events may be needed. The original agreement between the USAGE and
City stipulated that future small-scale nourishment would be a "maintenance"
responsibility of the City. The decision to build the groin and require the City to maintain
the beach was sound at that time based on available information, and the City has
maintained the beach (and the groin) to reduce the erosion wndition. Monitoring of
maintenance actions has identified that adding moderate amounts of relatively coarse
sand on a regular basis (every five to ten years) to East Beach results in sufficient sand
remaining on the beach to adequately protect against coastal flooding. Sources of
coarse sand for maintenance by the City are not readily available and are therefore not
economical for maintenance. The City has access to poon:r-quality sand, but tfiis does
not provide adequate shore protection. Therefore, Seal Beach cannot sustain its
maintenance requirement of the beach.
Adding a nourishment project using coarse sand at East Beach to the existing
Federally-appropriated Surfside/Sunset project would mitigate the erosion problem
caused by the Anaheim Bay jetties with only incrementally-increased public costs. For
context, the USAGE adds approximately 2 million cubic yards of coarse sand to
Surfside Colony/Sunset Beach every five to ten years, while East Beach would require
approximately 100,000 cubic yams of coarse sand (1/20"' or 5% of that required at
Justification for Reassessment of
Beach Maintenance Federal CostSharing Agreement
.~
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E.:~01~ ~`~ ~'
~IOFFATT & ~ICIfOL
Surfside) from the same source at the same interval to be fully protected and allow the
City to sustain its maintenance requirement.
The USACE still bears the responsibility of renourishing East Beach with coarse sand
as it currently does at SurfsidelSunset Beach due to the following facts:
1. A Federal (USACE) project created the City's erosion problem;
2. City engineers had no role in the design of the mitigation project (pier groin with
on-going City maintenance); and
3. The City cannot sustain its maintenance requirement due to the excessively high
cost of coarse sand required for successful protection.
The Federal government should pay for minor added work at East Beach in spite of the
previous contractural agreement about the groin and City maintenance requirement.
Justification for Reassessment of
Beach Maintenance Federal Cost-Sharing Agreement
~?A~'_~•i\ I
NOFFA71' & NICHOL
CONTENTS
1. INTRODUCTION ........................................................................................................1
1.1 BACKGROUND .............................................................................................2
1.2 PHYSICAL SETTING ....................................................................................2
2. STATEMENT OF THE PROBLEM .............................................................................3
3. COASTAL PROCESSES ANALYSIS ........................................................................7
3.1 WAVES AND SEDIMENT SUPPLY ...............................................................7
3.2. WAVE REFLECTION, AMPLIFICATION, AND LONGSHORE
SEDIMENT TRANSPORT ............................................................................7
3.3 SEDIMENT CHARACTERISTICS
10
3.4 BEACH PROFILE .........................................................................................15
4. BEACH NOURISHMENT .........................................................................................15
4.1 FLOODING EPISODES
4.2 NOURISHMENT HISTORY
15
17
4.3 ANALYSES OF BEACH NOURISHMENT SCENARIOS ...........................19
5. ANALYSIS OF 1985 BEACH EROSION CONTROL STUDY ..................................27
6. CONCLUSION .........................................................................................................28
7. REFERENCES .........................................................................................................30
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MOFFaTT & NICHOL
LIST OF FIGURES
FIGURE 1A Location of Seal Beach Within the San Pedro Littoral Cell
FIGURE 18 Vicinity Map
FIGURE 2 Wave Exposure at Seal Beach
FIGURE 3A Wave Reflection Toward East Beach, Photograph 1
FIGURE 3B Wave Amplification at 13~' and Dolphin Streets, Photograph 2
FIGURE 4 Sediment Budget for Seal Beach
FIGURE 5 East Beach Wave Amplification and Longshore Transport Direction
FIGURE 6 Wave Overwash at East Beach in 1983
FIGURE 7 Flooding from Wave Overwash at East Beach in 1997
FIGURE 8 East Beach Winter Dike in 2006
FIGURE 9 Existing Sand Gradation at East Beach
FIGURE 10 Beach Profiles Surveyed on February 3, 1999
FIGURE 11 Sand Excavation from the Santa Ana River in 1995 by the
USACE Contractor
FIGURE 12 Sand Delivered by Truck from the Sarrta Ana River and
Spread at East Beach
FIGURE 13 Sand Loaded Onto Trains at Palmdale to be Delivered to East Beach
FIGURE 14 Sand Delivered by Rail Being Spread and Sampled at East Beach
FIGURE 15 Previous Gradation Analysis of Sand From Anaheim Bay and From
Palmdale
FIGURE 16 Equilibrium Beach Profile for Anaheim Bay Sand
FIGURE 17 Equilibrium Beach Profile for Coarser Sand (Desert Sand in this
Example)
FIGURE 18 Gradation Curve of East Beach and Offshore Borrow Site
FIGURE 19 Offshore Borrow Site Borings
LIST OF TABLES
TABLE 1 Nourishment History at East Beach
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1. Introduction
The purpose of this report is to assess whether it is justifiable to request
consideration by the U.S. Arrny Corps of Engineers (USAGE) to inGude the East
Beach nourishment project in the Surfside/Sunset Beach Nourishment Project
(Surfside/Sunset Beach project). This report provides information useful to
determine if additional nourishment at the City's East Beach should be included in
future Federal beach nourishment projects at Surfside/Sunset Beach.
The report concludes that justification exists for the Federal government to add a small
nourishment project with coarse sand at East Beach in Seal Beach to the
Surfside/Sunset Beach project. Seal Beach Naval Weapons Station (SBNWS) was
installed at Anaheim Bay in the 1940's. The navigation entrance channel to the
SBNWS includes two long jetties in an "arrowhead" configuration, extending seaward
and pointing toward each other at oblique angles to the shore. Prior to the construction
of the jetties, Seal Beach did not experience erosion. These jetties cause significant,
ongoing erosion on both sides of the entrance channel at East Beach and Surfside
Colony at Seal Beach. The erosion results in loss of sand, narrowing of the beach, and
periodic but severe coastal storm flooding.
The USAGE regularly nourishes the beach at Surfside/Sunset Beach with coarse
sand to address erosion east of the navigation entrance channel, and that project is
successful. The USAGE constructed a concrete groin at Seal Beach pier west of the
navigation entrance channel to address erosion at East Beach and required the City
to perform ongoing maintenance of the groin and the beach, but that project was
only marginally successful. East Beach still experiences erosion caused by the
effects of the jetties and the groin is not fully effective in mitigating these problems.
Both the USAGE and the City assumed the groin constructed at East Beach would
alleviate the need for major sand replenishment, but minor maintenance with small
nourishment events may be needed. The original agreement between the USAGE
and City stipulated that future small-scale nourishment would be a "maintenance"
responsibility of the City. The decision to build the groin and require the City to
maintain the beach was sound at that time based on available information, and the
City has maintained the beach (and the groin) to reduce the erosion condition.
Monitoring of maintenance actions has identified that adding moderate amounts of
relatively coarse sand on a regular basis (every five to ten years) to East Beach
results in sufficient sand remaining on the beach to adequately protect against
coastal flooding. Sources of coarse sand for maintenance by the City an: not readily
available and are therefore not economical for maintenance. The City has access to
poorer~uality sand, but this does not provide adequate shore protection.
Justification for Reassessment of
Beach Maintenance Federal CostSharing l~reement
~~~~~:
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AIOFFATT & NtC1i0L
1.1 Background
Seal Beach is located in northern Orange County, California, between the City of
Long Beach and the Seal Beach Naval Weapons Station. The east end of Seal
Beach, called East Beach, is erosive and experiences flooding during conditions
of combined high tides and high waves. The erosion is associated with effects
caused by the west Anaheim Bay Jetty (City of Seal Beach 1991). The USACE
constructed the jetty for federal navigation purposes. Avery similar problem
exists on the downcoast side of the east harbor entrance channel jetty. The
USACE mitigates beach erosion caused by installation of the harbor by
nourishing Surtside/Sunset Beach approximately every five to ten years as part
of the Surtside/Sunset Beach Nourishment Project.
East Beach does not receive sand as part of the Surtside/Sunset Beach
Nourishment Project because the USACE installed a groin under Seal Beach
Pier in 1959 to mitigate erosion at Seal Beach. The City agreed to this as a
permanent fix to the problem at that time, without fully knowing the ultimate
effects of the Anaheim Bay jetties and the limited ability of the groin to address
these effects. Since harbor construction, Seal Beach experiences various
effects from the west Anaheim Bay jetty at East Beach that warrant more
detailed consideration by the government of whether East Beach should receive
sand as part of the Surtside/Sunset Beach project.
1.2 Physical Setting
The Seal Beach Littoral Cell is part of the larger San Pedro Littoral Cell, as
shown in Figure 1A, and forms a pocket beach bounded to the south by the
Anaheim Bay west jetty and to the north by the San Gabriel River east jetty, as
shown in Figure 1 B. Approximately one mile of coastline lies along the
southwest City boundary.
The City's beach serves as a major local and regional attraction and is a
favorite recreational location for both residents and visitors. Approximately
2,000,000 visitors came to visit Seal Beach last year. Substantial economic
benefits to local businesses and the City are derived from the presence of the
beach. Public access is available through City-owned parking lots on both sides of
the Seal Beach Pier and residential streets that connect Ocean Avenue to the
beach.
The USACE installed a 750-foot long concrete sheet pile groin located
immediately adjacent to the west side of Seal Beach Pier. The groin extends
seaward to an approximate depth of -12 feet mean lower low water (MLLW). This
structure effectively divides Seal Beach into two beach cells -one at East Beach
and one at West Beach. West Beach is approximately 2,600 feet long and varies in
Justification for Reassessment of
Beach Maintenance Federal CostSharing P~greement
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\tOFFATT & MCHOL
width from approximately 1,200 feet at the west end to 250 feet at the east end
adjacent to the groin. East Beach is 2,400 feet long and varies in width (depending
on seasonal and yearly conditions) from 500 feet at the west end adjacent to the
groin to 100 feet at Dolphin Street and to 500 feet at the east end adjacent to the
west jetty of Anaheim Bay.
2. Statement of the Problem
Federally-constructed jetties at Anaheim Bay and the San Gabriel River mouth altered
the littoral processes that affect sediment transport at Seal Beach. Construction of
jetties on both sides of Seal Beach has transformed the shoreline into a pocket beach
which is almost totally isolated from sand transport from adjacent beaches. Upstream
flood control improvements to the San Gabriel River and its tributaries have caused a
dramatic decrease in the amount of sand supplied by the river to the beach. Although
the Seal Beach groin was constructed in 1959 to mitigate the sand loss effects of the
Anaheim Bay Jetties, it is not of sufficient length to stop the westward movement of
sand from East Beach to West Beach. Consequently, East Beach continues to lose
sand annually while West Beach accretes.
The west Anaheim Bay Jetty causes waves to reflect and combine with subsequent
incident waves and create higher run-up on East Beach than under pre-jetty conditions.
In addition, exaggerated longshore currents erode East Beach resulting in insufficient
sand volume to buffer the shoreline from these amplified wave conditions and elevated
wave run-up. The existing beach elevation is too low to prevent high wave runup and
overtopping during winter storms, and consequently waves periodically overtop East
Beach and flood adjacent residences. East Beach is particularly vulnerable to waves
overtopping the beach berm and flooding oceanfront residents when winter storms
occur during periods of high tide. Beach sand management in the form of sand
backpassing and sand dike construction is required to offset the effects of beach
erosion and coastal flooding that occurs under these combined high tide and high
wave winter conditions. The risk of being inundated by storm waves is even higher
during EI Niflo periods.
Beach erosion at East Beach has diminished its capacity for recreation and
protection of adjacent structures. As a result, less economic benefit is generated
from local citizens and visitors, and economic losses occur during severe storm wave
events from damage or business shutdowns. The City continues to seek to replenish
its eroded beach to resurrect declining beach use, provide improved protection to
public infrastructure, the pier, the promenade, and parking lots and to help maintain
the local economy. The City attempts to protect infrastructure and private property from
severe storm waves by actively managing the sand that is available to them. To do this
the City does the following:
Justfiption for Reassessment of
Beach Mairrtenance Federal Cost-Sharing AgraemeM
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NOFF:1Tr & MCHOL
• constructs a protective sand dike each winter (known as the 'winter dike');
• backpasses sand from West Beach to East Beach bi-annually; and
nourishes East Beach when opportunities arise.
A review of the most recent nourishment projects at East Beach indicates that beach
nourishment is most effective when coarse-grained sand is used at East Beach.
However, nearby sources of this sand type are limited and transport costs are an
excessive financial burden to the City. To effectively implement along-term solution, the
City must plan periodic beach nourishment projects at East Beach with coarse sand.
The Surfside/Sunset Beach Nourishment Project conducted by the USACE presents the
best opportunity for the City to nourish its beaches with the necessary coarse-grained
material and share the costs with a Federal partner. It is for this reason that the City of
Seal Beach seeks to have the Beach Maintenance Federal Cost-Sharing Agreement
reassessed.
Adding a nourishment project using warse sand at East Beach to the existing
Federally-appropriated Surfside/Sunset project would mitigate the erosion problem
caused by the Anaheim Bay jetties with only incrementally-increased public costs. For
context, the USACE adds approximately 2 million cubic yards of coarse sand to
Surfside Colony/Sunset Beach every five to ten years, while East Beach would require
approximately 100,000 cubic yards of coarse sand (1/20"' or 5% of that required at
Surfside) from the same source at the same interval to be fully protected.
To the extent that a Federal (USACE) project created the City's erosion problem, and
that City engineers had no role in the design of the mitigation project (pier groin with on-
going City maintenance), the USACE still bears the responsibility of renourishing Seal
Beach with coarse sand as it currently does at Surfside/Sunset Beach. The Federal
government should pay for minor added work at East Beach in spite of the previous
contractural agreement about the groin and City maintenance requirement.
Justification for Reassessment of 4
Beach Maintenance Federal Cost-Sharing /~reement
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Figure 1A -Location of Seal Beach Within the San Pedro Littoral Cell
Justification for Reassessment of
Beach Mairrtenance Federal Cost-Sharing agreement
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Justification for Reassessment of B
Beach Maintenance Federal Cost-Sharing Agreement
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S10FF.4TT & YICHOL
3. Coastal Processes Analysis
Seal Beach is unique in that it behaves similarly to pocket beaches which are found
all up and down the California coastline. Such beaches typically reside between
two rocky headlands which retain the sand on the beach. In the case of Seal Beach,
man-made jetties at the San Gabriel River and at Anaheim Bay act the same as
rocky headlands, trapping sediment that originates from the San Gabriel River from
moving further downcoast. The volume of sand moving into or out of a pocket beach
is typically low and because of this they tend to be stable beaches. Nearby rivers
and streams supply the sediment and waves and currents deliver the beach-grain
sand to the shoreline. However, upstream flood control improvements to the San
Gabriel River and its tributaries have caused a dramatic decrease in the amount of
sand supplied by the river to the beach.
3.1 Waves and Sediment Suooly
Sand in the Seal Beach pocket is transported from east to west by the artificial
effect of a reversed longshore current caused by wave reflection aff the west
Anaheim Bay jetty. Sand is continually lost from East Beach to West Beach so that
East Beach continues to narrow while West Beach wntinues to accrete.
Consequently, the profile of the beach at East Beach is relatively steep and the
beach is narrow, while the profile at West Beach is relative flat and the beach is
wide.
Waves approach East Beach from a directional window oriented to the south
through the northwest as shown in Figure 2. Northwest swell and southerly seas
typically approach the site in winter while southern hemisphere swell and tropical
hurricane swell approach in summer. High waves are usually due to the combination of
northern swell and locally-generated seas during the winter. Most coastal flooding
and storm damage is due to these high waves which have breaking wave heights
as high as 18 feet for an event with a 10-year recurrence interval. The locally
generated seas have wave periods ranging from 6 to 14 seconds and the swells
have periods ranging from 12 to 22 seconds.
3 2 Wave Reflection Amplification and Lonashore Sediment Transport
The Long Beach offshore breakwater shelters Seal Beach from waves approaching
from the west. This significantly reduces the amount of easterly sand transport which
would tend to nourish the eastem segments of East Beach and West Beach.
Additionally, wave energy reflection caused by the Anaheim Bay western jetty has
resulted in a local increase in westerly sand transport at the eastem end of East
Beach. Waves approaching from the west are reflected off the jetty and redirected
toward Seal Beach as shown in Figures 3A and 3B. This mechanism is illustrated by
the waffle wave pattern in Photograph 1, which is caused by the intersection of
Justfication for Reassessment of ~
Beach Maintenance Federal CostSharing Agreement
~ ~~
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ntOFFaTT & NiCHOL
CRUZ IS , ///j/%
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Figure 2 -Wave Exposure at Seal Beach
Justification for Reassessment of 8
Beach Maintenance Federal Cost-Sharing Agreement
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rtot~:tTr & mcxoL
Figure 3B -Wave Ampi'fication at 13"' and Dolphin Streets, Photograph 2
Justfication for Reassessment of
Beach Maintenance Federal Cost-Sharing Agreement
Figure 3A -Wave Reflection Toward East Beach, Photograph 1
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SIOFF:-Tr & MCHOL
reflected and incident waves. Photograph 3B shows the amplification of wave energy in
the vicinity of 13~h Street and Dolphin Street due to intersecting wave trains. As a result,
longshore sediment transport is significantly increased at this specific location, causing
erosion. The narrowest dry beach width occurs between 13~' and Dolphin Streets,
where the farthest landward position of the Mean Lower Low Water (MLLW) contour
lies. As seen in Figure 1 B, the dry beach areas adjacent to the San Gabriel River
and the Anaheim Bay west jetty are wider than at 13"' Street.
According to a previous sediment budget analysis, East Beach is losing material
which moves around and over the Pier groin, offshore and through the west jetty of
Anaheim Bay, at a rate of 4,200 to 7,800 cubic yards (CY) per year (Moffatt 8 Nichol
Engineers 1984). The USAGE presents a sediment budget showing a slightly
greater loss of 8,000 CY of sand per year shown in Figure 4 (USAGE 2002). This
causes the beach to recede at roughly 1.75 to 3.25 feet per year. As a result, East
Beach becomes relatively narrow and low, and can be overtopped by storm waves
at higher tides. The City of Seal Beach has facilitated protection of residences directly
behind East Beach from winter storms by constructing a sand dike on the beach
between the residences and the ocean. Figure 6 shows evidence of a wave
overwash event in 1983 with the winter dike installed, and Figure 7 shows wave
overwash in 1997. The dike is generally effective, but occasionally becomes
overtopped by storm waves. Figure 8 shows the typical winter dike configuration.
3.3 Sediment Characteristics
Sand grain sizes vary dramatically from East Beach to West Beach, being distinctly
coarser at East Beach. High wave energy from wave amplification readily removes
finer-grained sand from East Beach and transports it to West Beach, leaving the coarser
sand behind and creating a Gear distinction of sand conditions from one side of the
groin to the other. Wave amplifigtion and longshore transport of sediment are depicted
in the aerial image in Figure 5.
Generally, the low and deep portion of the beach profile (below the -6 foot MLLW
contour and deeper) along both East and West Beaches consists of poorly graded,
fine (0.06 to 0.11 millimeters, or mm) silty sand forming a relative flat slope. The
higher and steeper portions of the beach profile above mean sea level consist of
poorly graded, coarser sands (0.12 to 0.6 mm). The sand on the higher part of East
Beach is coarser than the sand on the higher part of West Beach. East Beach sand
averages grain sizes of approximately 0.45 mm due to the higher incident wave
energy there. Figure 9 shows an envelope of existing sand grain sizes at East Beach
with sand from Anaheim Bay. Data for the Anaheim Bay sand is based on all samples
considered together.
Justficetion for Reassessment of t0
Beach Maintenance Federal Cost-Sharing Agreement
®®
AfOFFATT & NICHOL
LOSS "
Through
San Gabriel
River Jetty
Budget of Sediment
Seal Beach Littoral Cell
1963-1994
Aeolian Loss NoudshmeM Backpassing Aeolian Loss Overwash Loss Nourishment
Weal Beack
22
ContdbuUon
from
San Gabriel
River
Profile
Aocumulalfon
33
18
Saar Beaek
ProUle
Accumuldlon
F~
Offshore Loss Offshore Loss
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ii 0 n 1
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Loss l0
Anaheim
Bay
Note: All quantities represent thousands of cubic yaMS per year.
Source: USACE, Caast of Cal'domia Storm and Tidal Wave Study, South Coast Region, Orange County, December 2002.
Figure 4 -Sediment Budget for Seal Beach
Justification for Reassessment of ~ ~
Beach Maintenance Federal Cost-Sharing Agreement
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Figure 5 -East Beach Wave Amplification and Longshore Transport
Direction
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Justification for Reassessment of 12
Beach Maintenance Federel Cost-Sharing Agreement
Figure 6 -Wave Overwash at East Beach in 1983
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Figure 8 -East Beach Winter Dike in 2006
Justfication for Reassessment of 13
Beach Maintenance Federel Cost-Sharing Agreement
Figure 7 -Flooding from Wave Overwash at East Beach in 1997
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AIORRATT & NICHOL
100%
90%
BO%
70%
60%
3
a 50%
c_
LL 40%
d
d
a 30%
20%
70%
No. 4
x
x
Gradation of East Beach and Anaheim Bay Source
U.S. Stantlard Sieve Size
No. IO No. 25 Na. 60 No 120 No 200
r' %x~ x
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Native Beach Sand Grain
Size Envelope ~ +B'
(1997!98 samples)
c
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a
--~ Native ~-24 (58Dj
-Composite Coarse Curve
x Composite Finest Curve
--~ Composite Average
^ Native ~+6 (SBD)
Native Beach Sand Grain
Size Envebpe ~ -24'
(1997198 samples]
05 o.a
10 1 0.1 0.01
' Composite Oata cons~su of only the approach
Grain Size (mm) channel data, mcluMng 18, and extlurLng Te
Figure 9 -Existing Sand Gradation at East Beach
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Justification far Reassessment of 14
Beach Maintenance Federal Cost-Sharing Agreement
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\tOFFATT & NICHOL
3.4 Beach Profile
Elevation -The summer beach elevation at East Beach is generally 15 feet MLLW,
except on the far west end next to the pier, where the beach elevation is higher (16 to
17 feet MLLW). The toe of the retained East Beach profile is essentially held in position
at the seaward end of the groin at a water depth of approximately -12 feet MLLW.
Beach Profile and Slope -Existing beach profile conditions wen: determined from full
beach profile surveys conducted by the surveyor Dulin & Boynton, Licensed Surveyors
on February 3, 1999. More recent full profile surveys have not been completed, but this
survey is representative of existing conditions as observed on-site through mid-2007.
Beach profiles at East Beach are shown in Figure 10. The steepest portion of the
profile slopes at approximately 1:10 as a function of the existing coarse rained sand on
East Beach. The Gosure depth is at approximately -30 feet MLLW.
Beach Width -The minimum width from the boardwalk out to mean sea level was
approximately 250 feet at Dolphin Street and 440 feet nearest the pier groin on the day
the survey was taken. While these widths appear sufficient to prevent storm damage,
they are significantly reduced in winter, and wave runup is still able to overtop the beach
at the narrowest point between Dolphin and 13"' Streets during certain combined winter
high wave and high tide conditions. East Beach has been overtopped by waves and
been substantially flooded when the dike is not present. The last time this occurred was
on September 25, 1997. Personal observations by Moffatt 8 Nichol (Chris Webb) on
that day indicate that wave overtopping of East Beach, when the dike is not present, is
the result of the level beach area (referred to as the beach berm in coastal engineering,
not to be confused with the winter dike) lying too low relative to wave runup elevations
during winter storm wave conditions.
4. Beach Nourishment
This section presents information about flooding episodes, nourishment history as well
as analyses of various beach nourishment scenarios.
4.1 Flooding Eaisodes
Coastal flooding typically occurs during winter and spring months along East Beach
(see Figure 6). However, flooding has been documented in the month of September on
at least one occasion (see Figure 7). After significant coastal flooding occurred in 1983,
the City hired the consulting firm, Moffatt and Nichol, to wnduct a study. The study was
titled the Winterization of Seal Beach (1984) and its purpose was to analyze coastal
flooding issues at Seal Beach and provide recommendations for both short-term and
long-term solutions that address residents concerns.
Justification for Reassessment of ~ 5
Beach Maintenance Federal C;ostSharing Agreement
~r
® ~~
MOFRATT & NICH01.
24 , ~ -~ ,
20 '~ ~ ~ 'PROFILE .1 • (Dolphin!Street) '
16.--~ _ ~ - ; PROFILE 2 (13~':Street) ,
t2.-_. _- ~ _ ~~ '~ `- ~',-, _ ~ 11th~Street
40 ~ I ~ \~ ~ - ; ~ .i ;PROFILE 4 '(Pier Groin) •
' - ~ - -/, _
-16 __ _-
-20
-24
-30
too o too 200
GRAPHIC SCALE
W FEET
Figure 10 -Beach Profiles Surveyed on February 3, 1999
Justification for Reassessment of 16
Beach Maintenance Federal Cost-Sharing Agreement
'`~ ~' ~
;~IOFFATT & NiCHOL
According to the Winterization Report, the ideal long-term solution would entail
nourishing East Beach with 5,000 CY of coarse grained sand per year to maintain the
beach, constructing the existing berm seaward 100-feet, lengthening the groin structure
next to the pier and maintaining it, building a winter sand dike annually, and establishing
a survey program to monitor the volumetric changes of the beach profile.
The City explored all the recommendaiions of the report. Lengthening the groin was
deemed the most infeasible of the recommendations due to prohibitive construction
costs, public opposition, and permitting constraints. Because of the City's susceptibility
to coastal flooding, however, officials had to take an active beach management
approach to protect both private property and public infrastructure. Rather than
constructing a seawall or other hard coastal structure the City adopted a soft
engineering solution, whereby the City constructs a winter dike. In November of every
year, the City takes beach sand that accumulates next to the groin and places it
landward to construct this protective dike. Then, near the end of the following spring
heavy equipment removes the dike and restores the beach to its more natural beach
profile.
In 2003, the City of Seal Beach commissioned Moffatt 8 Nichol to study the
effectiveness of the winter dike in protecting the city from flooding. The study concluded
that the seasonal dike at East Beach provides protection for winter wave events up to
the 5-year recunence interval. The study also found that overtopping rates fora 5-year
storm event are 5 to 10 times higher for the beach without the dike present. For a
10-year winter wave event and beyond, coastal flooding would likely occur with or
without the dike. This is primarily because the elevation of East Beach is too low relative
to maximum wave run-up elevations and has insufficient beach volume to provide
adequate protection from wave run-up.
4.2 Nourishment History
Historically, only sporadic replenishment of East Beach has occurred. Table 1 shows
the nourishment history at East Beach. Maintenance dredging at the mouth of the San
Gabriel River, Anaheim Bay, and the Santa Ana River, and backpassing from West
Beach created periods of higher nourishment followed by long periods of minor or
no nourishment. Material resulting from the maintenance dredging is often fine sand
and is therefore quickly carried offshore. This allows the beach to erode to
dangerously low levels and become too low and narrow to provide adequate storm
protection. Consequently, the winter dike is subjected to wave attack and
overtopping.
Justification for Reassessment of 17
Beach Maintenance Federal C.ostSharing Agreement
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D10FFaTT & NICHOL
SUMMARY OF ARTIFICAL NOURISHMENT FROM 1959-1998`
FACT RFACH_ ORANGE COUNTY. CALIFORNIA
QUANTITY OF
YEAR MATERIAL PLACEMENT ON SEAL BEACH SOURCE OF MATERIAL CONTRACTING AGENCY
(CU.YD.)
7959 225,000 Wesl and Eest Beaches no di8erenbebon San Gabriel Rlver Clty of Seal Beach
7967 AND 1968 70 000 West and East BeaMes (no dlfrerentlatlon) San Gabnel RWer Los Angeles Flood Control DlstdG
1989 AND 7970 130,000 East Beach West Beech City of Seal Beach
"
1977 AND 1972 33,400 East Beach
1g7q 3,000 East Beach
1975 5,400 East Beech
1976 1,800 East Beach
U.S. Army Corps of Englneere.
1983 250,000 " East Beach Anaheim Bay Los An ales Dlstnct
U.S. Army Corps of EngtneeB.
1988 110,000 East Beach Anaheim Bay Los Angeles Distnct
1995 30 000 East Beach Same Ana River CI of Seal Beach
1998 15,000 Eest Beach Santa Ane River Ciry of Seal Beach
1gg7-lggg 75,000 East Beach Palmdale Ciry of Seel Beach and State DBW
T AL 8 700
' Data based on rernms frwn the U.S Army Carps of Enpineere, Loa Angeles DiserA, the Qty of Saal Beatl[, Departmen[ of ruonc wares, ano mrnrea a rvcnoi.
Thia meledal wee odpinally amended for placement at SudeitleSuneer Beech end a landfill area an the U S Navel Weapons Statbn at Anehelm Bey. The meterlal did rot meet Me necessary
minimum phaykal requlrementa end wea'dlaposetl oP on Seel Beach Approxlmeley 200,000 cu. ytl. were Immedlelely weahed away leaving only about 50,000 cu. yd. In place
Table 1 -Nourishment History at East Beach
Justification for Reassessment of ~ 8
Beach Maintenance Federal Cost-Sharing Agreement
,.., ~
~(
,J `_ .
MOFF:ITT & NICHOL
The City purchases beach fill material if funds are available when the beach becomes
extremely low, narrow, andlor'rf economical purchase opportunities exist. Most recently,
the City obtained sand from projects at the Santa Ana River by the USACE in 1995 and
1996. In 1997-1998, the City imported sand from a quarry in Palmdale, CA. Figures
11, 12, 13, and 14, show East Beach nourishment projects in 1995 and 1997 from
sources at the Santa Ana River and Palmdale, respectively. These sand material
sources were coarse in grain size and much of the sand has remained in the pocket
close to the groin and is actively managed through the City's backpassing program
which occurs approximately every other year. The very coarse grain size of the
Palmdale sand placed as fill in 1997/98 has proven particularly effective. This sand still
remains relatively close to the groin without moving all the way to the San Gabriel River,
deposits high on the beach profile, and forms a visibly different berm (higher and lighter-
toned in color) from native finer sand. As a result, the Palmdale sand is still relatively
easy to track visually and serves as a focus of sand backpassing and dike construction
efforts.
4.3 Analyses of Beach Nourishment Scenarios
The performance of finer-grained sand for beach nourishment and protection may be
relatively poor when considered in light of previous analyses done for similar sediment
in 1996. Seal Beach applied for State funding to implement a project and at that time
analyzed and compared the performance of Anaheim Bay sand with the coarser
Palmdale quarry sand. Figure 15 shows the gradation of the sand from Anaheim Bay
and Palmdale quany as compared with the native East Beach sand.
An analytical spreadsheet tool for beach profile equilibration after nourishment was
employed to predict the width of the beach both after nourishment with the Anaheim
Bay sand and after nourishment with the coarser upland sand. Figure 16 shows that
the initial constructed berm width would be 150 feet using 166,000 CY of Anaheim Bay
sand, and at equilibrium the berm width would be only 14 feet wider than the pre-
construction profile, thus only a small portion of the sand placed would remain within the
profile. For comparison, Figure 17 shows that the initial constructed bens width was 92
feet using 56,000 CY of coarser upland sand, and at equilibrium the bens width would
be 65 feet wider than the pre-construction profile, thus a larger portion of the sand
placed would remain within the profile. The City decided to pursue purchase of coarser
sand using this information and implemented a successful project that is still providing
tangible benefits to this day as evidenced during each sand backpassing and winter
dike construction event.
Justification for Reassessment of 19
Beach Maintenance Federal Cost-Sharing Agreement
.i ~~:
~.1`~
~to~+:-rr & mcHO~
~.~..
v, . .
.;: .
..
>~
K ' _
-
~
o t - s
- .e
fem
~°Ja ems- .
; ~..
~
_
iii,-
w
r #.
.. . .` ~
_.
.. ~ .. .'r
. '• l
w ` ; - .
.. '-.~; .
a q•i
~.{{l
,' '+`t 'i
Figure 11 -Sand Excavation from the Santa Ana River in 1995 by the
USACE Contractor
•~ m . •p• ~ .. .
•Fy j~~- _ a 'e'y+y7~~,'-.°•.i. ~ ~_ s5 rt~y..•tn~ ~ f,)a ~}gD@t'_s a.v- .y.~
. 4 .~ 1. QY. a- ~~{ a ~ _ !.
per.: ..«''~`
.. :d~:~.-~i
Figure 12 -Sand Delivered by Truck from the Santa Ana River and
Spread at East Beach
Justification for Reassessment of 20
Beach Maintenance Federal Cost-Sharing Agreement
~~':y
410FR:1TT & i IICHOL
-,..Rti..
Y. . ~ }•
wed . V. 1 .. '~,~'•
".:1;; .j
4`tJ•• i ~ +• -
r ., ., "~
\' '~' Qy ^A`yr
~\-' ~ .
~ 1 • ~i
' ,
µy .. '~~ ~~mr
N
i ~ ~`°!~ ,~ `ti
`' ~r { ~. i ~~ -i
G~7 rtn^ai °1SS1 ^.... r }~.e, } . ..-2~~ :.fit
Figure 13 -Sand Loaded Onto Trains at Palmdale to be Delivered to East Beach
. .. ~ 3~a '
' ^t• a .. .-
Y,
-q f~ ]
• t ..~' f• .. . ai .~ .
Y5 • , e ~ - '
.q .. p'.~.. * vye t: } ;~ a ~~~r~p. ... '.t. - ~ 4.
~~ -~~~
• •.4 •t. a .~ s ~• '° %nC0..e~-•y-q,+'~' .• ~ {..
.1 ~~: +.:~~' yt~r''1i. 1~e°j/ry' t°a:iy~...1T"~ }. y~
n , w a: - r ?-tom' ~'~'+~j'.~+i •S • - ro r an.... '~' A O~
•~"" ,-.tyt•~..s: •~•.'%~`Y..~,., b,~s '..Y ~11. i'Tte. .39'`iiy ri;,~^~3_='i~yy~~+
• b i . .Yi t'i:
Figure 14 -Sand Delivered by Rail Being Spread and Sampled at East Beach
Justification for Reassessment of 21
Beach Maintenance Federal Cost-Sharing Agreement
®®" ``~1
MOFRATT & NICHOL
Justification for Reassessment of 22
Beach Maintenance Federal Cost-Sharing Agreement
Figure 15 -Previous Gradation Analysis of Sand From Anaheim Bay and From Palmdale
®®~~ v
MOFFATT & NICH01.
Justification for Reassessment of 23
Beach Maintenance Federal Cost-Sharing Agreement
Figure 16 - Equllibrlum Beach Profile for Anaheim Bay Sand
®®~'~
MOFFATT & NICHOL
Justification for Reassessment of 24
Beach Maintenance Federal Cost-Sharing Agreement
Figure 17 -Equilibrium Beach Profile for Coarser Sand (Desert Sand in this Example)
~~~
~fOFFATT & YICHOL
Native beach sediment samples were taken in 1997/1998 and again in 2008 and a grain
size analysis was carried out to facilitate comparison with sand dredged for the USACE
Surfside/Sunset Beach Nourishment Project. Sand compatibility analysis was
conducted with the Surfside/Sunset Beach Nourishment material, located offshore and
southeast of Anaheim Bay. The grain size data from these borings were compared with
the native beach sand grain size envelope to determine compatibility and are illustrated
in Figure 18. The area being considered encompasses Borings DCSS~2, ~3, -48, -49,
-73, -92(A), and -92(B) and is illustrated in Figure 19.
The graph shows the average of the borings has a Dso of 0.25 mm, compared to the
receiving beach Dso of 0.45 mm. Although the offshore sand is finer than the average
beach sediment, it is considered to be within an acceptable grain size envelope and is
determined to be compatible, as well as suitably resistant to westward sand transport
forces.
Gradation oT Fist Beaeh and lMshote Sand Source
us sr~mm aw. sue.
100%
90%
80%
70%
X
m aox
3
3' so%
g
LL ~%
E
6 30%
'~%
70%
e%
Gnln 8 W (mm)
Figure 18 -Gradation Curve of East Beach and Offshore Borrow Site
Justification for Reassessment of 25
Beach Maintenance Federal Cost-Sharing Agreement
10 1 01 0.01
NOFEATT & NICHOL
~/
-xs
Figure 19 -Offshore Borrow Site Borings
t
4
Justification for Reassessment of 26
Beach Maintenance Federal Cost-Shadng Agreement
.~~.-i
~tOFFATT & NICHOL
5. Analysis of 1985 Beach Erosion Control Study
The Beach Erosion Control Study released by the USACE in 1985 sought to review the
Anaheim Bay project with particular reference to Federal and non-Federal cost sharing.
This study concluded that the cost-sharing responsibilities for the USACE Surfside/
Sunset Beach project should remain at 67 percent Federal and 33 percent non-Federal
for project construction and 100 percent non-Federal for maintenance. The East Beach
site is not included as a sand placement area for this project, as it assumed to be
maintained by the City.
The study correctly estimated the required beach replenishment quantity at Seal Beach
to be 12,000 cubic yards per year. The erosion control study states on page 1 that
"reevaluation of the coastal processes and physical impact of navigation structures on
the Seal Beach segment was beyond the scope of this study, as eSorts wen: limited to
file research."The most recent data consulted for the study was an analysis dated June
1978 conducted by the USACE and titled 'Shore Protection Improvement, Design
Analysis for Stage 7 Construction (Surfside-Sunset Beach)'. No additional scientific
analysis was done to support the study's conclusions.
Because the scope of the 1985 USACE Beach Erosion Control Study was limited to a
review of only existing data, the imoortance of beach elevation and required Grain-size
for successful nourishment at East Beach was overlooked. The essential role played by
grain size is highlighted by the 1983 project when 250,000 CY of material taken from
Anaheim Bay and originally intended for placement at Surfside/Sunset Beach and a
landfill area on the U.S. Naval Weapons Station at Anaheim Bay were placed on East
Beach. Of this quantity, approximately 200,000 CY were immediately washed away
leaving only about 50,000 CY in place. Of the material which remained, the bulk was of
a coarser grain size. According to a footnote in the 1985 Study, "The material did not
meet the minimum physical requirements." This means the grain-size of the material
was too fine for beach nourishment - a fact proven by the enormous volume of material
that immediately eroded. This event serves as evidence that finer grained material
cannot withstand the wave climate documented at East Beach. Grain-size analysis for
beach replenishment was not undertaken for the 1985 Study.
A strong testament to the suitability of coarser grained material for East Beach is found
in the 1997 placement of 75,000 CY brought by train from a quarry in Palmdale. This
material had an average grain size of 0.3 mm. Post placement monitoring indicated that
at least 50°~ (and possibly more) of this material remained on the beach 10 months
following placement in an EI Nino year. However, this material cost $16/CY to be
transported to the beach by train and was dependent on using the rail to the beach
through the U.S. Naval Weapon's Station. Post-9/11 security concerns restrict the use
of the rail line used in 1997 and this fact further hampers the feasibility of transporting
compatible inland material in future by rail.
Justification for Reassessment of 27
Beach Maintenance Federal Cost-Sharing Agreement
JtOFRATT & NICROL
The "Beach Erosion and Nourishment" section of the 1985 Study refers to the City's
redistribution of sand (backpassing) as a local maintenance responsibility because the
redistribution was accomplished using sand from West Beach. However, the Study
overlooks the physical aspects of the sand at West Beach and does not incorporate
today's guidelines for a successful nourishment project. A sustainable beach retention
strategy requires that the incoming material will be of a grain size and the placement
footprint will be such that the erosive local littoral processes are optimally withstood.
Because the West Beach material in question will not remain on East Beach, as it is too
fine, and will continue to be lost to West Beach, then the loss/retum cycle by
backpassing will continue without ever maintaining an increased beach width and
elevation.
An additional premise of the 1985 Study was that suitable beach fill material resulting
from the dredging of the Santa Ana River bed would continue to be available to the City
of Seal Beach. However, the USACE no longer conducts dredging of this riverbed so
what seemed like a viable sand source in 1985 is presently (in 2008) recognized as
being no longer feasible. In fad, research of sand sources undertaken in the interim
has indicated that suitable material is not available locally and must be trucked in at
costs negatively impaled by haul distance, cost per cubic yard, and rising fuel costs.
Consideration of an incomplete data set and lack of source material analyses led all
parfies to conclude that the City of Seal Beach could continue to single-handedly
shoulder the cost of maintaining the eroding East Beach.
6. Conclusion
The USACE installed Anaheim Bay entrance channel in the 1940's that caused erosion
at Seal Beach and Surfside Colony. In response, the USACE nourishes
Surfside/Sunset Beach regularly with coarse sand, and installed Seal Beach groin,
giving the maintenance requirement of East Beach and the groin to the City. The
maintenance requirement was based on approximately 12,000 CY or less of sand per
year being lost from East Beach that the City would have to replenish. The USACE
reconsidered this requirement in 1985, and concluded in their Beach Erosion Control
Study to continue to exclude Seal Beach from further nourishment as part of the
USACE Surfside/Sunset Beach projel because the sand loss rate from East Beach
was still 12,000 CY per year or less. The rationale for the conclusion by the USACE is
flawed and not based on an understanding of existing coastal processes.
City projects at East Beach occurring subsequent to the USACE Study indicate that,
while the sand loss rate is 12,000 CY or less, the key component to maintaining the
beach is sand grain size used for periodic renourishment. The most suitable grain size
for maintenance at East Beach is coarse (>0.25 mm) due to its longer retention time on
the teach compared tofiner-grained sand. Beach nourishment with coarse sand is
Justification for Reassessment of 28
Beach Maintenance Federal Cost-Sharing Agreement
p~ f'Z
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~IOFF:ITT & MCHOL
required as a long-term solution to maintain a high beach elevation and wide beach at
East beach, and to enable successful sand management activities. When the elevation
at East Beach drops to +15 feet MLLW, conditions for winter wave overtopping and
expensive coastal flooding are significantly more likely to occur. Beach maintenance at
East Beach is sustainable with routine re-nourishment using coarse sand and through
sand management via backpassing. For this reason, the City should remain pro-active
in its beach management efforts. However, the City needs assistance to pay for
nourishment with the higher quality course rained sand not readily available in the Seal
Beach locality because procuring that material involves higher transportation costs.
Therefore, the City is unable to sustain its beach maintenance requirement assumed in
the original agreement with the Federal govemment.
The following facts have been established about the condition of East Beach:
• The federally constructed Anaheim Bay jetties caused erosion at East Beach;
• The 1959-constructed groin has proved unable to fully mitigate the westward loss
of sand from East Beach; and
• The City of Seal Beach cannot sustain its maintenance obligation due to the high
cost to acquire the appropriate sand.
Given that the USACE n:gularly dredges coarse sand from offshore for the
Surfside/Sunset Beach project, it makes the most financial sense for the City of Seal
Beach to acquire the coarse sand it needs via that project at a cost savings and with
federal assistance. The coarse sandy materials found in the open ocean dredge areas
off Surfside/Sunset Beach an: compatible with the native sediments found at East
Beach and are sufficient to provide adequate shoe: protection. For context, the USACE
adds approximately 2 million cubic yards of coarse sand to Surfside Colony/Sunset
Beach every five to ten years, while East Beach would require approximately 100,000
cubic yams of coarse sand (1/20"' or 5°~ of that required at Surfside) from the same
source at the same interval to be fully protected.
Protection against flooding and property damage, as well as maintenance of the
economic well-being of Seal Beach will best be accomplished by including the City in
the USACE Surfside/Sunset Beach project and giving them the same level of
assistance that other coastal Cities in northern Orange County receive from the Federal
govemment.
Justfication for Reassessment of 29
Beach Maintenance Federal CostShadng /~reement
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,_;;.! ,V
r10FFAT1' & NICROL
7. References
City of Seal Beach. 1991. Informational Memorandum, Overview of Sand
Replenishment and Groin Repair Issues, Seal Beach, Califomia. November 25,
1991.
Moffatt 8 Nichol. 1984. The Winterization of Seal Beach. October 1984.
Moffatt 8 Nichol. 1997. Letter to City Manager Keith Till, Beach Replenishment Project
Sand Sources. July 16, 1997.
Moffatt 8 Nichol. 2003. Winter Sand Dike Assessment Report. September 2003.
U.S. Anny Corps of Engineers. 1985. Seal Beach -Anaheim Bay Harbor, Orange
County, Califomia Beach Erosion Control Study. May 1985.
U.S. Army Corps of Engineers. 2002. Coast of Califomia Storrs and Tidal Wave Study,
South Coast Region, Orange County. December 2002.
Justification for Reassessment of 30
Beach Maintenance Federal CostSharing Agreement