HomeMy WebLinkAboutCC AG PKT 2007-11-05 #L
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AGENDA REPORT
DATE: November 5, 2007
TO: Honorable Mayor and City Council
THRU: David N. Carmany, City Manager
FROM: Vince Mastrosirnone, Director of Public Works
SUBJECT: :EAST BEACH SAND NOURISHMENT PROJECT
SUMMARY OF REQUEST:
The proposed City Council action will provide staff with direction to participate with the Army
Corps of Engineers in the stage 12 sand nourishment project, and; authorize the City Manager to
execute a professional services agreement to prepare environmental review documentation for
Alternative 1
BACKGROUND:
Erosion at the beach east of the Seal Beach Pier (East Beach) diminishes its capacity for
recreation and protection of adjacent structures every year. East Beach loses sand which moves
around and over the pier groin, offshore and through the west jetty of Anaheim Bay, at a rate of
4,000 to 8,000 cubic yards per year. As a result, East Beach becomes relatively narrow and low,
as shown in Figure 1 and can be overtopped by storm waves. At the budget workshop meetings
in June 2007, the Public Works Department presented a slide show depicting some of the storm
events in the past where waves have flooded the promenade and damaged residences along our
coast.
As a result of sand transport away from East Beach, the City continues to seek replenishment for
its eroded beach to resurrect a declining beach and to provide improved protection to public
infrastructure, the pier, the public promenade and parking lots, and private residences within the
vicinity. The City has facilitates protection of re~idences directly behind East Beach from winter
storms by constructing a sand dike along the shorefront each winter. The dike is generally
effective, but occasionally becomes overtopped by storm waves.
The City purchases beach fill material, if and when funds are available, when the beach becomes
extremely narrow and/or economical purchase opportunities exist. For example; adjacent
dredging projects implemented by the U.S. Navy and/or the U.S. Army Corps of Engineers,
improvement to the Santa Ana River by the U.S. Army Corps of Engineers in 1995 and again in
1996, and sand from a quarry in Palmdale in 1997-98 all have been beach nourishment projects.
Agenda Item L
EXISTING CONDITIONS:
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Sand grain sizes vary dramatically from East Beach to West Beach. being far coarser at East
Beach. Generally, Seal Beach consists of poorly graded, fine (0.06 to 0.11 millimeters or mm)
silty sand on the deeper, flatter portions of both beaches near the -6 foot mean lower low water
(MLL W) contour and deeper. The higher steeper portions of the beach 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. Sand found off-shore at East
Beach possesses average grain sizes of between 0.3 mm and 0.5 mm due to the high incident
wave energy there. This 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 "clear distinction of sand conditions from one side of the groin to the other.
The finer sand that exists at West Beach tends to be blown by the daily sea breeze towards the
back of the beach and buries palm tree rings and deposits in residential beach front lots as a
nuisance. City efforts are directed at removing this "blow sand" from near the rear property lines
of the homes and from tree rings and placing it elsewhere to abate the nuisance. Sand composing
the finer fraction of the sediment budget represents this blow sand and is an undesirable addition
to the City.
East Beach can hold or retain a certain quantity of sand before it is eventually transported around
the seaward end of the groin to West Beach. One approach to estimating the capacity of East .-
Beach is to fill the groin compartment out to the depth of the seaward end of the groin all along ..
the entire length of East Beach, with an approximate slope of 2:1. This approach yields a
maximum possible fill quantity of 522,000 cubic yards of sand. As the East Beach shoreline
equilibrates after being nourished, sand from the fill area would be transported west around the
groin to West Beach as the shoreline position and profile equilibrate.
APPROACH ALTERNATIVES:
The City is always exploring alternatives for sand nourishment to East Beach. There are
potential dredging projects that may materialize in the future, projects like dredging the San
Gabriel River, the Santa Ana River again, Long Beach Marina, Huntington Harbor, etc. There is
little known about these potential projects right now and questions about timeframes, sand size
compatibility and quantity make it very difficult to gage how successful or useful these projects
may be to the City of Seal Beach. As stated above, when an opportUnistic situation arises, the
City needs to consider the benefits of participation. Currently, there are two such projects that
are available for the City to consider for East Beach sand nourishment.
ALTERNATIVE 1
The first project would coincide with an ongoing project by the U.S. Army Corps of Engineers to
mitigate damage to Orange County coastline caused by construction of Federal navigation and
flood control works in Long Beach and Anaheim Bay. Dredging for renourishment occurs .-
periodically and has occurred since the 1960's. The U.S. Army Corps of Engineers is currently ..
designing Stage 12 which plans on dredging and placing approximately 1.8 million cubic yards
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of nourishment sand on the Surfside!Sunset Beaches. The location of this underwater borrow
site is approximately three miles southwest of East Beach as shown in Figure 2. Seal Beach is
presented with the opportunity to provide nourishment to East Beach working in conjunction
with the Stage 12 U.S. Army Corps of Engineers project.
Analysis was conducted on this sand borrow site for compatibility. Grain size curves of the
borings taken from the site show that this sand is considered to be within acceptable limits for
the grain sizes existing at East Beach and is determined to be compatible. The City has been in
ongoing discussions with the U.S. Army Corps of Engineers and the State Department of
Boating and Waterways working out the feasibility for the City to join this project. To do this,
the City wou!Jl need to secure environmental clearance and obtain all necessary regulatory
permits and do so in time to meet the project bidding schedule of the U.S. Army Corps of
Engineers. Recently, the Army Corps outlined their pre-construction schedule. They plan on
bidding this project around May 2008 with a construction start date of September 2008. If this
option to participate in the off-shore dredging project is selected, then Seal Beach needs to select
an environmental consulting firm to start the environmental clearance process immediately as at
least 6 months is necessary to obtain the needed permits. In anticipation of this tightened
schedule, the staff sent out a Request for Proposals (RFP) for environmental firms to perform the
environmental review process. Proposals were received by two firms with a third firm declining
to submit a proposal. They are Bonterra Consulting and Chambers Group Inc
Working with the U.S. Army Corps of Engineers project is a great opportunity to nourish East
Beach in an efficient, streamlined fashion. Exact costs have not been determined by the Army
Corps at this time and will not be until the U.S. Army Corps of Engineers has bid results. The
current estimate is $5 - $8 per cubic yard. The City would see a large cost savings by partnering
with U.S. Army Corps of Engineers as opposed to doing a similar nourishment project on our
own. The price per cubic yard of sand would be much less with this project as opposed to railing
sand in, which was about $20 per cubic yard for the Palmdale project, or performing our own
dredging project. The City would realize savings on mobilization costs and some of the
permitting costs as well. At the budget meetings in June of 2007, the City reserved $1 million
dollars in the event that participation in this project is deemed necessary. It is projected that
spending this money could provide East Beach with between 100,000 and 200,000 cubic yards of
compatible nourishment sand.
AL TERNA TIVE 2
. .
The second project is a dredging of the Anaheim Bay Entrance Channel. This project is a Navy
Project that is managed by the U.S. ARMY CORPS OF ENGINEERS. Periodically the Navy
has to dredge the inner harbor and the outer entrance channel to a depth suitable for their ships to
enter/exit and dock. The material that is dredged from this location is slated to be placed on the
SurfsidelSunset beaches before the U.S. ARMY CORPS OF ENGINEERS dredges off-shore and
places sand there as outline in Alternative 1. The amount of material that the Navy needs to
remove is approximately 300,000 cubic yards of sand.
The U.S. ARMY CORPS OF ENGINEERS has indicated that should the City of Seal Beach
decide it wants this material for East Beach, then it is available. The Navy needs a dump site for
this sand and the cost is approximately the same if it dumps it on SurfsidelSunset or East Beach. e
This would provide the City with little to no mobilization or material costs at all. Additionally,
considering the Navy needs to perform all environmental reviews and acquire alI necessary
regulatory permits to dredge and place the Anaheim Bay material, they would conduct, and pay
for most of this work.
Recently, the Anaheim Bay dredging site material was sampled and tested for grain size and
compatibility. This material is a fairly fine grain size with the median grain size being 0.11 mm
in diameter. Considering the composite average grain size of all samples provided by the U.S.
ARMY CORPS OF ENGINEERS to the City, approximately 63% of the Anaheim Bay sand is
finer than that yxisting at East Beach. This sand would typically wash offshore or be transported
around the groin to West Beach. This suggests that the balance of 37% of the sand placed from
Anaheim Bay may remain within the profile, but much of it would deposit lower on the profile
than the position of the beach berm, as shown on Figure 3, and would therefore not serve as
visible nourishment for recreation and property protection.
The information so far regarding the material from Anaheim Bay suggests it is only marginally-
compatible for nourishment at East Beach. The sand would provide an immediate benefit with a
wider beach right after placement, but would adjust to a post-construction equilibrium relatively
rapidly due to high energy wave conditions that occur periodically. Moffatt & Nichol, the City's
contracted coastal engineering firm, determined that "the Anaheim Bay approach channel
sediments are too fine for effective and long-lasting nourishment at East Beach." A large portion .-
of the finer sands deposited on East Beach would be transported west beyond the seaward end of _
the groin to West Beach. There, this finer sand would exponentially add to the already existing
blow sand and would be a difficult nuisance to control. Additional maintenance to the beach and
properties in the vicinity of West Beach would be needed.
SUMMARY:
Sand material the city railed in from the quarry in Palmdale 10 years ago was some of the
coarsest sand the City has used for nourislunent. Slightly courser than the material expected to
be dredged from the off-shore site, sand from Palmdale has done a good job nourishing East
Beach and can still be seen today on East Beach. As stated before, the beach is stilI losing this
sand, but the courser material tends to remain on the beach longer. The life expectancy for sand
dredged from the Anaheim Bay site is around 1-4 years while sand dredged from the off-shore
site is expected to help nourish the beach for 5-8 years.
The advantages of Alternative 1 are:
· Immediate opportunity to partner with the U.S. Army Corps of Engineers on their
dredging project saving the City substantial engineering and permitting fees
· Sand particle size from off-shore dredging superior to sand dredged from the bay
· Larger grain sand will be retained longer
· Less future maintenance from migrating sands
· The next opportunity to partner with U.S. Army Corps of Engineers will be 5-7 years
from now
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The advantage of Alternative 2 is:
. Substantially less costly than using off-shore sand
FISCAL IMPACT:
Funds have been allocated by City Council for Fiscal Year 07/08 in the amount of $150,000 to
begin the environmental permitting process. Additionally, $1,000,000 was reserved by the City
Council for a future beach nourishment project. Alternative 1 will require the $150,000 for
environmental permitting and coastal engineering management and will require $1,000,000 from
the City's General Fund to budget in FY 08/09 for sand nourishment. Alternative 2 will require
the $150,000 _for environmental permitting and coastal engineering management plus an
estimated additional $100,000 from the City's General Fund to budget in FY 08/09 for sand
nourishment.
RECOMMENDATION:
Staff recommends the City Council select alternative 1 and participate with the Army Corps of
Engineers in the stage 12 sand nourishment project. It is additionally recommended that the City
Council authorize the City Manager to execute a professional services agreement to prepare
environmental review documentation for Alternative 1.
Prepared By:
~~
avid L. Spitz, P.E ~
Associate Engineer
cO;7
~<;C~
V{nce Mas simone
Director of Public Works
NOTED AND APPROVED:
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c::>-;. "..,
David N. cJany
. City Manager
Attachment: Figure 1:
Figure 2:
Figure 3:
Attachment 1:
Aerial View East and West Beaches
Off-Shore U.S. Army Corps ofEnginccrs dredging location
East Beach profile utilizing Anaheim Bay dredging material
Moffatt & Nichol Report, October 12, 2007
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MOFFATf & NICHOL
3780 Kilroy Airport Way, Suite 600
Long Beach, CA 90806
(562) 426.9551
Fax (562) 424-7489
October 12, 2007
City of Seal Beach
City Hall
211 8th Street
Seal Beach, CA 90740
Attn: Vince Mastrosimone, Director of Public WorkB
Subj: East Beach Nourishment Project, Updated Letter Report of Project Scope
M&N File: 3874-18
Dear Mr. Mastrosimone:
This letter report provides information requested for a future beach nourishment project at East
Beach. The U.S. Army Corps of Engineers (USACE) is going to prepare environmental
documentation for a future project at East Beach. This letter informs the USACE of conditions
at that site for use in analyses of a project. This report presents information below on the
following items:
I. Basic Background - Historical and existing conditions;
2. Project Description and Sketches - Beach dimensions before and after a project (profile,
width, slope, grain sizes, footprints, quantities, nourishment capacity of existing beach);
and
3. The Future Condition - After equilibration of the nourishment project.
1. Basic Background
Seal Beach is located in northern Orange County, California, between the City of Long
Beach and the Seal Beach Naval Weapons Station. Approximately one mile of coastline
lies along the southwest City boundary. The City's beaches serve as major local and
regional attractions. The beaches provide recreational opportunities for residents and
visitors, as demonstrated by the approximately 2,000,000 visitors who come to visit the
beaches last year, and protection for adjacent coastal structures. Substantial economic
benefits to local businesses and the City are derived from the presence of the beach.
Erosion at the beach east of the Seal Beach Pier (East Beach) has diminished its capacity for
recreation and protection to 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 constructs a sand dike or dune along the
shorefront each winter and has occasionally imported sand to replenish the beach as measures to
improve protection. The City continues to seek to replenish its eroded beach to resurrect
declining beach use, provide improved protection to public infrastructure, the pier, the public
~~~~
MOFFATr & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 2
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promenade and parking lots and to help maintain the local economy.
Seal Beach is located within the Seal Beach Littoral Cell of the larger San Pedro Littoral
Cell as shown in Figure lA and forms a pocket beach bounded by the Anaheim Bay west
jetty to the east and the San Gabriel River east jetty to the west as shown in Figure lB. The
beach is divided by a 750-foot long concrete sheet pile groin immediately west of the
Seal Beach Pier. The groin extends to approximately the -12-foot mean lower low water
(MLL W) depth contour. The west segment (West Beach) of Seal Beach is approximately
2,600 feet long and varies in 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 between 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. Coastal flooding occurs primarily in the area between 13th
Street and Dolphin Street. East Beach is an eroding beach and is the study area for this
project.
A 9.5-foot-wide public promenade fronts the seaward side of the beachfront residences
along East Beach with a 16-inch high, concrete-block wall on its seaward edge. Access to
the beach is provided through openings in the wall located near street ends. The openings
are about 10 feet wide and extend seaward from the wall approximately 8 feet The promenade
wall has small weepholes which allow drainage of water from the beach towards the streets.
The wall is currently deteriorating as evidenced by the crumbled concrete observed during
previous site visits. There are also several palm tree planters on the beach.
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Generally, Seal Beach consists of poorly graded, fine (0.06 to 0.11 millimeters, or mm) silty
sand on the deeper, flatter portions of both beaches near the -6 foot MLL W contour and
deeper. The higher steeper portions of the beach 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 the West Beach, however sand found offshore at
East Beach is very similar in grain diameter to the sand on the higher portions of West Beach.
East Beach sand average grain sizes of between 0.3 mm to 0.5 mm due to the higher incident
wave energy there.
Waves and Sediment SUDDlv
Waves approach the project site 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; 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 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. e
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MOFFATI & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 3
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Figure lA - Location of Seal Beach Within the San Pedro Littoral Cell
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MOFFATf&NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 4
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Figure IB - Vicinity Map
The construction of shore protection and navigation structures northwest and southwest resulted
in changes to the littoral processes in the vicinity of 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. In addition, 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.
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MOFFATT & NIClIOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 5
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Figure 2 - Wave Exposure at Seal Beach
Wave Reflection. AmDlification. and Longshore Sediment TransDort
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 eastern segments of East Beach and West Beach. Additionally, the Anaheim
Bay western jetty has resulted in a local increase in westerly sand transport at the eastem
end of East Beach. This increase is attributed to reflection of wave energy off the Anaheim
Bay western jetty. 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 reflected and
incident waves. Photograph 2 shows the amplification of wave energy in the vicinity of 13th
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 farthest landward position of the MLLW contour lies between 13th and Dolphin
Streets, while the areas adjacent to the San Gabriel River and the Anaheim Bay west jetty
are consistently wide beaches. According to a previous sediment budget analysis, East
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MOF11A.'t'T & mellOr.
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 6
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Figure 3A _ Wave Reflection Toward East Beach, Photograph 1
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Figure 3B _ Wave Amplification at 13th and Dolphin Streets, Photograph 2
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MOFFATf & NICHOl,
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 7
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 per year (Moffatt & Nichol
Engineers 1984). The USACE presents a sediment budget showing a slightly greater loss of
8,000 cubic yards of sand per year shown in Figure 4 (USACE 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. Figure 5
shows the location of wave amplification at East Beach and the resulting direction of net
longshore sediment transport. 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 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. The dike
is generally effective, but occasionally becomes overtopped by storm waves. Figure 8
shows the existing winter dike.
Sporadic replenishment of the cell from maintenance dredging from the mouth of the San
Gabriel River and Anaheim Bay, and backpassing from the West Beach have created
periods of high nourishment followed by long periods of minor or no nourishment. The
material from the maintenance dredging is often fme sand and is therefore quickly carried
offshore. This allows the beach to erode to dangerously low levels where the dike is subject
to wave attack and overtopping. Construction of the dike reduces a large useable beach
area and restricts the resident's view. Severe storm waves have flooded the
promenade and damaged residences in the past.
The City also purchases beach fill material if funds are available when the beach becomes
extremely narrow and/or economical purchase opportunities exist, such as previous adjacent
dredging projects implemented by the U. S. Navy and/or the USACE, improvement to
the Santa Ana River by the USACE in 1995 and again in 1996, and sand from a quarry in
Palmdale in 1997-1998. Figures 9A, 9B, and 10 show nourishment projects in 1995 (Figures 9A
and 9B) and 1997 from sources at the Santa Ana River and Palmdale, respectively. Table 1
shows the nourishment history at East Beach.
Fine sand that exists at West Beach tends to be blown by the daily seabreeze toward the back of
the beach and buries palm tree rings and deposits in residential beach front lots as a nuisance.
City efforts are directed at removing this "blow sand" from near the rear property lines of the
homes and from tree rings and placing it elsewhere to abate the nuisance. Sand composing the
finer fraction of the sediment budget represents this blow sand and is an undesirable addition to
the City.
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Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 10
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Figure 6 - Wave Overwash at East Beach in 1983
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MOFFATf & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 11
Figure 7 - Flooding from Wave Overwash at East Beach in 1997
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Figure 8 - East Beach Winter Dike in 2006
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MOFFAIT&NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 12
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Figure 9A - Sand Excavation from the Santa Ana River in 1995 by the USACE Contractor
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Figure 9B - Sand Delivered by Truck from the Santa Ana River and Spread at East Beach
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~~IiI~
MOFFATf & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 13
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Figure lOA - Sand Loaded Onto Trains at Palmda1e to be Delivered to East Beach
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Figure lOB - Sand Delivered by Rail Being Spread and Sampled at East Beach
~~!!~
MOFFATf&NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 14
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2. Project Description and Sketches
This section presents information of existing conditions at East Beach and potential beach
dimensions after a project, including the beach profile, width, slope, grain sizes, footprints,
quantities, and nourishment capacity of the existing beach.
Existinll Beach Conditions
Beach Profile and Slope - Existing beach conditions were determined from full beach profile
surveys done by the surveyor Dulin & Boynton, Licensed Surveyors on February 3, 1999. More
recent full profile surveys have not been done, but this survey is representative of existing
conditions as observed on-site through mid-2007. Beach profiles at East Beach are shown in
Figure 11. The profile slopes from on~ to off-shore, but the steepest portion of the profile slopes
at approximately 1:10 as a function of the existing coarse-grained sand on East Beach. The
closure depth is at approximstely -30 feet MLL W.
Beach Width - The existing beach width varies along East Beach, being narrower at 13th Street
and wider nearest the groin. The minimum width from the boardwalk out to mean sea level was
approximstely 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, wave runup
stilI overtops the beach at the narrowest point between Dolphin and 13th Streets during certain
combined winter high wave and high tide conditions. Personal observations by Moffatt &
Nichol (Chris Webb, September 25, 1997) indicate that wave overtopping of East Beach appears
to be a result of the beach berm lying too low relative to wave runup elevations during winter
storm wave conditions.
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Sand Grain Sizes - Sand grain sizes vary dramstically from East Beach to West Beach, being far
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 clear distinction ofsand conditions from one side of the groin to the other. Figure 12
shows an envelope of existing sand grain sizes at East Beach with sand being considered from
Anaheim Bay. Data for the Anaheim Bay sand is based on all samples considered together.
Capacity to Receive Sand - East Beach serves the basic purposes !>f providing recreation,
protection to property behind the beach, and "feeding" West Beach with sand. West Beach is
sufficiently wide and does not need more sand. However, feeding West Beach benefits the City
because the excess (surplus) sand can be backpassed to East Beach to widen it and to construct
the winter dike. East Beach can only hold or retain a certain quantity of sand (yet to be
estimated) before it is eventually transported around the seaward end of the groin and/or over the
top of the groin and lost to West Beach. Essentially the toe of retained East Beach profile is held
in position at the seaward end of the groin at a water depth of approximately -12 feet MLL W.
One approach to estimate the capacity of East Beach to receive sand is to fill the groin
compartment out to the depth of the seaward end of the groin all along the length of the beach,
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MOFFATT & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 17
with a profile slope of approximately 20:1 (horizontal to vertical dimensions). This approach
yields a possible fill quantity of 522,000 cubic yards of sand. The orientation of East Beach is
facing southeast toward the direction of the reflected wave off the west Anaheim Bay jetty. As
the East Beach shoreline equilibrates after being nourished, sand from the fiU area would be
transported west around the groin to West Beach as the shoreline position and profile equilibrate.
Similar to tilts approach, the City has employed a strategy to overliU this compartment with sand,
planning for losses to West Beach that can be recycled to East Beach approximately every other
year. This strategy has been successful in protecting East Beach from flooding since September
1997. One factor that has contributed to its success is the very coarse grain size of sand placed
as fill at East Beach in 1997/98. 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. This sand is
therefore is stiU relatively easy to track visually and serves as the basis for backpassing and dike
construction efforts. It represents a suitable situation for the City to manage sand.
3. The Future Condition - Analyses of Potential Beach Nourishment Scenarios
Dredging is planned for the Anaheim Bay Entrance Channel shown in Figure 13 with material
available for nourishment. Figure 12 shows the average grain size of the material being
considered from the outer navigation channel dredging project at Anaheim Bay for comparison
as a magenta line with diamond symbols. The Anaheim Bay material is fairly fine in grain size
with the median grain size being O. 11 mm in diameter. Considering the composite average grain
size of aU samples provided by the USACE to the City, approximately 63% of the Anaheim Bay
sand is finer than that existing at East Beach (at a depth of -24 feetMLLW). This suggests that
the balance of 37% of the sand placed from Anaheim Bay may remain within the profile, but
would deposit lower on the profile than the position of the beach berm and would therefore not
serve as visible nourishment for recreation and property protection.
The performance of the Anaheim Bay sand for beach nourishment and protection may be
relatively poor when also considered in light of previous analyses done for similar sediment in
1996. Seal Beach applied for funds to the State to implement a project and analyzed and
compared the performance of sand from Anaheini Bay with coarser sand from a quarry in
Palmdale. Figure 14 shows the gradation of the sand from Anaheim Bay as being very similar to
the navigation channel sand presently being considered for nourishment. An analytical
spreadsheet tool for beach profile equilibration after nourishment was employed to predict the
width of the beach after nourishment with the Anaheim Bay sand and with the coarser upland
sand. Figure IS shows that the initial constructed berm width would be 150 feet using
166,000 cy of Anaheim Bay sand, and at equilibriwn the berm width would be only 14 feet
wider than the pre-construction profile, thus only a smaU portion of the sand placed would
remain within the profile. For comparison, Figure 16 shows that the initial constructed berm
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MOFFATf & ~lCHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 22
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width was 92 feet using 56,000 cy of coarser sand, and at equilibrium the berm width would be
65 feet wider than the pre-construction profile, thus a larger portion of the sand placed would
remsin 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.
Information provided thus far about sand from the navigation channel outside of the Anaheim
Bay entrance indicates that it is only marginaI1y-compatible for nourishment at East Beach. This
sand could provide a benefit, but it would not remain at East Beach through high energy
conditions before being moved to the nearshore where it would be transported west beyond the
seaward end of the groin that lies at a depth ofapproximately -12 feet MLL W. Coarser sand
than that existing at the outer navigation channel at Anaheim Bay should be considered for
nourishment at East Beach if the project is expected to provide protection for any reasonable
time period (e.g., 5 to 10 years). Alternatively, the City may have to manage the public's
expectations of the performance of the beach fill.
Nourishment Quantity. Footorinl. and Cross-Section
Initial calculations indicate that 522,000 cubic yards of sand could be placed within the East e
Beach compartment between the groin and the Anaheim Bay jetty if the toe of the beach fill
extended seaward to the seaward end of the groin, and the entire beach was within the fill
footprint. Figures 17 and 18 show the plan view of this nourishment footprint, and the cross-
sections of existing conditions and nourished conditions, respectively. The width of the beach
berm immediately after construction is shown as 150 feet, and the slope is 20:1 (H:V) assuming
a construction scenario of work being done by dredging and pumping to the beach. The post-
construction equilibrium cross-section and berm width will vary and depend primarily on the
grain size of the beach fill material.
Elecommendations
We suggest obtaining more information about the grain size ranges of materials to be dredged
from Anaheim Bay to confirm our understanding of the quality of the material if it is to be
considered for nourishment. From information provided to date about Anaheim Bay sand,
results of previous analyses, and the documented processes existing at East Beach we
recommend seeking coarser-grained material for beach nourishment rather than that existing
targeted at outer Anaheim Bay. Coarser-grained material may exist in the open ocean dredge
areas off SurfsidelSunset Beach and are worth pursuing for nourishment.
The City may also wish to consider managing expectations of the public and decision-makers
about the lifespan of a nourishment project at East Beach. This site adjusts rapidly to a post-
constrilction equilibrium profile relatively rapidly after a project due to high energy storm wave
conditions that occur periodically and due to the high angle of wave reflection off the west
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MODATI & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 24
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rFX'STlNG BEACH
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EXISTING EAST BEACH PROFILE
Horizontal Scale 1"=200'
Vertical Scale 1"=50'
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PROPOSED' EAST BEA~
lYPICAL CROSS-SECTI A
Horizontal Scale 1-=200'
VertlCQI Scale 1"=50'
Figure 18 - Typical Existing and Post-Beach Fill Sectlons for East Beach
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MOFFATI&NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 2S
Anaheim Bay jetty that maintains the high net longshore sediment transport rate. Sand from any
project may disperse quite rapidly and need to be managed with backpassing on a regular (annual
or biennial) basis.
Updated Recommendations
At request of the USACE, further review and analysis of the Anaheim Bay proposed dredged
sediment was conducted to identify whether the coarsest deposits seaward of the jetties would
provide suffiiient sand for East Beach. The data collected from the borings in the approach
channel to Anaheim Bay were compared with the native beach sediments to determine
compatibilty. Figure 19 shows the grain size curves of the coarser Anaheim Bay borings in
relation to the grain size envelope of the receiving beach. There are four other borings located
outside the breakwaters at Anaheim Bay that contain fine-grained sediments and do not fit within
the receiving beach grain size envelope; these are not illustrated in the figure. Figure 19 below
shows that only three borings have a Dso coarser than 0.2 mm (DCAB-99-2, -3, and I3a) and
only one of these falls within the preferred grain size range. Furthermore, the composite aversge
of these coarser borings has a Dso of 0.148, which is much finer than the composite for the native
beach sand (Oso approximately 0.45 mm). Most of the borings have grain size characteristics
that are border-line compatible with the native beach sands and would not be expected to be
retained on the beach.
No,'
GradaUon of East Beach ilnd Anaheim Bay Source
U8 1!ItarUIds.v.8lu
_10 Nil. 25 Na III No.120 No ZIO
100%
90%
80%
70%
l
:E 60%
..
~
A' 50%
- ,
.
. ,
Ii: 40% ,
l! ,
J , , ,
Native Beech Sand
30% Grain Sa Envelope <<I
<6'
20%
10%
0%
10
, ,
,
,
.. ..
0.1
Grain Size (mmJ
-NaIIn11-24 (SBD)
-NaIl.... Q+S(SBD)
-II-""",,*,
-DCAB-e8-3
--"""""'..
.........DCAB-98-Bb
-o-OCAB-S&-12a
""""-OCAB-89-181
___DCAB-H-13b
___OCAB-99-3B
.....- Compalllll Avg 01' BorIngl
.. .. .. Campa."- Natrve a_ell
,
,
,
,
,
, , ,
NIlbve B8I.ch 81!1nd Grain
SIzo Envelope 0-2.'
(1997I9B 88rT\ples)
0.01
Figure 19 - Gradation Curve of East Beach and Anaheim Bay Approach Channel
~~!t~
MOWATf & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 26
A plot showing the locations of the various borings is shown in Figure 20 below. The green
solid squares indicate samples that have a Dso greater than 0.2 rom and are considered to be
generally compatible with the native beach sands. The green dashed and shaded squares indicate
the samples that are marginally compatible. The red solid and shaded squares indicate samples
that fit within the native beach grain size envelope, but are too fine for ideal beach nourishment.
The black squares are too fine and are incompatible with the native beach. This illustrates that
there are two good boring locations to obtain coarser material, but they are not located close
enough togeiher to provide a concentrated area of dredging to yield the desired sand, nor would
these isolated pockets provide enough material for a long-lasting beach replenishment project.
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Figure 20 - Anaheim Bay Approach Channel Borings
Further analysis was also conducted using the USACE SurfsideJSunset Beach Stage 12 offshore
sand borrow source site, 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. The area being considered encompasses Borings DCSS-42, -43, -48, -49, -73, -
92(A), and -92(B) and is illustrated in Figure 21. The grain size curves of these borings are
illustrated in Figure 22. The graph shows that the avemge of the borings has a Dso of 0.24 nun,
compared to the receiving beach Dso of 0.46 mm. Although the offshore sand is a finer than the
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MOFFATf & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 27
average beach sediment, it is considered to be within acceptable limits and is deteImined to be
compatible.
o_c
o~t
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Figure 21- Offshore Borrow Site Borings
~~~~
MOFFATf & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 28
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GradaHon of Eat Beach and Offshore Ssnd Source
N~' No. 10
100%
90%
90%
70%
~
~ 60%
..
..
j
~ 50%
~
. ,
Ii: 40% ,
'E ,
!! , ,
. Native Baae Sand Grain
.. 3D% SIze Envelope @ +8'
, (1997196 oampleo)
,
20% , ,
10%
0%
10
US Sl8ndIIdSl.....S..
No 25 Na.6D
No 120 Na 200
, ,
, ,
"
-NoliY8@-24(SBD)
-NoIlv8@+8(SBD)
"
: : -m- DC$S-42.QO
-+-DCSS-4~O
-6- OCSS-48-00
---..- OCSS49-00
--- DCSS-73-QD
"
"
"
- DCSS-ll2-OO
- DCSS-ll2-OO (B)
--.- Compcllllte of Barrow
SIteBorlngl
. .. .. .Compollte of Nabve
Beach Sand"
, ,
"
"
, ,
Nabve Beach Sand Grain
BIze EtMtlopo@-24'
(1997/98 oampleo)
0.1
0.01
e
Gl'llln Size (mm)
Figure 22 - Gradation Curve of East Beach and Offshore Borrow Site
Based on these additional analyses and updated recommendations, the previous
recommendations of this report remain to be the suggested course of action for the City. The
Anaheim Bay approach channel sediments are determined to be too fine for effective and long-
lasting nourishment at East Beach. It is recommended to obtain the coarser-grained material off
SurfsidelSunset Beach for beach nourishment rather than the material from the Anaheim Bay
approach channel. The coarser-grsined material found in the open ocean dredge areas off
Surfside/Sunset Beach are more compatible to the sediments found on the native beach.
Thank you for the opportunity to assist the City and please contact us with any comments or
questions on this letter report. '
Sincerely,
MOFFATT & NICHOL
Chris Webb
Senior Coastal Scientist
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MOFFATT & NICHOL
Vince Mastrosimone
City of Seal Beach
October 12, 2007
Page 29
References
City of Seal Beach. 1991. Informational Memorsndum, Overview of Sand Replenishment and
Groin Repair Issues, Seal Beach, California, November 25, 1991.
Moffatt & Nichol Engineers. 1984. The Winterization of Seal Beach. October 1984.
Moffatt & Nichol Engineers. 1997. Letter to City Manager Keith Till, Beach Replenishment
Project Sand Sources. July 16, 1997.
U.S. Army Corps of Engineers. 2002. Coast of California Storm and Tidal Wave Study, South
Coast Region, Orsnge County. December 2002.