Quantcast Design Scenarios

Custom Search
 
  
 
Sediment samples were collected along two transects at each of the beach fill sites. The samples
were collected on the beach and out to a depth of 30 feet (Figure 3-2) to characterize the native
beach gradation. The samples were analyzed for grain size and the results are contained in
Appendix A. The median grain size (D50) for the composite sample is 0.144 mm, with a fines
content of 13% (passing the #200 sieve). The offshore portion of the profile contains the highest
percentage of fines. The samples taken at depths between 18 and 30 feet ranged from 18 to
39% fines. These existing data indicate a relatively high percentage of fines offshore. Although
these fines exist, sensitive resources (offshore reefs and kelp beds) also exist offshore and
downcoast of the beach fill site. Fine-grained particles tend to settle offshore in the vicinity of
these resources. In order to minimize the volume of fines that may adversely impact the reef and
kelp beds, beachfill with up to 25% fines is proposed at the Goleta Beach fill site.
3.1.2
Design Scenarios
The beach fill material will be placed either below the mean high tide line, as a layer over the
beach surface as a berm, or as a dike along the revetment or back of the beach. One or more of
these design scenarios may be used at the same time depending on site conditions. Beach fill
concepts are described below.
Below Mean High Tide Line
Beach fill will be placed below the mean high tide line if the material is darker colored
and finer grained than the existing beach sand. Sand will be delivered to the beach and
pushed by bulldozers to the water's edge. At low tide, the material will be pushed as far
seaward as possible and left in a low berm below the existing berm so that it can be
reworked by waves during the following rising tide.  The fines will be gradually
winnowed out of the material by waves and currents, carried offshore, and sand will be
left behind.
Beach Berm
Beach fill may be placed as a layer over the existing beach as a berm. The beach-berm
concept at Goleta Beach is shown in Figure 3-3. More discussion of the concept of
design profiles versus natural profile evolution is presented in Section 3.7. The berm
would be a level surface extending a certain distance from the back of the beach toward
the ocean, then sloping gradually into the water. The elevation, width, length, and slope
of the berm will vary for each sand placement opportunity, depending upon the quantity
of material to be placed, its qualities and the condition of the beach at the time. Figure 3-3
shows the maximum proposed berm width over the existing profile (maximum envelope)
for the maximum amount of material at the site (100,000 cy/yr). All projects will fall
within this envelope.
A typical berm at the Goleta Beach site for the maximum volume proposed would be
elevated to near +12 feet above mean lower low water (MLLW) and extended 75 feet
seaward, then sloped at 10:1 (horizontal to vertical) to the water. The length of the beach
fill may extend up to 2,200 feet.
3-2
Moffatt & Nichol Engineers



 


Privacy Statement - Copyright Information. - Contact Us

Integrated Publishing, Inc.