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Sediment samples collected at the Ash Avenue site show the median grain size (D50) for the
composite sample is 0.195 mm with a fines content of 5% (passing the #200 sieve). However, it
is important to note that over 30% passed the #100 sieve which is 0.149 mm. The highest
percentage of fines is located in the offshore region of the beach profile with 43% fines at
-24 feet MLLW. The Carpinteria Reef exists upcoast and offshore of the beach fill site.
Although a relatively high percentage of fines exist offshore at the site, in order to limit the
volume of fine-grained material which may adversely impact the reef, beachfill with up to 25%
fines is proposed for this site. A cobble sample was also collected indicating that the native
beach has a wide gradation and therefore, should be more likely to accept a wide range of
material.
3.2.2
Design Scenarios
The beach fill material will be placed below the mean high tide line, as a layer over the beach
surface as a berm, or as a sand dike along the revetment or back of the beach as described in
Section 3.1.2. The beach-berm concept is shown in Figure 3-6. A typical berm at the Ash
Avenue beach fill site would be elevated to near +10 feet above MLLW and extended 175 feet
seaward, then sloped at 10:1 (horizontal to vertical) to the water. At this site, the elevation is
limited to +10 feet because the back beach has an elevation of only +10.7 feet MLLW.
3.2.3
Timing and Placement Rate
Placement at the Ash Avenue beach fill site is also limited to Fall-Winter placement (i.e.,
between September 15 and March 15) because of the high use of this beach site during the
summer months.  The rate of sand placement is derived from many factors including
environmental factors, truck access, and seasonal conditions (Table 3.1).
3.3
OIL PIERS
The beach fill site referred to as Oil Piers is located in northern Ventura County along Highway
101 (Figure 3-7). The name Oil Piers is in reference to the recently removed Mobil Oil piers.
The beach is backed by a high rock revetment and a bluff. The Oil Piers site is currently used for
recreational purposes including surfing, swimming, boating, and sunbathing. Historically, Oil
Piers was a well-known surfing spot, however since removal of the piers, this spot is not surfed
as heavily. Beach access is provided along an access road that runs parallel to the Pacific Ocean
and via pedestrian underpasses under Highway 101, from large dirt parking lots.
3.3.1
Proposed Quantity and Quality of Beach Fill Material
The plan view of the proposed Oil Piers beach site is shown in Figure 3-8. The plan shows a
beach fill length of approximately 4,000 feet beginning approximately 2,000 feet south of Punta
Gorda (La Conchita Point). The maximum annual volume of material proposed for this site is
approximately 275,000 cy.
Sediment samples collected at this site indicate the median grain size (D50) for the composite
sample is 0.18 mm with a fines content of 13%. From 24 to 30 feet, the percentage of fine-
grained sand (passing the #200 sieve) ranged from 22 to 69%. Therefore, beach fill with up to
3-4
Moffatt & Nichol Engineers



 


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