3.1 Geology and Soils
marine terraces. Los Peasquitos Lagoon is an intermittent tidal lagoon due to occasional lagoon closures
from sediment accretion at the channel inlet.
The Torrey Pines receiver site is situated within the Oceanside Littoral Cell and is sub ject to similar
transport processes as described for South Oceanside. According to the CCSTWS, the Torrey Pines
receiver site is not located within a critical erosional area.
Mission Beach
The Mission Beach receiver site is located on a low tide terrace. The existing receiver site comprises the
flat, shallow part of the shoreline visible during high and low tides. The receiver site was once a
depositional area of the ancestral San Diego River. The Mission Beach receiver site is situated within the
Mission Beach Littoral Cell.
Imperial Beach
The Imperial Beach receiver site is located on a low tide terrace. The existing receiver site comprises the
flat, shallow part of the shoreline visible during high and low tides. The receiver site is a depositional area
of sediment from the Tijuana River. The Imperial Beach receiver site is located within the Silver Strand
Littoral Cell.
Borrow Sites
3.1.2
Marine geophysical surveys and vibracore investigations were conducted along the San Diego coastline
to map the horizontal and vertical extent, and compute the volume, of beach-quality sand at nume rous
possible borrow sites. The marine geophysical surveys included the use of side-scan sonar to produce
maps that show the type and extent of the surface (e.g., silt, sand, gravel, cobble) and natural(e.g., bedrock
exposures) or cultural features (e.g., boats, pipelines) on the seafloor. Sediment layers were mapped at 10
feet and 30 feet below the seabed. The borrow sites were defined originally in large rectangles for
purposes of investigation. Over time, dredge areas have been defined within the original rectangle. The
description below pertains to the original site so the dredge area shown in Figures 2-15 through 2-20
represent a smaller subset of the described area.
Regional Beach Sand Project EIR/EA
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