3.5 Cultural Resources
portion of which may have been eroded and/or reworked into intertidal sediments during transgression.
Within the region designated for sand dredging, the eastern portion would have the highest probability for
prehistoric site occurrence. Within this high probability zone, it is most likely that prehistoric sites would
be encountered at depths of about nine feet or below, although the depth may be less for portions of the
dredge site moving inshore.
Historical Results
Portions of this proposed borrow site are near generalized shipping zones assessed by an MMS baseline
study as a medium to high probability area for the occurrence of historical shipwrecks.
Within the portion of the dredge area covered by side-scan sonar, several unidentified sonar targets were
detected. They are now known to be scattered rocks deposited by Dr. Jack Patton as part of a reef
R
development experiment. Because they were not re-located they were not monitored or mapped on state
R
sources. Artificial reefs materials have been deposited within the coverage of the geophysical survey grid
R
and adjacent to the dredge site, seen as discrete piles of material in the side-scan sonar image. No side-
scan sonar data area available for the southeast portion of the dredge area (approximately 10 percent).
SO-7
Within SO-7, the water depth varies from 50 feet along the eastern edge of the grid to 80 feet along the
western portion of the grid. At this site, six seismic survey lines were conducted approximately
perpendicular to the beach direction, and ten survey lines were conducted parallel to the beach direction.
A total of 20 vibracores were collected, primarily in the western portion of the grid. The deepest core
penetration was 14.9 feet, in the east-central portion of the grid.
Geoarchaeological Results
Although no offshore archaeological sites are recorded for this area, sites are present both north and south
of the Batiquitos Lagoon entrance along the modern shoreline.
The dredge area at SO-7 can be divided into an eastern inboard and a western outboard portion. When
viewed in a beach perpendicular profile, a distinct change in bottom and sub-bottom reflector slope is
observed midway through the grid. This change in slope may be related to a previous stable sea level
Page 3.5-8
Regional Beach Sand Project EIR/EA
99-69\SANDAG EIREA 3.5 to 3.12.wpd 7/17/00
Previous Page
