1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
CAR Sites
A total of 233 locations were sampled in CAR sites as part of the focused sampling. Most of
these CAR sites were “Plate 1 Schaefer-Dixon Anomalies,” those areas within project
boundaries identified from aerial photographs to be areas of disturbed morphology,
possibly from industrial or recreational activity (Schaefer Dixon Associates, 1991).
All CAR site borings were advanced to 6 feet bgs. Samples from each boring were collected
at three intervals; 0 to 6 inches, 30 to 36 inches, and 66 to 72 inches. The middle and bottom
intervals from each boring were combined into a single sample.
For those CAR sites that were less than 1 acre, two borings were collected. However, if the
CAR site was less than 0.1 acre then the two top samples were composited together and the
two middle/bottom samples were composited together.
One boring was collected for every acre or partial acre for those CAR sites that are greater
than 1 acre. No horizontal compositing was conducted. All top samples were analyzed for
the “modified” Suite C list of constituents (Table A-2), and middle/bottom samples were
analyzed for the Suite B list of constituents.
A detailed list of the CAR sites, the number of locations and samples within each site, and
the analyses performed are found in Appendix A.
Partially Characterized Sites
The Partially Characterized sites are the focused facilities or features sampled by Tetra Tech
(1996) for which some existing data were available (Figure 3-3). The sampling plan for the
Partially Characterized sites was developed using all existing Tetra Tech and CH2M HILL
data matched to the list of facilities and features. Sampling rates, analyses performed and
depths below ground surface were used in determining whether any additional
characterization was needed at a particular focused site. Some facilities and features, such as
the oil wells and the roads and berms, were sufficiently characterized and are not scheduled
for additional sampling until the delineation phase, during which the extent of the
contamination will be identified.
A total of 76 Partially Characterized sites were sampled. Below is an explanation of the
sampling and analysis plan for each type of facility or feature. A list of Partially
Characterized sites for each type of facility or feature can be found in Appendix A. Note that
some samples were previously collected during the ERA Sampling program (CH2M HILL,
1998a). Specific locations, numbers of samples, and analyses performed in the modified
sampling plan are detailed in Appendix A.
Sumps
Most of the sumps defined by Tetra Tech were less than 1 acre. There is, however, one site
that is approximately 3 acres and one site, a settling basin, that is about 5 acres. For those
sites that are 1 acre or less, two cores were collected in each. The other two sites were
sampled at a density of 1 core per acre. There were 29 sumps sampled during the second
phase of sampling.
Each core was bored down to 6 feet bgs. Three samples were collected from each boring
(surface, mid, and bottom). The surface interval (0 to 6 inches) from the first core at each
sump was analyzed for the modified Suite C list of constituents. All other surface samples at
ERA REPORT 3-4 SAC/143368(003.DOC)
7/31/02