1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
copper were detected in all five stilt egg samples. Other metals were detected with much
lower frequency. Terrestrial plant tissue also had high metal detect frequencies. Almost all
small mammal tissues had metal detects. Mercury, cobalt, and cadmium were the only
metals not found in every sample. Several metals were detected in aquatic invertebrate
samples, with only a few being detected in less than 50 percent of samples.
Pesticides in sediment/soil were low except for 4’4-DDE and 4’4-DDD. Stilt eggs had a high
number of detects for BHC-beta, dieldrin, 4’4-DDT and 4’4-DDE. Aldrin was also detected
in small mammal tissue in 9 of 12 samples.
PAHs and semi-volatiles were detected in various media, but numbers of detects were low.
Waste oil was found in 54 percent of sediment/soil samples.
Seasonal Ponds
Metals, pesticides, PAHs, and semi-volatiles were all found in the Seasonal Ponds area.
Metals were detected in high numbers in sediment/soil samples. Surface water samples
were found to contain some metals although detection was infrequent in most cases. Copper
and zinc, however, were found in all samples. All metals except nickel were found in all
three stilt egg samples. Terrestrial plant tissue was also found to contain several metals.
While sample size for small mammals is only two, the frequency of detection for metals was
almost always 100 percent.
Pesticide detects were relatively infrequent in the seasonal ponds except for 4’4-DDE in
sediment/soil (25 of 49 samples).
Both PAHs and semi-volatiles were detected, but frequencies were low.
Surface water samples had TPH-diesel and waste oil detects in 100 percent of the samples.
3.1.3 Background Evaluation
An evaluation of inorganic constituents in onsite sediments was conducted for the Bolsa
Chica Lowlands. This evaluation was intended to establish the background (ambient) levels
for metals, as described below. Normally, a background evaluation is conducted by a
statistical comparison of the levels of inorganic constituents from samples collected on site
to a body of data representative of local conditions but which are unaffected by site-related
activities (Cal/EPA, 1997). The background values were used in evaluating potential sources
and spatial distribution of COPECs (Section 3.1.4.1) and for developing site-specific sediment
toxicity values using regression analyses (Section 3.2.1.3). They will also be used in the future
to assist in the development of cleanup goals, which will be part of a separate deliverable.
They were not used to screen out chemicals in the COEC selection process. Specifically, all
detected chemicals were taken through the risk screening process to determine COECs.
Chemicals were not excluded from the risk screening based on comparisons to background.
Given the unique ecological and geologic conditions associated with the Bolsa Chica
Lowlands, the Technical Committee decided that the background evaluation would be
based entirely upon analysis of sediment samples collected onsite. To complete the
background evaluation for the Lowlands, the analytical results from the sediment samples
associated with the ERA Sampling and Analyses (including samples from the proposed
ERA REPORT 3-12 SAC/143368(003.DOC)
7/31/02