1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
The field sampling program is described briefly in this section, and sample collection
locations are shown in Figures 3-1, 3-2, and 3-3. A detailed description of the field sampling
is included in Appendix A and core logs for each sampled location are presented in
Appendix B.
3.1.1.1 ERA Sampling and Analyses
The information collected in the field from the ERA sampling program, along with results of
toxicity and bioaccumulation tests conducted in the laboratory, were used to complete the
EEC Report (CH2M HILL, 1999). ERA Sampling was conducted in areas away from known
or suspected sources of contamination (described as random sampling) and in selected areas
where previous studies identified elevated levels of chemicals or contamination (described
as focused sampling). In addition, toxicity and bioaccumulation bioassays were conducted
using site-collected sediment and surface water from random and focused sites, and fieldcollected
biota were analyzed.
Random sampling was conducted throughout the Lowlands at a density of one sample
location for each area of approximately 4 acres, with at least one sample point located in
each Cell. Samples from up to six contiguous areas within the same Cell were combined to
form a composite, stratified by depth. The surface sample included 0 to 6 inches bgs; the
subsurface sample included the combined mid-depth (18 to 24 inches bgs) and bottom
depth (42 to 48 inches bgs) of the core. Sediment/soil from the expected dredging depth to
2 feet below that depth was sampled and analyzed to determine whether any chemicals
found there are likely to be toxic or to bioaccumulate in exposed organisms. No significant
deviations from the sampling program occurred during sampling activities. Small
adjustments were made in the field to accommodate sample collection (e.g., moving a
sampling location if it fell on a physical structure such as a pipe or other solid obstruction to
allow for collection of a sample).
Samples were analyzed for a defined “suite” of analytes. These suites of analytes were used
for three basic purposes:
• To analyze the sediment/soil (Suites A, B, and C), water (Suite D), and tissue (Suite E)
matrices for contaminants as required for ERA purposes (see Appendix A, Table A-2)
• To furnish contaminant results at low detection limits (Suite C) to ascertain if unknown
contaminants are present that were not covered by the other suites (Suites A and B)
• To confirm that conditions outside the focused sites are suitable for marine organisms. A
detailed Quality Assurance Project Plan (QAPP) was followed during the course of the
sampling and analysis and is included in Appendix C.
Each surface sediment (0 to 6 inches bgs) composite sample was analyzed for a low
detection limit suite of analytes (Suite C). All subsurface sediment (> 6 inches bgs)
composite samples were analyzed for either Suite A or Suite B analytes. Of the random
sampling sites, 24 were selected for sediment and pore water toxicity bioassays, and 10 of
those sediments were also submitted for laboratory bioaccumulation tests. Surface water
ponded in Cells was collected and submitted for Suite D analyses as well as toxicity
bioassays. The random sampling program included a total of 277 core locations generating
158 samples of sediments for analyses (92 for Suite A, 66 for Suite C). A summary of the
ERA REPORT 3-2 SAC/143368(003.DOC)
7/31/02