1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
questionable. The use of other confirmation techniques, such as gas
chromatography/mass spectroscopy should be considered in the future.
The validated data from the ERA chemical database (including both Tetra Tech and
CH2M HILL samples) were then evaluated for their use in the risk assessment. Data were
retained or eliminated from the ERA database using the following guidelines:
• Media included in the database consisted of field-collected sediment/soil, surface water,
and biological tissue (terrestrial plants, terrestrial and aquatic invertebrates, fish, stilt eggs,
and small mammals) and polychaete worm tissues from the bioaccumulation studies.
• Focused and random sampling sites were included in the database for purposes of data
summarization and to evaluate exposure point concentrations. Data from the dredge
sampling (both surface and deep samples) were also included for purposes of evaluating
site-specific background concentrations (see Section 3.1.3); however, only those data that
were collected from the 0- to 2-foot depth after habitat restoration were included in the
data used for exposure and effects evaluations.
• Chemical results with final validation qualifiers of any letter except "U" or "UJ" were
considered detected.
• Chemical results with final validation qualifiers of "U" (nondetect level or sample
quantitation limit) or "UJ" (estimated nondetect level) were considered nondetects and
were evaluated at one-half the sample-specific reporting limit to calculate summary
statistics and exposure point concentrations. It should be noted that the Tetra Tech data
did not include sample-specific reporting limits. If a chemical was nondetect, then the
value reported was “0.” This resulted in a slight underestimation of some statistical
parameters (e.g., mean and 95th UCL) as a “0” was evaluated rather than one-half of a
small value. (For example, if the sample-specific reporting limit was 0.6, but a 0 was
reported, then the value used in the summary statistics would have been 0 instead of
0.3 [one-half of 0.6]).
• Chemical results with a laboratory or validation qualifier of "R" were considered rejected
and were removed from the database.
• Chemical data for abiotic media were retained for all sampling locations within a
given evaluation area if the chemical was detected at least once in a specific medium.
Chemicals that were never detected in a specific medium were considered not present
and were removed from the database. For example, if chemical “x” was detected in at
least one sediment/soil sample in the Full Tidal area, then chemical “x” sediment/soil
data from all sampling locations were retained. If chemical “x” was not detected in any
of the surface water sampling locations, then it was assumed that chemical “x” was not
present in surface water and all associated data were removed from the database.
• Chemical data for biological media (i.e. tissue) were retained for all sampling locations
If the chemical was detected once within the entire Lowlands. Data were not removed
based on detection/non-detection within an evaluation area because tissue data were
used to calculate bioaccumulation factors for the entire Lowlands.
ERA REPORT 3-8 SAC/143368(003.DOC)
7/31/02