1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
Hazard quotients were developed for two types of comparisons using the indicated equation:
1. Direct comparisons of measured concentrations to media-based effect concentrations
(RTVs) of COPECs in abiotic media. These comparisons were conducted for terrestrial
plants and invertebrates, aquatic plants and benthic macroinvertebrates, and fish.
⎛ Exposure concentration ( mg / kg or mg / L)
HQ =
⎜
⎝ RTV ( mg / kg or mg / L)
⎞
⎟
⎠
2. Comparisons of estimated exposure dosages via the food chain uptake model to effects
dosages (RTVs). These comparisons were conducted for birds and mammals.
⎛ Exposure dosage ( mg / kgbw / d)
HQ =
⎜
⎝ scaled RTVw ( mg / kgbw / d)
⎞
⎟
⎠
The species scaled RTV (or RTV w ) was developed using allometric body weight scaling
methods presented in Sample, et al. (1996) and Sample and Arenal (1999). The scaling
factors applied were of 1.2 and 0.94 for birds and mammals, respectively (Sample and
Arenal, 1999):
where:
RTV
w
⎛ BWt
⎞
= RTVt
⎜
BW
⎟
⎝ w ⎠
RTV t = the RTV for a test species (Tables 3-27 and 3-28)
BW t and BW w = the body weights (in kg) for the test and wildlife species,
respectively, and
b = the class-specific allometric scaling factor.
As depicted in Figure 4-1, the exposure point concentration for each COPEC was compared
to chronic no-effect levels, chronic low-effect levels, and acute-effect levels (where available)
as RTVs for all effects levels were not identified for all receptor groups. Typically, if chronic
no-effect or low-effect levels were available, then acute-effect levels were not identified. One
exception was the values obtained from the California Water Quality Standards (U.S. EPA,
2000), in which both acute and chronic low-effect levels were reported. In general, RTVs for
terrestrial receptors were limited to chronic no-effect and low-effect levels. RTVs for aquatic
receptors included both chronic and acute effect levels. As described in Section 3.1.4.2, the
exposure point concentrations selected for each receptor group were either the maximum
detected value or the 95 th UCL. For some chemicals, the maximum detected value was less
than ½ the maximum non-detect value and the risks were calculated using the ½ non-detect
value (these are flagged with an asterix in the risk tables 4-1 through 4-4). The risk estimates
for each receptor group are presented in the following subsections for each evaluation area
in the Lowlands. As noted earlier (Section 1), the evaluation areas were identified based on
Cells that either currently have or will have similar habitats after the proposed restoration is
completed. These evaluation areas were presented previously, but are listed below for
reference:
1−b
ERA REPORT 4-2 SAC/143368(004.DOC)
7/31/02