1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
• Bolsa Bay – Inner Bolsa Bay (Cell IB) and Outer Bolsa Bay (Cell OB)
• Full Tidal – Cells 1, 1A, 3 through 8, 15 through 18, 43, 44, 51, 58, 59, 61, and 62
• Future Full Tidal – Cells 14, 19 through 40, and 63
• Garden Grove – Winterburg Flood Control Channel – Cell 52
• Gas Plant Pond Area – offsite areas downgradient from the former gas plant, south of
Cells 11 and 12
• Muted Tidal plus Rabbit Island – Cells 41, 42, 45 through 50, 53, 55, 60, 66, and 67
• Seasonal Ponds – Cells 2, 9 through 13
The receptors evaluated for terrestrial (e.g., upland) exposures consisted of terrestrial plants
and invertebrates, Belding’s savannah sparrow (or “sparrow”), American kestrel (or
“kestrel”), western harvest mouse (“mouse”), and coyote (“coyote”). Evaluation areas within
the Lowlands that were assessed for potential risks to terrestrial receptors included Future
Full Tidal, Gas Plant Pond Area, Muted Tidal plus Rabbit Island, and Seasonal Ponds.
The receptors evaluated for aquatic and semi-aquatic exposures consisted of aquatic plants,
invertebrates, and fish; black-crowned night-heron (or “heron”); black-necked stilt (“stilt”);
and least tern (or “tern”). The evaluation areas within the Lowlands that were assessed for
potential risks to aquatic and semi-aquatic receptors included Bolsa Bay, Full Tidal, Future
Full Tidal, Garden Grove-Wintersburg Flood Control Channel, Gas Plant Pond Area, Muted
Tidal plus Rabbit Island, and Seasonal Ponds.
4.1.1 Sediment /Soil – Terrestrial Receptors
Sediment/soil from evaluation areas identified above as terrestrial habitat were evaluated
for potential risks to terrestrial receptors. Risk estimates were calculated for terrestrial plants
and invertebrates, as well as upland birds, and mammals. The results for chemicals with
HQs exceeding 1 are presented in Table 4-1 for plants and invertebrates and in Table 4-2 for
birds and mammals. The HQs for all detected chemicals are presented in Appendix I,
Tables I-1 and I-2.
4.1.1.1 Future Full Tidal
Terrestrial Plants
Terrestrial plants were quantitatively evaluated through comparison to RTVs from literature
sources (Table 3-25) as site-specific toxicity values were not derived for terrestrial plants.
Chronic NOECs were only available for a limited number of COPECs, so most of the
comparisons were conducted using chronic LOECs. A summary of HQs exceeding one for
terrestrial plants is presented in Table 4-1. Two chemicals, nickel and selenium, exceeded
chronic NOECs with HQs of 650 and 384, respectively. Comparisons to chronic LOECs
resulted in 17 inorganics and 4 organics posing a possible risk (Category B). The HQs
ranged from 1.9 for 4-nitrophenol to 850 for lead. Of those chemicals exceeding chronic
LOECs, 4 were evaluated using an exposure point concentration that was ½ the reporting
limit for a non-detect.
SAC/143368(004.DOC) 4-3 ERA REPORT
7/31/02