1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
to 160 for arsenic. Of those chemicals exceeding chronic LOECs, 4 were evaluated using an
exposure point concentration that was ½ the reporting limit for a non-detect.
Terrestrial Invertebrates
Comparisons for terrestrial invertebrates (Table 4-1) show that chronic NOECs were
exceeded by zinc with an HQ of 1.1, but risk is considered uncertain because a chronic
LOEC was not identified. Chemicals exceeding chronic LOECs consisted of 6 inorganics and
1 organic indicating possible risk (Category B) for these COECs. Those with the highest HQs
included arsenic, barium and chromium, with respective HQs of 5, 45, and 7.8.
Upland Birds
Risk estimates for upland bird species (Table 4-2) indicated that arsenic, cobalt, lead, and
zinc all posed some possible risk to sparrows (Category C). Chromium posed an uncertain
risk (Category U) because a LOAEL was not available). Zinc was the only chemical that
exceeded a NOAEL for kestrels indicating some possible risk (Category C).
Mammals
Risk evaluations for mammals (Table 4-2) indicated that barium and lead posed some
possible risk (Category C) for the mouse and coyote (barium only). Cobalt and vanadium
also posed an uncertain risk (Category U) for the mouse. The NOAEL HQ ranged from
1.2 or lead (mouse) to 52 for barium (mouse). None of the chemicals detected exceeded
available LOAELs.
4.1.2 Sediment/Soil – Aquatic and Semi-Aquatic Receptors
Areas of the Lowlands that were evaluated for potential risks to aquatic and semi-aquatic
receptors consisted of 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. Risk estimates were calculated for aquatic plants, aquatic invertebrates, and semiaquatic
birds (heron, stilt, and tern). The results for chemicals with HQs exceeding 1 are
presented in Table 4-1 for aquatic plants, Table 4-3 for aquatic invertebrates, and Table 4-2
for semi-aquatic birds. The HQs for all detected chemicals are presented in Appendix I,
Tables I-1, I-2, and I-3.
It should be noted that although the sediment bioaccumlation studies using Nereis showed
significantly (P