1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
Aquatic Invertebrates
There were 4 inorganic and 14 organic chemicals that showed probable risk (Category A) by
exceeding acute toxicity levels (Table 4-3). Chemicals that exceeded both the ER-M and the
LC 50 included fluorene, phenanthrene, and low MW PAHs. The HQs for these chemicals
ranged from 1.0 (phenanthrene) to 367 (fluorene). The HQs for comparisons to the ER-M
tended to be lower than those for comparisons to the LC 50 . The largest difference occurs
with fluorene, for which the ER-M HQ was 6.7 and the LC 50 HQ was 367. This indicates that
the LC 50 s for some chemicals may be overestimated depending on the availability of data.
The HQs for other chemicals exceeding either the ER-M or the LC 50 were all less than 10.
Possible risk (Category B), whereby the ER-L or the LC 20 value for amphipod toxicity was
exceeded, was observed for 9 inorganic and 5 organic chemicals. Both the ER-L and LC 20
were exceeded by nickel, zinc, and chrysene with HQs all below 2. The HQs for these
chemicals were comparable between the ER-Ls and LC 20 s. Other chemicals exceeding the
ER-L included copper, lead, mercury, silver, 4,4’-DDE, benzo(a)anthracene, and dieldrin
with HQs ranging from 1.1 (silver) to 105 (dieldrin). Other chemicals exceeding the LC 20
consisted of beryllium, cobalt, and benzo(b)fluoranthene with HQs ranging from 1.4 (cobalt)
to 7.1 (benzo[b]fluoranthene).
Some possible risk (Category C) was observed for cadmium, benzo(a)pyrene, fluoranthene,
pyrene, and high MW PAHs. These were all based on exceeding the no-effect level (Nereis
NOEC), but not a low-effect level. The HQs for these chemicals ranged from 2.3 (high MW
PAHs) to 102 (fluoranthene). Similarly, several chemicals (1 inorganic and 8 organics)
showed uncertain risk (Category U) since the Nereis NOEC was the only RTV available.
Three toxicity bioassays were conducted using the marine amphipod (Eohaustorius estuarius)
with sediment collected from the ponds downgradient from the former Gas Plant
(Table 3-14). Two samples were significantly different from controls for survival. None were
significantly different for reburial.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicated that metals and pesticides pose the greatest
potential for adverse effects (Table 4-2). The tern was the most sensitive receptor in most
cases followed by the heron. Herons were more sensitive to arsenic and equally sensitive to
cadmium. The stilt was the least sensitive, with only one exceedance for chromium.
Chemicals with possible risk (Category B) consisted of cobalt, copper, lead, zinc, 4,4’-DDE,
and Aroclor 1254 (heron and tern). The NOAEL HQs for these chemicals ranged from 2.9 for
copper (heron) to 318 for zinc (tern). The LOAEL HQs ranged from 1.1 for Aroclor 1254
(heron) to 184 for 4,4’-DDE (tern). Two chemicals, arsenic (heron) and cadmium (heron and
tern), showed some possible risk (Category C), and several chemicals showed uncertain
risks (Category U). The NOAEL HQs for the Category U chemicals ranged from 1.4 for
chromium (stilt) to 663 for selenium (tern).
4.1.2.6 Muted Tidal plus Rabbit Island
Aquatic Plants
Potential risks to aquatic plants were estimated through comparison to RTVs for terrestrial
plants (Table 4-1). Calculation of HQs indicate that potential risks are primarily as a result of
metals and PAHs. Both nickel and selenium exceeded chronic NOECs for aquatic plants
ERA REPORT 4-12 SAC/143368(004.DOC)
7/31/02