Environmental Engineering Reference
In-Depth Information
supports the fi nding of just one resident species, spotted sand bass, with residues
above 20 ppb.
Another important issue is the State Board's TMDL listing policy. The policy
requires 6 exceedances for 63 measurements for listing and the initiation of a TMDL
(Table 2-3 in SARWQCB 2006 ). The policy also advises Regional Boards to not
consider migratory (coastal) fi sh because the residues can come from other water-
sheds. This concept would be particularly true for Newport Bay because of coastal
migration of fi sh from the very highly contaminated Palos Verdes Shelf, only 30
miles to the north. With only two composites from one species of resident fi sh in
excess of the guidance, the listing criteria is not met, meaning that a TMDL for
PCBs would not be recommended by the State Board for Newport Bay.
More important than meeting the State Board's listing policy for a TMDL, the
health risks of PCB from ingestion of resident sport fi sh caught in Newport Bay can
be shown to be insignifi cant. The average residue in six composites of spotted sand
bass was 21 ppb. This average assumes PCB concentrations at one-half the detec-
tion limit of 5 ppb in composites where PCBs were not detected. All other residen-
tial sport fi sh species were below 20 ppb, with most being below the detection limit
of 5 ppb. Since sport fi shermen eat several different species of resident fi sh, the
average residue of PCBs ingested will be well below the guidance of 20 ppb. The
average PCB residue in all 63 resident and coastal sport fi sh composites is 12 ppb,
a value below the guidance. In addition, the fi sh residue data are 11 years old or
older, meaning that with no new sources of PCB input and further decay of residues,
exposures are even lower today and will continue to decrease in the future.
7
Summary
DDT, chlordane, toxaphene and the PCBs are persistent organochlorines that are
still found in aquatic environments of Newport Bay and Watershed (Orange County,
California), decades after their use was discontinued. Under the Clean Water Act,
organochlorines are regulated by a total maximum daily load (TMDL) to achieve
levels that protect wildlife and human health. Stakeholders in the Newport Bay
Watershed and an Independent Advisory Panel (IAP) requested by the Regional
Board and administered by Orange County have questioned the quality of the
science used to establish TMDL targets by US EPA Region IX and the Santa Ana
Regional Water Quality Control Board. This review brings together a number of
technical reports written by stakeholder consultants that address the scientifi c basis
for the organochlorine TMDLs for Newport Bay and Watershed.
Urbanization of former agricultural lands has effectively capped soil organochlo-
rine residues, reducing runoff into aquatic environments. Sediment controls have
further reduced the movement of organochlorines from soil to aquatic environ-
ments. Residues in soil, water, sediments and biota are declining. For example,
DDT in red shiner and mussels from Newport Bay and Watershed is declining expo-
nentially with a half-life of 3.8 years and 5.2 years, respectively.
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