DRAFT – 11/19/01
California Regional Water Quality Control Board, Los Angeles Region
Tissue, Sediment and Benthic Infauna Data
McGrath Lake (Estuary)
Summary of Proposed Action -
“Not Supporting” (Impaired) for benthic infaunal community due to community assessments.
-
“Not Supporting” (Impaired) for PCB in sediment due to exceedances of Effects Range-Median (ERM) and/or Probable Effects Level (PEL).
-
“Not Supporting” (Impaired) for dieldrin in sediment due to exceedances of ERM and/or PEL.
New Proposed Delistings -
Delist total pesticides in sediment because individual chemicals can be listed for exceedances of ERM or PEL as appropriate
These actions all affect the aquatic life beneficial uses.
Table 1. 303(d) Listing/TMDL Information
Waterbody Name |
McGrath Lake Estuary
|
Pollutants/Stressors
|
See Above
|
Hydrologic Unit
|
403.11
|
Source(s)
|
Historical use of pesticides and lubricants, stormwater runoff and aerial deposition from agricultural fields.
|
Total Waterbody Size
|
18.7 ac
|
TMDL Priority
|
25
|
Size Affected
|
|
TMDL Start Date (Mo/Yr)
|
2004
|
Extent of Impairment
|
|
TMDL End Date (Mo/Yr)
|
2007
|
Watershed Characteristics
{Insert text describing the watershed – could be taken from WMI chapter or draft TMDL documents}
McGrath Lake: McGrath Lake is a small brackish waterbody located just south of the Santa Clara River. The lake is located partially on State Parks land and partially on privately-owned oilfields in current production. A number of agricultural ditches drain into the lake. A state beach is located off the coastal side of the lake. The habitat around the lake is considered to be quite unique and it is utilized by a large number of overwintering migratory birds.
Water Quality Objectives Not Attained
Sediment toxicity, benthic infaunal community, ERM/PEL sediment guidelines
Beneficial Uses Affected
Aquatic Life
Sed Tox (93, 94, 98)
Sed (93, 96): chlordane, DDT, dieldrin
Sed (98): chlordane, DDT, PCB, dieldrin
Degraded benthic infaunal community
Table 2. Summary of Sediment and Benthic Infauna Data for McGrath Lake (Estuary)
Dates of Sampling
|
1/13/93
4/13/94
6/19/96
October 1998
|
Number of Samples (n)
|
1993: 1 (sediment)
1994: 3 (sediment)
1996: 1 (sediment)
1998: 11 (sediment)
|
Minimum Data Value
|
Total chlordane: 10 ppb
Total DDT: 150 ppb
Dieldrin: 0.5 ppb
Total PCB: 14 ppb
|
Maximum Data Value
|
Total chlordane: 816 ppb
Total DDT: 3488 ppb
Dieldrin: 38.1 ppb
Total PCB: 448 ppb
|
Median Data Value
|
|
Arithmetic Mean Value
|
|
Standard Deviation
|
|
Number (Percent) above Objective
|
Sediment toxicity: 12 (81 %)
Benthic infauna: 11 (100 %)
Chlordane: 13 (100 %)
DDT: 13 (100 %)
Dieldrin: 10 (77 %)
PCB: 7 (54 %)
|
Potential Sources
Historical use of pesticides and lubricants, stormwater runoff and aerial deposition from agricultural fields.
References
McGrath Lake characterization study conducted by California Department of Fish and Game on behalf of the LA Regional Board (1998).
Bay Protection and Toxic Cleanup Program database.
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