California Regional Water Quality Control Board, Los Angeles Region

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

New Proposed Listings

• 
  “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

Data Assessment

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.