A Court of Appeal has upheld the Regional Board’s adoption of the total maximum daily load (TMDL) for concentration of pollutants in the sediment in McGrath Lake, rejecting the claim that TMDLs may not be stated in terms of concentrations of pollutants in lake bed sediments. Conway v. State Water Resources Control Board, No. B252688 (2nd Dist., March 30, 2015).

The Clean Water Act requires states to identify polluted water bodies within their jurisdictions, and to set TMDLs for those water bodies. The TMDL is the maximum amount of pollutants that can be discharged into an impaired water body from point and nonpoint sources. California implements the TMDLs in California through the Porter-Cologne Water Quality Control Act.

McGrath Lake is a small, black dune lake located at the southern end of McGrath State Beach Park in Ventura County. It is located within the McGrath Lake subwatershed, which consists primarily of agricultural fields, petroleum facilities, park lands, public roads, and a closed landfill. McGrath Lake was placed on the Clean Water Act Section 303(d) list on of impaired waters in 1998, 2002, and 2006 due to levels of organochlorine pesticides and PCBs.

In 2009, the Los Angeles Regional Water Quality Control Board set TMDLs for the lake through an amendment to the Los Angeles Basin Plan. The Board concluded that exposure of the McGrath Lake ecosystem to the organochlorine pesticides and PCBs in amounts exceeding the objectives and criteria had impaired beneficial uses, including aquatic life and recreational uses. The Basin Plan Amendment set TMDLs for contaminants from two primary sources: (1) agricultural runoff from surrounding fields that entered the lake largely through a Central Ditch; and (2) from lake bed sediment which could enter the lake by, among other ways, through desorption.

The TMDL for sediment was stated in terms of concentrations of pollutants in the sediment, not the concentration of pollutants in the lake’s water column. While setting a goal of 14 years to achieve the TMDL for the lake bed sediment, the Basin Plan Amendment acknowledged that such a goal would not be achieved by natural attenuation, and that capping or dredging would be the possible methods of remediation.
Continue Reading Court of Appeal Sinks Challenge to TMDL for Lake Bed Sediment