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April 15, 2015  |  Written by Brittany Lewis-Roberts

Court of Appeal Upholds TMDL for Lake Bed Sediment

On March 30, 2015, the Second District Court of Appeal issued its decision in Conway v. State Water Resources Control Board (Mar. 30, 2015, B252688) ___ Cal.App.4th ___, finding that the Regional Water Quality Control Board for the Los Angeles Region (Regional Water Board) can adopt a total maximum daily load (TMDL) for a lake bed as a source of pollutants.

In general, a TMDL allocates to pollutant sources the amount of the pollutant that can (or cannot) be discharged into a water body.  The Regional Water Board established the challenged TMDL for McGrath Lake, a terminal lake that receives agricultural runoff and that is listed as impaired for certain pesticides and polychlorinated byphenyls (PCBs).  The TMDL targeted two sources of pollutants:  the Central Ditch, which carries runoff into the lake, and the lake bed sediment itself, from which pollutants can enter the water column through desorption.  The TMDL for the lake bed is expressed as sediment concentration, and the Regional Water Board set a goal of 14 years to achieve the target concentration levels.  In other words, pollutant loads from the Central Ditch and from lake bed sediment already existing in the lake must meet specified concentrations within the time frame provided.  With respect to the pollutants within the lake bed, if land owners within the watershed do not develop and enter into a memorandum of agreement with the Regional Water Board to ensure compliance with the TMDL, the Regional Water Bard intends to pursue enforcement actions against responsible parties.

Various land owners in the watershed impacted by the TMDL challenged the lake bed sediment TMDL, arguing that the lake bed is not a “receiving water” and that the TMDL unreasonably expands liability for agricultural land owners without regard to the amount of pesticides actually being loaded into the lake.  The petitioning land owners also argued that the TMDL improperly mandated the manner in which compliance could be achieved, in violation of Water Code section 13360, and that the Regional Water Board’s actions failed to comply with the California Environmental Quality Act (CEQA).

The Second District Court of Appeal rejected the land owners’ arguments.  The court explained that the TMDL could be stated as pollution remaining in the sediment and not just in terms of pollutant loads entering the lake because there is no natural outlet from the lake.  Pollutants remain in the lake bed sediment, and the TMDL, therefore, could reasonably be expressed as pollutants remaining in the sediment.  Ultimately, the court found that the Regional Water Board “has broad discretion to choose any reasonable method” for measuring a TMDL, and “[i]t has done so.”  With respect to the other arguments, the court found that the TMDL did not violate Water Code section 13360 because TMDLs do not, by themselves, require any action.  In addition, the lack of available alternatives to remediate the sediment pollution, leaving only one practical means for compliance, does not result in a violation of Water Code section 13360.  The court also rejected the claims that the Regional Water Board had failed to comply with CEQA.

For more information regarding this decision, please contact Brittany Lewis-Roberts at

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