LimnoTech Inc.

TMDL support activities for the Anacostia river case study


Courtesy of LimnoTech Inc.

States and EPA are required to establish Total Maximum Daily Loads (TMDLs) for waterways that fail to support their designated uses (e.g., swimming, recreation, aesthetic enjoyment, etc.) under the Clean Water Act. These TMDLs typically establish strict pollutant load limits for municipalities, industries, and other sources such as agriculture.

TMDLs can be challenging and controversial, and they have been disputed in state and federal court by non-governmental organizations. In 2002, EPA established total suspended solids (TSS) and sediment TMDLs for the Anacostia River Watershed in DC that were subsequently challenged in court by Friends of the Earth. In 2006, the U.S. Court of Appeals for the D.C. Circuit ruled that specifying loads on a seasonal or annual basis in these TMDLs failed to satisfy the Act’s requirement that load allocations be expressed on a daily basis. This meant that the TMDLs needed to be revised.

LimnoTech worked with EPA Region 3, DC and Maryland agencies, and the Interstate Commission on the Potomac River Basin (ICPRB), to develop and implement a plan to quantify the TSS TMDLs and subsequent TMDLs for nutrients and BOD on a daily basis. LimnoTech evaluated the previous TMDLs, the underlying monitoring data, and the updated water quality models developed by the ICPRB. A subset of four approaches was applied to different loading sources to develop TMDL allocations that were expressed on a daily basis. EPA approved the revised TMDLs in 2007 and 2008.

In 2009 EPA was sued to overturn the TSS TMDLs. In July 2011, the U.S. District Court set aside EPA’s approval of the TSS TMDLs, providing a summary judgment ruling in favor of the Plaintiffs on the first of four grounds, which was that the TMDL study should have been done to address all designated uses. However, the Court ruled in favor of EPA’s cross-motion for Summary Judgment on the other three grounds of the complaint. These included upholding the manner in which daily loads were expressed, the aggregation of permitted stormwater discharge (i.e., MS4) wasteload allocations, and use of an implicit margin of safety. These rulings reinforce and provide an affirmative precedent for a TMDL development approach that is important to wet weather dischargers and municipal and industrial point sources.

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