Total Maximum Daily Loads of Fecal Bacteria for the Anacostia River Basin in Montgomery and Prince George's Counties, Maryland. Final.

摘要

This document, upon approval by the U.S. Environmental Protection Agency (EPA), establishes a Total Maximum Daily Load (TMDL) for fecal bacteria in the Anacostia River (basin number 02-14-02-05). Section 303(d) of the Federal Clean Water Act (CWA) and the EPAs implementing regulations direct each state to identify and list waters, known as water quality limited segments (WQLSs), in which current required controls of a specified substance are inadequate to achieve water quality standards. For each WQLS, the State is required to either establish a Total Maximum Daily Load (TMDL) of the specified substance that the waterbody can receive without violating water quality standards or demonstrate that water quality standards are being met. The District of Columbia (DC) has developed a fecal coliform TMDL for the tidal Anacostia River, which has been approved by EPA. DCs TMDL assigns an allocation to Marylands portion of the Anacostia River. This allocation is a summed load for both tidal and non-tidal segments of the Anacostia River drainage in Maryland. The pathogen indicator organism used in DCs TMDL analysis was fecal coliform, whereas Maryland, which recently adopted EPAs recommended bacteria indicator organisms (E. coli and enterococci), used enterococci for its bacteria TMDL analysis. MDE performed a correlation analysis between these two fecal bacteria indicators to convert DCs fecal coliform TMDL allocation into Marylands enterococci TMDL. Based on the geometric mean resulting from this analysis, a ratio of 0.34 enterococci concentration to fecal coliform concentration converts DCs fecal coliform TMDL allocation for MD into an enterococci TMDL. This represents accurately the bacteria per acre per year loading rates of both DC and Maryland TMDLs. Although generated using a different pathogen indicator organism, Marylands TMDL was based on the allocation stated in DCs TMDL. Therefore, Marylands proposed TMDLs will meet both Marylands and DCs water quality standards, and will be protective of downstream designated uses under all hydrological conditions.