Section 303(d) of the federal Clean Water Act (CWA) and the U.S. Environmental Protection Agencys (EPA) 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. This list of impaired waters is commonly referred to as the 303(d) list. For each WQLS, the State is to either establish a Total Maximum Daily Load (TMDL) for the specified substance that the waterbody can receive without violating water quality standards, or demonstrate that water quality standards are being met. Lower North Branch Potomac River (basin code 02141001), located in Allegany County, Maryland, was identified on the States list of WQLSs as impaired by cadmium (Cd) (1996 listing), sediments (1996 listing), nutrients (1996 listing), low pH (1996 listing), fecal coliform (2002) and impacts to biological communities (2002 listing). The information used for listing Cd is suspect due in part to sampling and analysis methods available at the time, and assessment inconsistencies that led to the listing in 1996.