Section 303(d) of the federal Clean Water Act (CWA) and the U.S. Environmental Protection Agency (EPA)s 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) of the specified substance that the waterbody can receive without violating water quality standards, or demonstrate that water quality standards are being met. Greenbrier Lake in the Antietam Creek watershed (basin code 02-14-05-02) was identified on the States 1998 list of WQLSs as impaired by nutrients.