This document, upon approval by the U.S. Environmental Protection Agency (EPA), establishes a Total Maximum Daily Load (TMDL) for mercury (Hg) in Cash Lake located in the Maryland 8-digit (MD 8-digit) Patuxent River Upper Watershed (basin number 02131104) (2008 Integrated Report of Surface Water Quality in Maryland Assessment Unit ID: MD-021311040938-Cash Lake). 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 TMDL of the specified substance that the waterbody can receive without violating water quality standards, or demonstrate that water quality standards are being met (CFR 2010b). The Maryland Department of the Environment (MDE) has identified the waters of the MD 8-digit Patuxent River Upper watershed on the States 2008 Integrated Report as impaired by sediments (1996), nutrients nitrogen and phosphorus (1996), bacteria (2002 and 2008), methylmercury (MeHg) in fish tissue (Cash Lake - 2002), and impacts to biological communities (2006) (MDE 2008). The designated use of the MD-8 digit watershed and a bacteria TMDL for the river mainstem from Old Queen Anne's Bridge Road to the rivers confluence with the Little Patuxent River are scheduled to be submitted to the EPA in 2010. In the 2012 Integrated Report, the listing for impacts to biological communities will include the results of a stressor identification analysis.