Section 303(d) of the federal Clean Water Act (the Act) directs States 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 to establish a Total Maximum Daily Load (TMDL) of the specified substance that the water can receive without violating water quality standards. The Port Tobacco River was identified on the States 1996 list of WQLSs as impaired by nutrients (nitrogen and phosphorus). This report proposes the establishment of two TMDLs for the Port Tobacco River: one for nitrogen and one for phosphorus. Once the TMDLs are approved by the United States Environmental Protection Agency (EPA) they will be incorporated into the States Continuing Planning Process pursuant to Section 303(e) of the Act. In the future, the established TMDLs will support point and nonpoint source measures needed to restore water quality in the Port Tobacco River. This document establishes Total Maximum Daily Loads (TMDLs) for nitrogen and phosphorus in the Port Tobacco River. The Port Tobacco River is a tributary of the Potomac River, and is part of the Lower Potomac Tributary Strategy Basin. The river is impaired by the nutrients nitrogen and phosphorus, which cause excessive algal blooms and can cause exceedances of the dissolved oxygen standard.