Section 303(d) of the federal Clean Water Act (CWA) and the U.S. Environmental Protection Agency's (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. 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. The Middle River (basin code 02-13-08-07), located in Baltimore County, MD, was identified on the States list of WQLSs as impaired by nutrients (1996 listing), suspended sediments (1996 listing), copper (Cu) (1998 listing), nickel (Ni) (1998 listing), cadmium (Cd) (2002 listing), and lead (Pb) (2002 listing). All impairments were listed for the tidal waters. The listings for Cu and Ni were based on an analysis using salt water criteria. Code of Maryland Regulations (COMAR) defines the Middle River as a fresh waterbody. A water quality analysis (WQA) of Cd and Pb for the tidal waters of Middle River was performed using recent water column and sediment toxicity data.