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 Lower North Branch Patapsco River (basin code 02-13-09-06), located in Baltimore, Howard, Anne Arundel Counties and Baltimore City, was identified on the States list of WQLSs as impaired by heavy metals (1996 listing), nutrients (1996 listing), suspended sediments (1996 listing), fecal coliform (2002 listing) and evidence of biological impacts (2002 listing). All impairments are listed for the non-tidal streams. This report provides an analysis of recent heavy metals monitoring data, including hardness data. A data solicitation for heavy metals was conducted by MDE and all readily available data from the past five years was considered. The study finds that the applicable aquatic life criteria for heavy metals and the designated uses supported by those criteria are being met in the Lower North Branch Patapsco River except for Herbert Run where a single exceedance of copper was found. Maryland's water quality standards presently include numeric criteria for metals and other toxic substances based on the need to protect aquatic life, wildlife and human health.