Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings: Lower North Branch Patapsco River

The Lower North Branch Patapsco River watershed is located in the Patapsco River region of the Chesapeake Bay watershed within Maryland.  The watershed covers a portion of Baltimore, Howard and Anne Arundel County and Baltimore City.  The watershed area covers 75,756 acres.

The Lower North Branch Patapsco River (basin code 02130906), located in Baltimore, Howard, Anne Arundel Counties and Baltimore City, was identified on the State’s 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.  Therefore a TMDL for heavy metals is not required for the 8-digit basin, but a TMDL for Cu may be needed in Herbert Run, a tributary of the main branch in the lower most 12-digit basin (basin code 021309061012).  Based on impairment listing methodologies applied by the Maryland Department of the Environment (MDE) further investigation is necessary to determine if Herbert Run is impaired for Cu.  Only one exceedance of Cu was found in six samples, which is insufficient to justify a finding of impairment.  Additional monitoring is necessary to establish whether the exceedance was the result of a single anomalous event or further exceedances will reoccur resulting in an impairment.  However, EPA also believes that MDE’s WQA does not justify the removal of the Herbert Run for lead.  This sub-basin will remain on Maryland’s 303(d) list for further monitoring and future action in the form of a TMDL or WQA. Barring the receipt of any contradictory data, this report will be used to support the removal of the Lower North Branch Patapsco River from Maryland’s list of WQLSs for heavy metals when the Maryland Department of the Environment (MDE) proposes the revision of Maryland’s 303(d) list for public review in the future.  Herbert Run will remain on Part 3 (waterbodies that have insufficient data to define the impairment status) of the 303(d) list  with Cu as the impairing substance.  The nutrient, suspended sediment, fecal coliform and biological impairments will be addressed at a future date. 

WQA of Heavy Metals for the Lower North Branch Patapsco River in Baltimore, Carroll, Howard and Anne Arundel Counties and Baltimore City, MD

(Concurrence January 18, 2005)

EPA's Decision Letter

EPA's Decision Letter

Main Report 


Comment Response Document


Contact Information

Please direct questions or comments concerning this project to Maryland's TMDL Program at (410) 537-3818.