Water Quality Analyses (WQA), No Final Determination of Impairment: Inner Harbor/Northwest Branch, Bear Creek in the Baltimore Harbor

The Inner Harbor/Northwest Branch and the Bear Creek watersheds are located in the Patapsco/Back River region of the Chesapeake Bay watershed within Maryland.  The Inner Harbor/Northwest Branch watershed is within Baltimore City; the Bear Creek watershed is within Baltimore County.  The Inner Harbor/Northwest Branch has a drainage area of 42,000 acres, which consists of the Jones Falls watershed and two subwatersheds that drain directly into the Inner Harbor/Northwest Branch.  Bear Creek, a highly urbanized tidal creek in the Baltimore Harbor, drains a watershed area of approximately 5,900 acres.

The Baltimore Harbor, with its watershed located in Baltimore City and parts of Baltimore, Howard, Anne Arundel, and Carroll Counties was identified on the 1996 303(d) list as impaired by toxic substances, nutrients, and suspended sediments.  In 1998, the impairment listings were refined to include specific impairing substances and increased spatial resolution based on an analysis of bulk sediment contaminant concentrations compared to non-regulatory screening values.  As a result, the Inner Harbor/Northwest Branch (basin code 02130903) was listed for fecal coliform, chromium (Cr), zinc (Zn), lead (Pb), and polychlorinated biphenyls (PCBs).  In 2002 it was listed for biological community impacts.  Bear Creek, a tributary to Baltimore Harbor (basin code 02130903) located in Baltimore County, was included in the 1996 303(d) listing for the Baltimore Harbor.  However, in 1998 the increased spatial resolution led to Bear Creek being identified as impaired specifically for the substances Cr, Zn, and PCBs. 

The report, available below, provides analyses of the data used to determine the Inner Harbor/Northwest Branch and Bear Creek Zn impairment listings and Inner Harbor/Northwest Branch Pb impairment listing.   It also includes recently collected data that indicates that although sediment toxicity is present in the Inner Harbor/Northwest Branch and Bear Creek, the source of the toxicity cannot be attributed to Zn and Pb.  As a result, the analyses support the conclusion that TMDLs for Zn and Pb are not currently necessary.  However, the segments will remain listed as impaired for biological community impacts due to sediment toxicity.

In an attempt to resolve the biological impairment and proceed with total maximum daily (TMDL) development for the appropriate pollutant(s),  MDE is conducting a stressor identification study in the Baltimore Harbor system.  Thus, MDE is deferring the 303(d) listing decision until the study is completed.  The study is anticipated to be completed by late 2005/early 2006.  A TMDL for the nutrient impairment was completed in 2006.


WQAs for Lead in the Inner Harbor/Northwest Branch and Zinc in the Inner Harbor/Northwest Branch and Bear Creek Portions of Baltimore Harbor in Baltimore City and Baltimore County, 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.