Final TMDLs Approved by EPA: Lower North Branch Patapsco River

The Patapsco River Lower North Branch watershed comprises the downstream portions of the nontidal Patapsco River, located in the Patapsco River sub-basin of the Chesapeake Bay watershed.  The watershed covers 118 square miles and is located within portions of Baltimore, Howard, Carroll, and Anne Arundel Counties and Baltimore City.  There are no “high quality,” or “Tier II”, stream segments (Benthic Index of Biotic Integrity (BIBI)/Fish Index of Biotic Integrity (FIBI) aquatic health scores > 4 (scale 1-5)) within the watershed requiring the implementation of Maryland’s anti-degradation policy.  Also, approximately 0.1% of the total watershed area is covered by water (i.e., streams, ponds, etc.). The total population in the Patapsco River Lower North Branch watershed is approximately 289,886.

MDE has identified the waters of the Patapsco River Lower North Branch on the State’s 2010 Integrated Report as impaired by metals – Chromium, Arsenic, Cadmium, Copper, Mercury, Nickel, Lead, Selenium, and Zinc (1996), metals – Lead and Copper (2006 – Herbert Run), sediments (1996), nutrients - Phosphorus (1996), bacteria (2002 and 2008), Polychlorinated Biphenyls (PCBs) in fish tissue (2008), chlorides (2010), sulfates (2010), and impacts to biological communities (2006). The designated use of the Patapsco River Lower North Branch and its tributaries is Use I (Water Contact Recreation, and Protection of Nontidal Warmwater Aquatic Life), except for Brice Run, which is designated as Use III (Nontidal Coldwater).

The TMDL, available below, addresses the 1996 sediments listing, for which a data solicitation was conducted, and all readily available data from the past five years were considered. The TMDL sets the maximum load limit for sediments, and provides load allocations to point and nonpoint sources. The Patapsco River Lower North Branch was delisted for metals – Chromium, Arsenic, Cadmium, Copper, Mercury, Nickel, Lead, Selenium, and Zinc in 2005, metals – Lead and Copper in Herbert Run in 2008, and bacteria in 2004 (relisted for bacteria in 2008).  A nutrient Water Quality Analysis (WQA) and a bacteria TMDL were approved by the EPA in 2009. The general listing for impacts to biological communities was removed due to a stressor identification analysis completed in 2009, and as a result, the 2010 Integrated Report now identifies chlorides, sulfates, and sediments as specific stressors impairing aquatic life.

Total Maximum Daily Load of Sediment in the Patapsco River Lower North Branch Watershed, Baltimore City and Baltimore, Howard, Carroll, and Anne Arundel Counties, Maryland

(Approved on September 30, 2011)

EPA's Decision Letter EPA's Decision Letter 
(Does not include MDE's requested revisions)
MDE's Edits to EPA's Decision Letter MDE's Decision Letter Edits (35KB)
Main Report PatapLNB_Sed_TMDL_093011_Final  (2,108KB)
Point Source Technical Memorandum PatapLNB_Sed_TMDL_PS_Tech_Memo_093011_Final (25KB)
Nonpoint Source Technical Memorandum PatapLNB_Sed_TMDL_093011_NPS_techmemo_Final (19KB)
Comment Response Document PatapLNB_Sed_CRD_093011_Final (55KB)

Additional Supporting Information

Biological Stressor Identification Patapsco River Lower North Branch Watershed Report (726KB)
Biological Stressor Identification Methodology (459KB)
Nontidal Sediment TMDL Methodology Report (361KB)
Addendum to the Nontidal Sediment TMDL Methodology Report (23KB)


Contact Information

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