Final TMDL Approved by EPA: Patuxent River Middle Watershed

The Patuxent River is the largest river completely located in Maryland, and the basin lies between two large nearby metropolitan areas Baltimore, Maryland and Washington, D.C. The Patuxent River is comprised of eight separate MD 8-digit watersheds. The Patuxent River Middle watershed is located in Anne Arundel, Calvert, and Prince George’s Counties. The watershed comprises an area located between the 8-digit Upper Patuxent watershed and the Lower Patuxent watershed. The Patuxent River Middle mainstem is tidal throughout its reach, which extends from its confluence with the Patuxent River Lower watershed for approximately 16 miles upstream to the start of the Patuxent River Upper watershed. The watershed is entirely located within the Coastal Plains physiographic region. Coastal Plains is one of the three distinct eco-regions identified in the MDDNR MBSS Index of Biological Integrity (IBI) metrics.
According to the Chesapeake Bay Program’s Phase 5.3.2 watershed model, the total drainage area of the Maryland 8-digit watershed is approximately 55,200 acres, not including water/wetlands. Approximately 650 acres of the watershed area is covered by water. There are three “high quality,” or Tier II, stream segments (BIBI and FIBI aquatic life assessment scores > 4 [scale 1-5]) located within the Patuxent River Middle watershed. Tier II segments require the implementation of Maryland’s anti-degradation policy.
The Maryland Department of the Environment (MDE) identified the waters of the Patuxent River Middle watershed on the State’s 2016 Integrated Report as impaired by multiple pollutants. Table 1 in the main report identifies the impairment listings associated with this watershed.  A data solicitation for sediment was conducted by MDE in March 2016, and all readily available data have been considered.
The TMDL, available below, will ensure that watershed sediment loads are at a level to support the designated uses for the Patuxent River Middle watershed, and more specifically, at a level to support aquatic life. 

Total Maximum Daily Load of Sediment in the Non-Tidal Patuxent River Middle Watershed, Anne Arundel, Calvert, and Prince George’s Counties, Maryland

(Approved on July 2, 2018)

EPA's Decision Letter EPA's Decision Letter (6,884KB)
​Fact Sheet Patuxent_River_Middle_Sed_TMDL_FactSheet.pdf (15KB)
Main Report

Patuxent_River_Middle_Sed_TMDL_final.pdf (1,944KB)

Point Source Technical Memorandum Patuxent_River_Middle_Sed_TMDL_PS_TechMemo.pdf (40KB)
Nonpoint Source Technical Memorandum Patuxent_River_Middle_Sed_TMDL_NPS_TechMemo.pdf (26KB)
Comment Response Document Patuxent_River_Middle_Sed_TMDL_CRD.pdf (15KB)

Additional Supporting Information

Biological Stressor Identification Patuxent River Middle Watershed Report (1,298KB)

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.