Final TMDLs Approved by EPA: Lower Monocacy River

The Lower Monocacy River watershed is located in the Potomac River Sub-basin in Frederick, Carroll and Montgomery Counties, Maryland.  The Lower Monocacy River watershed is situated primarily in Frederick County but includes small portions of Carroll and Montgomery Counties as well.  The watershed covers approximately 3,142 square miles (194,790 acres) and is characterized by a moderately steep to flat terrain.  There is a significant amount of agriculture within the watershed, which consists mostly of row crops, but also includes dairy production.  The watershed contains numerous urban centers including Frederick, the largest city in the watershed, Woodsboro, New Market, and parts of Walkersville and Mount Airy.  The total population within the watershed is estimated to be approximately 96,000.  

The Lower Monocacy River, upstream of US Route 40, its tributary Israel Creek, and the Lake Linganore watershed are designated as Use IV-P waterbodies (Water Contact Recreation and Protection of Aquatic Life, Recreational Trout Waters and Public Water Supply); downstream of US Route 40, the Lower Monocacy River is designated as a Use I-P waterbody (Water Contact Recreation, Protection of Nontidal Warm Water Aquatic Life, and Public Water Supply).  Additional tributaries of the Lower Monocacy River – Ballenger Creek, Bear Branch, Carroll Creek, Furnace Branch, Little Bennett Creek, and Rocky Fountain Run – are designated as Use III-P waterbodies (Water Contact Recreation and Protection of Nontidal Cold Water Aquatic Life, and Public Water Supply). 

The Maryland Department of the Environment (MDE) has identified the waters of the Lower Monocacy River on the State’s 303(d) List as impaired by nutrients (1996) and impacts to biological communities (2002, 2004, 2006).  All impairments are listed for non-tidal streams.  Because scientific research supports that phosphorus is generally the limiting nutrient in freshwater aquatic systems, the 1996 nutrient listing was refined in the 2008 Integrated Report to identify phosphorus as the specific impairing substance.  Therefore, the listed impairment of phosphorus will henceforth be referred to in this report and the term “nutrients” should be read as interchangeable with “phosphorus” in this case.  The document, available below, establishes a phosphorus TMDL for the Lower Monocacy River.

A data solicitation for nutrients was conducted by MDE in November 2009, and all readily available data up to the time of the TMDL development have been considered. A TMDL for fecal coliform and a TMDL for sediment were approved by the US EPA in 2009. The listing for impacts to biological communities will be addressed separately at a future date.  

Total Maximum Daily Load of Phosphorus in the Lower Monocacy River Watershed, Frederick, Carroll and Montgomery Counties, Maryland

(Approved on May 22, 2013)

EPA's Decision Letter EPA's Decision Letter
Main Report

Lower_Monocacy_River_NutTMDL_final.pdf (1,809KB)

Point Source Technical Memorandum

Lower_Monocacy_River_Nut_PS_techmemo_final.pdf (39KB)

Nonpoint Source Technical Memorandum

Lower_Monocacy_River_Nut_NPS_techmemo_final.pdf (18KB)

Comment Response Document

Lower_Monocacy_River_Nut_CRD_final.pdf (241KB)

Additional Supporting Information

Biological Stressor Identification Lower Monocacy River Watershed Report

Lower_Monocacy_BSID_Report.pdf (778KB)

Biological Stressor Identification Methodology

Biological Stressor Identification Methodology (459KB)


Contact Information

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