Final TMDLs Approved by EPA: Upper Monocacy River

The Upper Monocacy River watershed is located in the Potomac River Sub-basin in Frederick and Carroll Counties, Maryland.  The Upper Monocacy River is a free-flowing stream that originates in Pennsylvania and flows 58 miles within Maryland where it finally empties into the Potomac River in Maryland.  The watershed area within Frederick and Carroll Counties covers 156,638 acres.   The Upper Monocacy River watershed encompasses areas within both Maryland and Pennsylvania; however, the assessment unit identified on the Maryland 303(d) list and consequently addressed by this TMDL consists only of the Maryland portion of the watershed, otherwise referred to as the MD 8-digit Upper Monocacy River watershed.  Phosphorus loads generated within the Pennsylvania portion of the watershed as well as the phosphorus load transported via Double Pipe Creek, a tributary to the Upper Monocacy River, are included in the analysis, but will be referred to as upstream loads. 

The Maryland Surface Water Use Designation in the Code of Maryland Regulations (COMAR) for the mainstem of the Upper Monocacy River and tributaries is Use IV-P (Water Contact Recreation, Protection of Aquatic Life, Recreational Trout Waters and Public Water Supply) except for Fishing Creek, Hunting Creek, Owens Creek, Tuscarora Creek, and Friends Creek, which are designated as Use III-P (Water Contact Recreation, Protection of Nontidal Cold Water Aquatic Life, and Public Water Supply).

The Maryland Department of the Environment (MDE) has identified the waters of the Upper Monocacy River on the State’s Integrated Report as being impaired by nutrients (1996) and impacts to biological communities (2002) (MDE 2010).  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 nutrients listing was refined in the 2008 Integrated Report to identify phosphorus as the specific impairing substance (MDE 2008).  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 Upper 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 Upper Monocacy River Watershed, Frederick and Carroll Counties, Maryland 
(Approved on May 7, 2013)

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

Upper_Monocacy_River_NutTMDL_final.pdf (2,940KB)

Point Source Technical Memorandum

Upper_Monocacy_River_Nut_PS_techmemo_final.pdf (31KB)

Nonpoint Source Technical Memorandum

Upper_Monocacy_River_Nut_NPS_techmemo_final.pdf (16KB)

Comment Response Document

Upper_Monocacy_River_Nut_CRD_final.pdf (201KB)

Additional Supporting Information

Biological Stressor Identification Upper Monocacy River Watershed Report

Upper_Monocacy_BSID_Report.pdf (2,245KB)

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.