Final TMDLs Approved by EPA: Catoctin Creek

The Catoctin Creek watershed is located within the Middle Potomac River Sub-basin in Frederick County, Maryland.  It encompasses the southwestern portion of Frederick County and is framed by Catoctin Mountain to the east and South Mountain to the west.  The mainstem flows through the Middletown Valley and eventually empties into the Potomac River approximately three miles upstream from Point of Rocks.  The Catoctin Creek watershed drains an area of 76,994 acres, which includes areas of forested mountain slopes, agricultural valleys, and small towns.  The primary urban centers are the areas surrounding Middletown and Myersville, and the unincorporated residential areas along Highway 340 near Jefferson.  The population in the Catoctin Creek watershed, based on the 2000 U.S. Census, was 20,700.

The Maryland Surface Water Use Designation in the Code of Maryland Regulations (COMAR) for mainstem Catoctin Creek above alternate U.S. Route 40 is Use III-P (Water Contact Recreation, Protection of Nontidal Cold Water Aquatic Life, and Public Water Supply), and below alternate U.S. Route 40 is Use IV-P (Water Contact Recreation, Protection of Aquatic Life, Recreational Trout Waters and Public Water Supply); tributaries to Catoctin Creek are designated Use III-P.

The Maryland Department of the Environment (MDE) has identified the waters of Catoctin Creek on the State’s 2010 Integrated Report as impaired by nutrients (1996 listing) and impacts to biological communities (2002).  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.

Once approved by EPA, the document, available below, establishes a TMDL for Nutrients (Phosphorus) in the Catoctin Creek watershed.  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 Sediment was approved by 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 Catoctin Creek Watershed, Frederick County, Maryland

(Approved on September 24, 2013)

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

Catoctin_Creek_NutTMDL_fa.pdf (1,333KB)

Point Source Technical Memorandum


Nonpoint Source Technical Memorandum

Catoctin_Nutrient_NPS_techmemo_fa.pdf (18KB)

Comment Response Document

Catoctin_Creek_NutTMDL_CRD_fa.pdf (149KB)

Additional Supporting Information

Biological Stressor Identification Catoctin Creek Watershed Report

Catoctin_Creek_BSID_Report.pdf (700KB)

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.