Final TMDLs Approved by EPA: Catoctin Creek

The Maryland 8-digit (MD 8-digit) Catoctin Creek watershed (basin number 02140305) 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 on the east and South Mountain on the west.  The mainstem flows through the Middletown Valley and eventually empties into the Potomac River approximately three miles upstream from Point of Rocks, Maryland. The Catoctin Creek watershed drains an area of 120 square miles, which includes areas of forested mountain slopes, agricultural valleys, and small towns.  Approximately 5% of the total watershed is covered by water (i.e. streams, ponds, etc.).

The Maryland Department of the Environment (MDE) has identified the waters of the Catoctin Creek watershed on the State’s 303(d) List as impaired by sediments (1996), nutrients (1996), bacteria (2004), and impacts to biological communities (2002 and 2006). The designated use of Catoctin Creek and its tributaries is Use IV-P (Recreational Trout Waters and Public Water Supply). The objective of the TMDL established below is to ensure that there will be no sediment impacts affecting aquatic health, thereby establishing a sediment load that supports the Use IV-P designation for the Catoctin Creek watershed. The listings for nutrients, bacteria, and impacts to biological communities will be addressed separately at a future date.

Note: Following the approval of the TMDL it was discovered that the incorrect design flow of 0.15 million gallons per day (MGD) was applied in the calculation of the Process Water Baseline Load for the Middletown East wastewater treatment plant (WWTP). When the correct design flow of 0.25 MGD is used in the analysis, the individual Process Water Baseline Load for the facility increased by 4.6 ton/yr, and as a result the total Process Water Baseline Load for the watershed also increased by 4.6 ton/year. Since the assimilative capacity of the watershed is fixed at 14,370.3 ton/yr, and no reductions were applied to process water sources in the analysis, the individual Process Water wasteload allocation (WLA) for the facility and the total Process Water WLA for the watershed also increased by 4.6 ton/yr. Due to this increase, additional reductions, although minimal and totaling an equivalent 4.6 ton/yr, were required from both the non-point source sector and regulated urban stormwater sector within the watershed. The revised final version of the document containing these updated allocations is available for download below.


Total Maximum Daily Load of Sediment in the Catoctin Creek Watershed, Frederick County, Maryland

(Approved on July 31, 2009)

EPA's Decision Letter EPA's Decision Letter
MDE's Edits to EPA's Decision Letter MDE's Decision Letter Edits (25.5KB)
Revised Final Report TMDL Catoctin Creek final revised.pdf (836 KB)
Final Report TMDL_Catoctin_Creek_final.pdf  (834.6KB)
Comment Response Document CRD_Catoctin_Creek_final.pdf (7KB)

Additional Supporting Information

Using MBSS Data to Identify Stressors for Streams that Fail Biocriteria in Maryland (4775 KB)
A Methodology for Addressing Sediment Impairments in Maryland's Non-tidal Watersheds (361 KB)


Contact Information

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