Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings: Seneca Creek

Seneca Creek is the largest watershed located entirely within Montgomery County.  The Seneca Creek watershed originates near Damascus in the northwest portion of the County, flowing in a southerly direction through Germantown and Gaithersburg, until it joins the Potomac River near the town of Seneca. Two large tributary systems flow into Seneca Creek. These are Little Seneca Creek and Dry Seneca Creek.  The drainage area of the Maryland 8-digit watershed Seneca Creek is 38,500 acres.

The waters of Seneca Creek (MD basin code 02140208) have been identified on the Integrated Report under Category 5 as impaired by nutrients (1996), sediments (1996), and impacts to biological communities (2002).  All impairments are listed for non-tidal streams.  The 1996 suspended sediment listing was refined in the 2008 Integrated Report to a listing for total suspended solids.  Similarly, the 1996 nutrients listing were refined in the 2008 Integrated Report and phosphorus was identified as the specific impairing substance.  Consequently, for the purpose of the report, available below, the terms “nutrients” and “phosphorus” will be used interchangeably.  The listings for sediments and impacts to biological communities will be addressed separately at a future date. 

Water Quality Analysis of Eutrophication for the Seneca Creek Basin in Montgomery County, MD

(Concurrence September 23, 2009)

EPA's Decision Letter

EPA's Decision Letter

MDE's Edits to EPA's Decision Letter

MDE's Decision Letter Edits  (22KB)

Main Report

WQA_Seneca_Creek_eutro.pdf (582KB)

Comment Response Document

CRD_Seneca_Creek_eutro.pdf (7KB)

Additional Supporting Information

Biological Stressor Identification Seneca Creek Watershed Report

BSID SenecaCreek.pdf (837KB)

Biological Stressor Identification Methodology Report

BSID Methodology.pdf (459KB)


Contact Information

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