Final TMDLs Approved by EPA: Cabin John Creek

The Cabin John Creek is a free flowing creek that originates in the city of Rockville in Montgomery County, Maryland and flows 11 miles in a southeasterly direction until it empties into the nontidal Potomac River near the towns of Cabin John and Glen Echo. On the way from its headwaters to its confluence with the Potomac River, the creek passes under Interstate 270, through Cabin John Regional Park, under Interstate 495, and under the historic Cabin John Bridge. The Cabin John Creek watershed is located in the Middle Potomac River sub-basin of the Chesapeake Bay watershed within southern Montgomery County, Maryland, just northwest of Washington, DC, and covers approximately 26 square miles. The watershed is bounded by Rockville Pike (Route 355) and Old Georgetown Pike (Route 187) to the east and Falls Road (Route 189) to the west.

The major tributaries draining to the creek’s mainstem are Bogley Branch, Booze Creek, Buck Branch, Congressional Branch, Ken Branch, Old Farm Branch, Snakeden, Branch and Thomas Branch (e.g., Beltway Branch). There are no “high quality”, or Tier II, stream segments (Benthic Index of Biotic Integrity (BIBI) and Fish Index of Biotic Integrity (FIBI) aquatic life assessment scores > 4 (scale 1 – 5)) located within the watershed requiring the implementation of Maryland’s antidegradation policy. Also, approximately 0.03% of the watershed area is covered by water (i.e., streams, ponds, etc.). The total population in the Cabin John Creek watershed is approximately 75,170.

MDE has identified the waters of the Cabin John Creek watershed on the State’s 2010 Integrated Report as impaired by sediments (1996), nutrients – phosphorus (1996), bacteria (2002), chlorides (2010), sulfates (2010), and impacts to biological communities (2006). The designated use of the Cabin John Creek mainstem and its tributaries is Use I-P (Water Contact Recreation, Protection of Aquatic Life, and Public Water Supply).

The TMDL, available below, addresses the 1996 sediments listing, for which a data solicitation was conducted, and all readily available data from the past five years were considered. The TMDL sets the maximum load limit for sediments, and provides load allocations to point and nonpoint sources. A TMDL for fecal bacteria was approved by the EPA in 2007. A Water Quality Analysis (WQA) for eutrophication to address the nutrients/phosphorus listing was approved by the EPA in 2009. The general listing for impacts to biological communities was removed due to a stressor identification analysis completed in 2009, and as a result, the 2010 Integrated Report now identifies chlorides, sulfates, and sediments as specific stressors impairing aquatic life.


Total Maximum Daily Load of Sediment in the Cabin John Creek Watershed, 
Montgomery County, Maryland

(Approved on September 30, 2011)
EPA's Decision Letter EPA's Decision Letter 
(Does not include MDE's requested revisions)
MDE's Edits to EPA's Decision Letter MDE's Decision Letter Edits (35KB)
Body of the Report CabJohn_Sed_TMDL_Final  (2,023KB)
Point Source Technical Memorandum CabJohn_Sed_TMDL_PS_techmemo_Final (23KB)
Nonpoint Source Technical Memorandum CabinJohn_Sed_TMDL_NPS_techmemo_Final (14KB)
Comment Response Document Cabin_John_Sed_CRD_Final (14KB)

Additional Supporting Information

Biological Stressor Identification Cabin John Creek Watershed Report (589KB)
Biological Stressor Identification Methodology (459KB)
Nontidal Sediment TMDL Methodology Report (361KB)
Addendum to the Nontidal Sediment TMDL Methodology Report (23KB)


Contact Information

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