Final TMDLs Approved by EPA: Cash Lake

Cash Lake is an impoundment located within the 12,841 acre Patuxent Wildlife Refuge Research Center in the MD 8-digit Patuxent River Upper watershed, northeast of Washington D.C. in Prince George’s County, Maryland. The total population in the MD 8-digit Patuxent River Upper watershed is approximately 165,898. The watershed draining to Cash Lake covers 1,490 acres. The impoundment, which is owned by the United States Department of the Interior, discharges to a tributary of the Patuxent River Upper. An earthen dam along an unnamed tributary of the Patuxent River Upper was constructed in 1938 for the purposes of recreation and fish and wildlife management. 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 Cash Lake watershed requiring the implementation of Maryland’s antidegradation policy.

The Maryland Department of the Environment (MDE) has identified the waters of the MD 8-digit Patuxent River Upper watershed on the State’s 2008 Integrated Report as impaired by sediments (1996), nutrients – nitrogen and phosphorus (1996), bacteria (2002 and 2008), methylmercury (MeHg) in fish tissue (Cash Lake - 2002), and impacts to biological communities (2006). The designated use of the MD-8 digit watershed Patuxent River Upper mainstem and its tributaries, including Cash Lake, is Use I (Water Contact Recreation and Protection of Aquatic Life).

A Water Quality Analysis (WQA) of eutrophication to address the nutrients (nitrogen and phosphorus) listing was approved by the EPA in 2007, and the watershed was delisted for bacteria in 2002 (relisted in 2008 – mainstem only from Old Queen Anne's Bridge Road to the river’s confluence with the Little Patuxent River). A sediment TMDL for the MD 8-digit watershed and a bacteria TMDL for the river mainstem from Old Queen Anne's Bridge Road to the river’s confluence with the Little Patuxent River are scheduled to be submitted to the EPA in 2010. In the 2012 Integrated Report, the listing for impacts to biological communities will include the results of a stressor identification analysis. 

Total Maximum Daily Load of Mercury for Cash Lake Watershed, Prince George’s County, Maryland

(Approved on March 18, 2011)

EPA's Decision Letter EPA's Decision Letter (121KB)
MDE's Edits to EPA's Decision Rationale MDE's Decision Letter Edits (31KB)

TMDL_Cash_Lake_Hg.pdf (668KB)

Comment Response Document

CRD_Cash_Lake_Hg.pdf (7KB)


Contact Information

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