Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings: Liberty Reservoir

The Liberty Reservoir watershed is located within the Patapsco River sub-basin of the Chesapeake Bay watershed, within Maryland.  The reservoir’s watershed drains 104,800 acres of western Baltimore County and eastern Carroll County (the majority of watershed is located in Carroll County).  A dam was completed on the North Branch Patapsco River in 1953, creating the Liberty Reservoir, which is owned by the City of Baltimore and managed by the Baltimore City Department of Public Works (BCDPW).  Water supply intakes in the reservoir feed the BCDPW’s Ashburton Water Filtration Plant, which provides drinking water to Baltimore City, Carroll County, and Baltimore County.  The reservoir is primarily fed by the North Branch Patapsco River; other tributaries include Beaver Run, Keyer’s Run, Prugh Run, Morgan Run, Middle Run, Locust Run, and Cooks Branch. 

Maryland’s water quality standards specify that all surface waters of the State shall be protected for water contact recreation, fishing, and the protection of aquatic life.  The specific Maryland Surface Water Use Designation in the Code of Maryland Regulations (COMAR) for Liberty Reservoir is Use I-P (Water Contact Recreation, Protection of Aquatic Life, and Public Water Supply). 

The Maryland Department of the Environment (MDE) has identified Liberty Reservoir on the State’s 2012 Integrated Report as impaired by mercury in fish tissue (2002), sediments – sedimentation/siltation (1996), nutrients – phosphorus (1996), and metals – chromium and lead (1996).  The non-tidal portion of the Liberty Reservoir watershed has been identified by MDE on the State’s 2012 Integrated Report as impaired by bacteria (mainstem only; 2002) and impacts to biological communities (2004).

A data solicitation for mercury was conducted by MDE and all readily available data up to the time of the WQA development have been considered.   A WQA for chromium and lead in Liberty Reservoir was approved by the EPA in 2003, and a fecal coliform TMDL for the nontidal portion of the watershed was approved by the EPA in 2009.  TMDLs for phosphorus and sediments were submitted to EPA in 2012 and approved in 2014.  In the final 2012 Integrated Report, the biological listing was addressed by the Biological Stressor Identification (BSID) analysis which more specifically identified chloride as a  stressor to biological communities within the 1st- through 4th-order streams of the Liberty Reservoir watershed.  As a result, in the 2012 Integrated Report, the biological impairment listing was replaced with a Category 5 chlorides listing.    

Water Quality Analysis of Mercury in Fish Tissue in Liberty Reservoir in Baltimore and Carroll Counties, Maryland 

(Approved on May 6, 2014)

EPA's Approval Letter EPA's Approval Letter
(Does not include MDE's requested revisions)
MDE's Edits to EPA's Approval Letter MDE's Approval Letter Edits
Main Report

Liberty_Reservoir_Mercury_WQA_final.pdf (1,700KB)

Comment Response Document

Liberty_Reservoir_Mercury_CRD_final.pdf (23KB)


Contact Information

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