Water Quality Analyses (WQA) with EPA Concurrence of MDE's Findings: Middle Patuxent River

The Middle Patuxent River watershed is located in the center of Howard County. Its headwaters are in the northern portion of the county, originating primarily in agricultural areas. The river flows through various farms and subdivisions, and the more southern portions (below MD-Route 108) are near the Columbia business center, in the Planned Service Area. The main transportation corridors in the watershed are Interstate-70 across the northern section, Interstate-95, and MD-Routes 29 in the southern portion, and 32, which runs the length of the watershed.  The drainage area of Middle Patuxent River watershed is 37,052 acres. 

Middle Patuxent River (basin code 02131106, non-tidal watershed) was identified on the State’s list of  WQLSs as impaired by nutrients (1996), sediments (1996), metals-zinc (1996) and impacts to biological communities (2002).  This document upon EPA approval, addresses the nutrient impairment in Middle Patuxent River; the listings for sediment, metals-zinc, and impact to biological communities will be addressed at a future date. The metals listing will be addressed in 2006.

An analysis of recent monitoring data shows that the dissolved oxygen criterion and designated uses associated with nutrients are being met in Middle Patuxent River.  The analysis supports the conclusion that a TMDL for nutrients is not necessary to achieve water quality standards in this case.  Barring the receipt of contradictory data, the report available below will be used to support a nutrients listing change for the Middle Patuxent River from Category 5 “waterbodies impaired by one or more pollutants requiring a TMDL” to Category 2 “Surface waters that are meeting some standards and have insufficient information to determine attainment of other standards”, when the Maryland Department of the Environment (MDE) proposes the revision of Maryland’s 303(d) List for public review in the future.

Although the waters of Middle Patuxent River do not display signs of eutrophication, the State reserves the right to require future controls in the Middle Patuxent River watershed if evidence suggests nutrients from the basin are contributing to downstream water quality problems.     

Water Quality Analysis of Eutrophication for the Middle Patuxent River, Howard County, Maryland

(Concurrence February 21, 2007)

EPA's Decision Letter EPA's Decision Letter

Main Report 

WQA_Middle_Pax_River_eutro.pdf (586KB)

Comment Response Document

CRD_Middle_Pax_river_eutro.pdf (103KB)

Contact Information

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