TMDL Development

Impaired Waters by County (August 2008): This is a Microsoft Excel spreadsheet listing all impaired waters in the Rappahannock-Rapidan region by county, year and impairment type.

What is a TMDL?
A TMDL, or Total Maximum Daily Load, is a term used to describe the amount of pollution a stream can receive and still meet Water Quality Standards. Water Quality Standards are regulations based on federal or state law that set numeric or narrative limits on pollutants. TMDLs are required for waterbodies that have been determined to be impaired. The Virginia TMDL program is governed by a federal court order Consent Decree which lays out a schedule for TMDL Development through 2010.

What is the purpose of a TMDL Study?
A TMDL study identifies sources of pollution and reductions needed to attain water quality standards. A TMDL considers point sources such as residential, municipal, or Industrial discharges and non-point sources such as residential, urban, or agricultural runoff. Virginia’s goal is that all streams attain the applicable beneficial use(s) for which they have been designated, e.g., drinking water, swimming, fishing, shell-fishing, and aquatic life use. These are protected by application of the state’s water quality standards.

How does Virginia determine what is an Impaired Water?
Through water quality monitoring and assessment (i.e., comparing the monitoring data to the applicable water quality standards), the Virginia Department of Environmental Quality (DEQ) determines whether a waterbody is impaired or not. Every even numbered year, Virginia submits a list of the waters found to be impaired, referred to as the 303(d) list, to the Environmental Protection Agency. Currently, 636 waters have been determined to be impaired across the state.

- from Frequently Asked Questions About. . . TMDL Development, Virginia Department of Environmental Quality, March 2002, by J. Schneider.

Additional information on TMDLs can be found on the DEQ website located at:

TMDL Information from Virginia DEQ