Loudoun Soil and Water Conservation District
TMDL (Total Maximum Daily Load)
Stream Monitoring Program

Red lines delineate segments of streams considered impaired according to the VA Department of Environmental Quality 1998 303(D) Total Maximum Daily Load Priority List and Report

WHAT IS TMDL?

What does TMDL Mean to Loudoun County?

Total Maximum Daily Load (TMDL) is the specific pollutant that a water body can receive and still maintain water quality standards. Section 303(d) of the 1972 Clean Water Act enhanced the TMDL process for identifying and restoring the quality of impaired waters.

In Virginia, TMDL is a three-step process: the first step identifies impairment sources and calculates the daily load; the second step is the development of an implementation plan that addresses allocation of allowable pollutant loads so the water body will meet the water quality standard, and the third step is implementation of the plan.

Loudoun County's water quality is impacted by nine stream segments listed on Virginia's 1998 303(d) list as exceeding acceptable levels of fecal coliform and one stream segment with benthic (aquatic life) impairment. Fecal contamination of water bodies is from point and nonpoint source contributions. Nonpoint sources of fecal contamination include human, livestock, and wildlife. DEQ lists 3 segments in the Catoctin Creek watershed exceeding fecal coliform water quality standards; one segment in the Goose Creek watershed for benthic life impairment and 5 segments for fecal coliform; and in Piney Run watershed, DEQ lists one segment for fecal coliform impairment. The TMDL development for impaired segments in Loudoun County is scheduled to be completed by May 2004.

In Virginia, the Departments of Environmental Quality (DEQ) and Conservation and Recreation (DCR) are the lead agencies working in partnership with EPA, local and state governments, private consultants and local stakeholders to develop all listed TMDLs.