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Four Mile Run TMDL Implementation
Total Maximum Daily Load (TMDL)
TMDL, allocation studies, and subsequent Implementation Plans (IPs) go hand-in-hand with water quality standards.

About TMDL
1972 - Congress enacts the Federal Water Pollution Control Act, commonly known as the Clean Water Act (CWA)
  • Required states to develop water quality criteria
  • Required states to monitor waterbodies within their boundaries for compliance
  • Required states to report non-compliant waterbodies to the US Environmental Protection Agency (USEPA)
  • 303(d) Impaired Waters List cites the specific portion of the waterbody and specific unmet water critieria
There was a significant delay from 1972 prior to states actually developoing 303(d) Impaired Water Lists - the first list was produced in 1994. Virginia produced its first list in 1996. Impaired water lists are prepared by the states for the USEPA biennially on even-numbered years.

TMDL Allocation Study
Once listed as impaired, the CWA requires states to develop a TMDL allocation study:
  • Specific to the particular water segment of interest 
  • Specific to the impairment
  • Multiple impairments in the same water segment may require multiple TMDL allocation studies
Allocation studies limit the pollutant loads allowable from each pollutant contributor in the watershed to levels that will ensure that the water quality standard is achieved.

Implementation Plans (IPs)
Implementation Plans are:
  • Not explicitly required by the CWA
  • A management strategy that takes the load allocations developed and forms corrective actions to be taken to bring the water segment into compliance
Beginning in 1997, Virginia requires IPs be developed for every TMDL developed in the state.

Four Mile Run's TMDL History
  • 1996 - 303(d) Impaired Waters List for failing to meet water quality standards for fecal coliform bacteria.
  • 1998 - Subsequently listed, bringing it under a 1999 consent decree requiring Virginia to develop TMDL's by 2010 for all water segments listed on the 1998 Virginia 303(d) Impaired Waters List.
  • 2002 - Completion of the TMDL for the non-tidal portion of Four Mile Run. Marked the first urban nonpoint source TMDL for Virginia and one of the first in the country. The fecal coliform impairment in the tidal portion of Four Mile Run is yet to be addressed. It must be developed by 2010.
  • 2002 - Virginia 303(d) Impaired Waters List cited Four Mile Run additionally for PCB contamination in fish tisue. Development of a TMDL to address this has not yet been scheduled.
  • Read Four Mile Run's TMDL Plan

TMDL Links and Contact Information
The NVRC Staff Contact for TMDL efforts in the Four Mile Run is Sayedul Choudhury or 703-642-4633

Northern Virginia Regional Commission • 3060 Williams Drive, Suite 510 • Fairfax, VA 22031 • 703-642-0700 (Voice) • 703-642-5077 (FAX) • Email Us