Stream Protection Strategy Other Initiatives


Accotink Creek Bacteria Source Tracking in Partnership with the U.S. Geological Survey

Map of Accotink CreekIn 1998, a 4.5 mile segment of Accotink Creek in Fairfax County, beginning at the confluence of Crook Branch and Accotink Creek to the start of Lake Accotink, was placed on the Virginia 303(d) Total Maximum Daily Load priority list for fecal coliform impairment. As a result of this, the Fairfax County Health Department entered into a partnership with the U.S. Geological Survey, the Virginia Department of Conservation and Recreation, and Virginia Department of Environmental Quality to pursue a bacteria source tracking study for Accotink Creek as part of a statewide study. The initial study results indicated that the sources of bacteria are distributed as: 40 percent waterfowl, 20 percent human, 13 percent dogs, 5.4 percent raccoon, 1.4 percent deer, and 21 percent other.

Based on the results of this initial study, the Department of Environmental Quality published a draft Total Maximum Daily Load that includes a goal to reduce the human sources of fecal coliform bacteria by 99 percent. In response to this draft Total Maximum Daily Load, the U.S. Geological Survey initiated another study in cooperation with Fairfax County Stormwater Planning Division, City Exposed Sanitary Sewer Lineof Fairfax, and the Department of Conservation and Recreation to help identify the distribution of fecal coliform and locate specific sources of human fecal coliform inputs to Accotink Creek. This second study began in December 2001 and continued through December 2003 with Stream Protection Strategy staff assisting with the field sampling and analysis efforts.

The data compiled from this study will help provide a better understanding of the transport mechanisms and sources of the human wastewater signal in Accotink Creek. Ultimately, this study will support a cost-effective implementation plan for the more than 175 stream segments in Virginia which violate the water quality standard for fecal coliform bacteria.

Additional information is available from the U.S. Geological Survey.

Perennial Stream Identification and Mapping Project

Perennial Stream Field SurveyPerennial streams flow all year except in extreme hydrologic droughts. These streams have certain water (hydrological), channel (geomorphological) and life (biological) characteristics which make them unique. Under the Fairfax County Chesapeake Bay Preservation Ordinance, streams with perennial flow receive protection by a Resource Protection Area, a buffer of at least 100 feet limiting the amount of development occurring adjacent to a stream.

In 1992, the Fairfax County Board of Supervisors adopted the original Chesapeake Bay Preservation Ordinance defining perennial streams as those depicted as solid blue lines on U.S. Geological Survey maps. Unfortunately, these maps are known to have errors in accurately determining the true upper extent of perenniality. In recognizing this problem, the Fairfax County Environmental Quality Advisory Council made a recommendation to the Board of Supervisors that the streams be field-verified to complete the county's stream maps used for regulatory purposes. The Fairfax County Stormwater Planning Division took on this task.

The Perennial Streams Identification and Mapping project began with the development of a protocol to identify the breaking point between perennial streams and intermittent streams, which will dry up during dryer months. Mirroring a protocol for identifying the boundary between streams that flow only after storm events (ephemeral streams) and intermittent streams developed by the North Carolina Department of Environment and Natural Resources, the Fairfax County Perennial Stream Identification Protocol was created, with changes made for regional differences. A pilot study was conducted in the fall of 2001 comparing results from locations in three Fairfax County watersheds with varying degrees of development and underlying geology. Field work began in March 2002 and was completed in October 2003.

The new Chesapeake Bay Preservation Area Maps, including the newly designated perennial streams and the corresponding Resource Protection Areas, were adopted by the Board of Supervisors in November 2003. This was a major step forward towards improving the water quality of both the county's streams and those downstream in neighboring jurisdictions.


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