Identification of E. coli

Project Title Identifying Sources of Fecal Coliform Bacteria in Selected Streams on Virginia's TMDL Priority List Number VA129 Location Selected Virginia river basins  Cooperating Agencies Virginia Department of Conservation and Recreation Virginia Department of Environmental Quality Fairfax County  Project Chief Ken Hyer Period of Project 1999 to present

Loading gels for DNA analysis

Problem
The Commonwealth of Virginia is required to develop Total Maximum Daily Loads (TMDLs) for stream segments that violate water quality standards for fecal coliform bacteria.  One of the major difficulties in establishing these TMDLs is the uncertainty inherent in identifying specific sources of fecal coliform bacteria in the streams.  Source tracking of fecal coliform  bacteria will provide more accurate waste-load allocations and will enhance the development and defensibility of TMDLs.

Objective
The objectives of this study are: (1) to test and determine the effectiveness of bacteria source tracking in identifying the sources of fecal contamination in three stream segments covering a range of agricultural and urban sources; (2) to evaluate and demonstrate the utility of source tracking to enhance model waste-load allocations, calibration, and verification.

Relevance and Benefits
In terms of projects of statewide importance, this project will demonstrate an innovative approach and provide needed  TMDL development support.  The project will benefit the Commonwealth by introducing a demonstrated state-of-the-art bacteria source-tracking technique to Virginia.  The project will also educate the public and state and federal policy makers on the range of fecal coliform bacteria contaminant sources in urban, agricultural, and mixed land-use watersheds that are on the Commonwealth's TMDL priority list.  Most importantly, this study will demonstrate the ability to improve watershed-modeling techniques, which will be widely applied over the next decade in the development of TMDLs for hundreds of stream segments in Virginia and other mid-Atlantic area states.  The significance of the proposed project is that it has the potential to provide improved bacterial source information in place of the "best guesses" that are currently being used for waste-load allocations, and thereby can strengthen the modeling results and the defensibility of the TMDLs.

Approach
Ribotyping, an analysis of the genetic material that codes for ribosomal RNA production of E. coli (originating in the digestive tract of warm-blooded animals), will be used to determine the dominant sources of fecal coliform in the impaired stream segments.  Samples will be collected over a range of hydrologic conditions from both the contaminated surface waters and all potential significant sources of fecal contamination.  The gene for ribosomal RNA production of E. coli isolates in the three surface water segments will be compared with isolates of defined sources within each watershed to determine major contributors to the fecal contamination.  The source-tracking distribution determined in each segment will be used to modify and strengthen the waste-load allocations in the TMDL watershed model.