Microbial Contamination of Water Resources in the
Chattahoochee National Recreation Area, Georgia

ABSTRACTS

Gregory, M.B., and Frick, E.A., 2000, Fecal-coliform concentrations in streams in the Chattahoochee River National Recreation Area and surrounding areas, Georgia, May-October 1994 and 1995 [abs.]: in Building Capabilities for monitoring and assessment in public health microbiology, Columbus, Ohio, March 2000, unpaginated. The Chattahoochee River is the principal drinking-water source in Metropolitan Atlanta and water-based recreation constitutes 25-30 percent of the 3.5 million yearly visits to the Chattahoochee River National Recreation Area (CRNRA). The CRNRA includes 48 miles of the Chattahoochee River downstream from Buford Dam to the mouth of Peachtree Creek and 14 park units adjacent to the river in northern Metropolitan Atlanta. Within the Metropolitan Atlanta area, elevated fecal-coliform concentrations are the principal reason for streams not supporting or only partially supporting designated uses. Although, elevated concentrations of fecal-coliform bacteria do not necessarily pose a risk of illness, concentrations of these bacteria have traditionally been used to indicate that fecal contamination of the water has occurred, as well as the potential presence of pathogens. In 1998, the U.S. Geological Survey (USGS) in cooperation with the National Park Service (NPS) began a study to evaluate the extent of microbial contamination in the CRNRA. As part of this study, the USGS retrospectively analyzed fecal-coliform data collected by the Georgia Environmental Protection Division (GaEPD) in the Chattahoochee River basin during the 1994 and 1995 summer recreation seasons. Fecal-coliform concentrations in many streams in the study area frequently exceeded GaEPD instream standards (based on the geometric mean of at least 4 samples collected within 30 days) and commonly exceeded maximum concentrations recommended for the designated uses of drinking water, recreation, and fishing. When four fecal-coliform samples are not collected at least 24-hours apart and within 30 days of one another, the U.S. Environmental Protection Agency (USEPA) recommends using a review criterion of 400 colonies per 100 milliliters (colonies/100 mL) rather than geometric-mean-based State standards. Fecal-coliform concentrations exceeded the USEPA review criteria in 1 to 89 percent of samples collected from 14 Chattahoochee River monitoring sites and in 42 to 100 percent of samples collected from 22 tributary monitoring sites. During the 1994-95 summer recreation seasons, tributary streams having the lowest median fecal-coliform concentrations drained the least developed areas, generally upstream and downstream from Metropolitan Atlanta. Tributary streams having the highest median fecal-coliform concentrations drained densely developed urban and suburban areas. Fecal-coliform concentrations in streams increased during storm runoff in response to nonpoint-source contributions. High concentrations of fecal coliforms detected in a few urban streams during baseflow suggest that these tributaries may be affected by point-source contamination, such as leaking or overflowing sanitary sewers. In the 67-river-mile reach of the Chattahoochee River downstream from Buford Dam, median fecal-coliform concentrations increased from less than 20 colonies/100 mL to 790 colonies/100 mL downstream of Metropolitan Atlanta. The GaEPD data set is the most extensive data set available on fecal contamination in Metropolitan Atlanta and retrospective analysis of these data provides the NPS a summary of the magnitude and scope of microbial contamination in the vicinity of its park units. By including these historical data from within and downstream of the CRNRA, spatial, temporal, and land-use coverages beyond the scope of the current USGS and NPS project were available to augment project design. These data indicate widespread and persistent exceedences of GaEPD standards and USEPA review criteria in Metropolitan Atlanta during the 1994-95 summer recreation seasons. Widespread exceedences further emphasize the need for improved methods for the identification of major sources and transport pathways of microbial contamination to aid in design of abatement programs. Authors: 1 Physical Scientist, U.S. Geological Survey, Atlanta, Georgia (706-369-7739; alfunk@usgs.gov) ; 2 Ecologist, U.S. Geological Survey, Atlanta, Georgia (770-903-9163; bgregory@usgs.gov )

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