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Fecal-coliform bacteria concentrations in streams of the Chattahoochee River National Recreation Area, Metropolitan Atlanta, Georgia, May–October 1994 and 1995

This report is available online in pdf format (1.0 MB): USGS WRIR 00-4139 ()

M. Brian Gregory and Elizabeth A. Frick

U.S. Geological Survey Water-Resources Investigations Report 00-4139, 8 pages (Published August 2000)

Introduction

The Metropolitan Atlanta area has been undergoing a period of rapid growth and development. The population in the 10-county metropolitan area almost doubled from about 1.5 million people in 1970 to 2.9 million people in 1995 (Atlanta Regional Commission, written commun., 2000). Residential, commercial, and other urban land uses more than tripled during the same period (Frick and others, 1998). The Chattahoochee River is the most utilized water resource in Georgia. The rapid growth of Metropolitan Atlanta and its location downstream of the headwaters of the drainage basin make the Chattahoochee River a vital resource for drinking-water supplies, recreational opportunities, and wastewater assimilation. In 1978, the U.S. Congress declared the natural, scenic, recreation, and other values of 48 miles of the Chattahoochee River from Buford Dam to Peachtree Creek to be of special national significance. To preserve this reach of the Chattahoochee River, the U.S. Congress created the Chattahoochee River National Recreational Area (CRNRA), which includes the Chattahoochee River downstream from Buford Dam to the mouth of Peachtree Creek and a series of park areas adjacent to the river in northern Metropolitan Atlanta

Even with this protection, waters of the Chattahoochee River and many of its tributaries in Metropolitan Atlanta did not meet water-quality standards set for designated uses during 1994 and 1995 (fig. 1 and table 1). Much of the degradation of water quality has been associated with areas undergoing rapid urban growth and sprawling suburban development. The resulting conversion of mostly forested land to urban land has multiple adverse effects on water quality. Degradation of water quality may be caused by a number of factors including an increase in nutrient concentrations, sediment and sedimentbound contaminant concentrations (e.g., metals and pesticides) (Frick and others, 1998), and fecal-coliform bacteria concentrations (Center for Watershed Protection, 1999). The presence of fecal-coliform bacteria in streams and rivers indicates that contamination by fecal material from human or animal sources has occurred and contact with these waters can result in exposure to pathogenic bacteria often associated with fecal contamination.

During 1994 and 1995, elevated concentrations of fecal-coliform bacteria were the most common reason that the Chattahoochee River and tributaries did not meet their designated uses of drinking-water supply, recreation, and fishing. According to the Georgia Department of Natural Resources (1997), during 1994 and 1995, 67 of 77 stream reaches assessed in Metropolitan Atlanta did not meet or only partially met water-quality requirements for designated uses. Excessive concentrations of fecal-coliform bacteria were a contributing factor in 63 of the 67 streams that did not meet or only partially met designated uses. High concentrations of fecal-coliform bacteria have the potential to reduce the recreational value of the river and pose a continued threat, with unknown health risks, to humans that come in contact with the water while fishing, boating, rafting, wading, and swimming.

Significant Findings

• Fecal-coliform bacteria concentrations in the Chattahoochee River were low downstream from Buford Dam, especially nearest the dam, because of dilution from water released from near the bottom of Lake Sidney Lanier.
• Median fecal-coliform bacteria concentrations in the Chattahoochee River increased steadily from less than 20 Most Probable Number of colonies per 100 milliliters (MPN col/100 mL) in the tailwaters of Buford Dam on Lake Sidney Lanier to 790 MPN col/100 mL downstream of Metropolitan Atlanta. During the 1994 and 1995 summer recreation seasons, from 1 to 65 percent of samples collected at 14 Chattahoochee River monitoring sites exceeded the U.S. Environmental Protection Agency (USEPA) review criterion of 400 col/100 mL.
• Georgia Environmental Protection Division standards and the USEPA review criterion for fecal coliform bacteria were commonly exceeded during wet-weather conditions in most Metropolitan Atlanta tributary streams and during most streamflow conditions in several tributaries that drain areas dominated by urban and suburban land uses. During the 1994 and 1995 summer recreational season, from 27 to 100 percent of samples collected at 22 tributary stream-monitoring sites exceeded the USEPA review criterion of 400 col/100 mL.
• Statistically significant positive correlations were found between high fecal-coliform bacteria concentrations and increased discharges and high turbidities in less-developed tributary watersheds dominated by nonpoint sources such as runoff from parking lots, lawns, and pastures.
• In some highly urbanized tributary watersheds, there was an inverse correlation between high fecalcoliform bacteria concentrations and increased discharges and high turbidities, which indicates possible contamination from point sources such as leaking or overflowing sewer lines or discharge from combined sewer overflows.

CONTENTS

Introduction

Project Description

Distribution of Fecal-Coliform Bacteria

Sources of Fecal-Coliform Bacteria

Current Research

References

REPORT AVAILABILITY

This report is available online in pdf format (1.0 MB): USGS WRIR 00-4139 ()
To view the PDF document, you need the Adobe Acrobat® Reader installed on your computer. (A free copy of the Acrobat® Reader may be downloaded from Adobe Systems Incorporated.)

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