Streamflow, water-quality, and biological conditions in the Big Black Creek basin, St. Clair County, Alabama, 1997
In 1997 synoptic streamflow, water-quality, and biological investi- gations in the Big Black Creek Basin were conducted by the U.S. Geological Survey in cooperation with the City of Moody, St. Clair County, and the Birmingham Water Works Board. Data obtained during these synoptic investigations provide a one-time look at the streamflow and water-quality conditions in the Big Black Creek Basin during a stable, base-flow period when streamflow originated only from ground-water discharge. These data were used to assess the degree of water-quality degradation in the Big Black Creek Basin from land-use activities in the basin, including leakage of leachate from the Acmar Regional Land- fill. Biological data from the benthic invertebrate community investigation provided an assessment of the cumulative effects of stream conditions on organisms in the basin. The synoptic measurement of streamflow at 28 sites was made during a period of baseflow on August 27, 1997. Two stream reaches above the landfill lost water to the ground-water system, but those below the landfill had significantly higher ground-water gains. If significant leakage of leachate from the landfill had occurred during the measurement period, the distribution of ground-water discharge suggests that leachate would travel relatively short distances before resurfacing as ground-water discharge to the stream. Benthic invertebrate communities were sampled at four sites in the Big Black Creek Basin during July 16-17, 1997. Based on Alabama Department of Environmental Management criteria and on comparison with a nearby unimparied reference site, the benthic invertebrate communities at the sites sampled were considered unimpaired or only slightly impaired during the sample period. This would imply that landfill and coal-mining activities did not have a detrimental effect on the benthic invertebrate communities at the time of the study. Synoptic water-column samples were collected at nine sites on Big Black Creek and its tributaries at the same time that the synoptic streamflow measurements were made. Trace-element and organic compound concentrations in the stream water were below established water-quality standards and criteria for the State of Alabama, with the exception of secondary (aesthetic) drinking-water levels for iron and manganese. Oil and grease concentrations detected in bed sediments were below the corrective action limit of 100 milligrams per kilogram. No significant increases in chloride, specific conductance, total dissolved solids, oil and grease, color, or biochemical oxygen demand were observed at sites downgradient from the landfill. Ground-water samples were collected from three drive-point wells in the vicinity of the landfill. These samples were analyzed for a suite of volatile organic compounds. The solvent 1,1-dichloroethane (the same solvent detected in the ground-water monitoring system at the landfill) was detected in a sample from a drive-point well downgradient from the landfill--an indication of the potential risk of landfill-derived contamination migrating toward Big Black Creek. No distinguishing trend or pattern of contamination was identified that could be attributed solely to landfill activities. Landfill activities did not appear to contribute significant contamination to Big Black Creek during these streamflow conditions. Any contaminant contribution from coal-mining activities in the basin may have served to mask any leachate contributions from the landfill; however, the overall effects on stream water and benthic intervebrate communities apparently were only minimal.