Chloroform contamination in part of the alluvial aquifer, Southwest Louisville, Kentucky

A well in the Ohio River alluvium at Louisville, Ky., has been yielding water with chloroform concentrations as high as 34.80 milligrams per liter since July 1975. A spill of 5,000 gallons of chloroform in 1970, 120 feet from the well, is probably the source of the contamination. The chloroform is adsorbed in the unsaturated zone in the alluvium; the greatest concentrations are presently at and slightly above the water table. Lesser amounts of carbon tetrachloride are found with the chloroform. Its source is unknown.

The two contaminants were above the water table in the alluvium until a long-term trend of rising ground-water levels caused water to reach the contaminants and the water-chloroform mixture began moving downgradient to the well. High river stages cause a seasonal cycle of water-level rise, generally in late spring and midsummer; the ground water comes in contact with more chloroform and the chloroform concentration of the well water increases. No carbon tetrachloride has been observed in the well water.