Dissolved constituents in seepage from fly-ash settling ponds bordering part of the Indiana Dunes National Lakeshore (the Lakeshore) have increased the concentrations of major ions (calcium, fluoride, potassium, and sulfate), trace elements (aluminum, arsenic, boron, iron, manganese, molybdenum, nickel, strontium, and zinc), and gross alpha and beta radioactivity in ground water and surface water downgradient from the settling ponds. Data collected from September 1976 through May 1978 suggest that concentrations of some dissolved trace elements may be greater beneath interdunal pond 2 than in the pond. The soil system downgradient from the settling ponds seems to have affected the concentrations of dissolved ions in the settling-pond seepage. Calcium concentrations were greater in ground water downgradient from the settling ponds than in the ponds. Where organic material was present downgradient from the settling ponds, concentrations of arsenic, fluoride, molybdenum, potassium, sulfate, and strontium were greater in the ground water than in the ponds. In contrast, the concentrations of cadmium, copper, nickel, aluminum, cobalt, lead, and zinc were less.
Leachate from an ash fill bordering the Lakeshore increased concentrations of boron, molybdenum, and potassium in surface water.
Although concentrations of chemical constituents were variable, data indicate that ground-water in a confined aquifer beneath the study area was not significantly affected by settling-pond seepage.
