A study was performed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to describe the geohydrology and distribution of light-nonaqueousphase liquids in an industrialized area of northwestern Indiana and northeastern Illinois. The geologic units of concern underlying this area are the carbonates of the Niagaran Series, the Detroit River and Traverse Formations; the Antrim Shale; and sands, silts, and clays of Quaternary age. The hydrologic units of concern are surface water, the Calumet aquifer, the confining unit, and the Silurian-Devonian aquifer.
Water levels collected in June 1992 indicate that the water-table configuration generally is a subdued reflection of topography. Recharge from landfill leachate and ponded water, discharge to sewers, and pumping also affect the water-table configuration. A depression in the potentiometric surface of the Silurian-Devonian aquifer results from pumping. Light-nonaqueous-phase liquids were detected near petroleum handling, industrial and waste-disposal facilities.
Horizontal ground-water velocity at the water table in the confining unit ranged from 4.4x10-4 to 1.0x10-3 feet per day. Horizontal ground-water velocity in the Calumet and Silurian-Devonian aquifers ranged from 1.0x10-2 to 3.4x10-1 and from 1.4x10-2 to 2.9x10-2 feet per day, respectively.
Vertical hydraulic gradients indicate generally downward flow from the Calumet aquifer into the confining unit, then into the Silurian-Devonian aquifer. Calculated vertical groundwater velocity through the weathered and unweathered parts of the confining unit are 3.8x10-2 and 1.5x10-3 feet per day, respectively.
