Soil and groundwater beneath a region of a manufacturing plant are contaminated with automatic transmission fluid (ATF). The extent of contamination was assessed by maximizing the use of real-time data from soil-core sampling and monitoring wells. The number, location, and depth of cores and of monitoring wells were determined during the investigation based on: (1) inspection and analysis of soil-core samples immediately after each core was taken; (2) physical and chemical measurements of core samples at the end of each day; (3) measurements in monitoring wells at several stages during the investigation. This approach differs significantly from the conventional approach of randomly placing wells through the hydrogeologic system. Soil cores were taken and monitoring wells installed at 53 locations. The perched aquifer extends to about 13 ft. and is comprised mainly of sandy materials, which have spatial heterogeneity in size distribution and hydraulic properties. About 208 000 +/- 33 000 gal. of ATF has spread over an area of about 64 000 ft.2. The region of ATF contamination is comprised of three distinct and contiguous layers. The center layer is about 2.6 ft. deep at its thickest point and extends to about 250 ft. at its widest point. The soil in this zone is about 85% saturated with 133 000 +/- 21 000 gal. of ATF, which has depressed the water table into the aquifer. The top layer is about 14 in. thick and econtains about 50 640 gal. of ATF held by capillary forces. The amount of ATF in this zone decreases with height above the center layer from about 85% saturation to residual saturation (20%). The amount of ATF in the deepest layer is near the residual saturation. This layer is 1.0 +/- 0.5 ft. thick and has 24 500 +/- 12 250 gal. ATF. This investigative approach did not spread the ATF to clean regions of the aquifer as could occur with conventional approaches, and it provided the data needed to assess the problem and to design a cleanup plan. A new approach is being used to recover the free ATF at the site.
