Investigation of Failure Mechanisms and Migration of Organic Chemicals at Wilsonville, Illinois

Abstract

Ground water contamination was discovered in 1981 in a monitoring well at the Earthline disposal facility near Wilsonville, Illinois. Organic chemicals had migrated at a rate 100 to 1000 times greater than predicted when the site received its permit to operate in 1978. Postulated failure mechanisms included migration through previously unmapped permeable zones, subsidence of an underground mine, organic‐chemical and clay‐mineral interactions, acid‐mine drainage and clay interactions, trench‐cover settlement, and erosion. In this investigation, the Illinois State Geological Survey found the primary reason for the rapid migration: the presence of previously undetermined fractures and joints in glacial till. The inaccurate predictions of hydraulic conductivity were based on laboratory‐determined values that did not adequately measure the effects of fractures and joints on the transit time calculations. Field‐measured hydraulic conductivity values were generally 10 to 1000 times greater than their laboratory‐measured counterparts, thus largely accounting for the discrepancy between predicted and actual migration rates in the transit time calculations. The problem was compounded, however, by the burial of liquid wastes and by trench covers that allowed excess surface runoff to enter the trenches. Organic‐chemical and clay‐mineral interactions may also have exacerbated the problem in areas where liquid organic wastes were buried.

Contaminant impact assessment and the contaminating lifespan of landfills

“…However, conventional hydrogeologic investigations of "unweathered" soils have typically implied that they are unfractured. Recent research and field investigations, which have included angled boreholes or deep test pits in clayey tills, suggest that conventional investigations may be misleading and that many of these unweathered soils are indeed fractured to depths of as much as 10 m (e.g., Herzog and Morse 1986;Ruland 1988;D7Astous et al 1989;Herzog et al 1989;McKay, personal communication). Typically, the fracture frequency decreases with depth and, in most cases examined by the author, the fractures could be observed terminating at some depth within the test pit.…”

A multiscale study of the permeability of a thick clayey till

“…Uses of this approach [e.g., Grisak and Cherry, 1975; Rodrigues, 1983; Keller et al, 1986] have been limited to relatively small thicknesses and/or units with relatively high permeabilities. Lacking fortuitous circumstances or settings, many investigators have obtained K values from laboratory tests [e.g., Law and Lee, 1981; Tavenas et al, 1983b] and/or singlepiezometer response ("slug") tests [e.g., Williams and Far volden, 1967;Schwartz, 1975;Prudic, 1982;Hendry, 1982;Cravens and Ruedisili, 1987;Hendry, 1988;Herzog et al, 1989] in hopes that these values represent the bulk value. As has been recognized by many of these workers, this extrapolation is fundamentally weak to the extent that the following questions have not been answered:1.…”

Slug Test Analysis to Evaluate Permeability of Compressible Materials

“…The geology of the target site in Wilsonville, Illinois, consists primarily of fine‐grained glacial till called Vandalia Till. Laboratory falling head tests were conducted on remolded soil samples from the site to evaluate hydraulic conductivity which ranged from 1.2 × 10 −8 to 7.4 × 10 −8 cm/s for the weathered till and 1.3 × 10 −8 to 2.7 × 10 −8 cm/s for the unweathered till (Herzog et al 1989).…”