Engineering geology investigations of a hazardous-waste landfill in West Central Illinois,USA

Faster-than-predicted pollutant migration at a state-licensed, hazardous-waste landfill was investigated 3 years after its operation was ceased by court order. At that time, the operator of the landfill discovered organic chemicals in a monitoring well during routine sampling, suggesting laekage from the trenches at a rate of 100 to 1000 times faster than predicted by the laboratory tests made for the initial landfill design. To determine the causes for this rapid pollutant migration, investigators studied site geology and stratigraphy, mine subsidence, hydrogeology, condition of waste containers, trench covers, and soil properties. Organic chemical probably leaked when meteoric waters drained freely through the trench covers, flushing liquid wastes from the burial trenches into the permeable, fracture ablation till. Interpretation of aerial photographs was used to find depressions and surface impediments in covers through which the drainage occurred. Pipe-type depressions in covers were probably caused by highly erodible (dispersive) soils. Surface impediments, such as roads and erosion-control dikes, caused runoff to pool over the trench covers. In an attempt to eliminate these problems, the following studies are proposed: geologic studies in exploration and design, field hydrogeologic tests, laboratory tests for highly erodible soils, and postclosure monitoring by photointerpretation and remote sensing.