A Waste Treatment/Disposal Site Evaluation Process for Areas Underlain by Carbonate Aquifers

Fractured carbonate or karst aquifers are highly susceptible to contamination. In Minnesota, the areas underlain by karst aquifers are often characterized by thin soil cover, poorly cased wells and/or collapse features. When coupled with improper land use decisions these aquifers have become extensively contaminated. Evaluation of existing or potentially contaminated sites has required development of unique site evaluation techniques or combinations of techniques. Shallow geophysics have been used successfully to determine subsurface karst features, pinpoint locations for additional investigations and evaluate pump‐test data. Soil texture, density and relative moisture content have been closely examined and criteria established to evaluate subsurface erosion susceptibility. Percent rock core recovery, mechanical response of drilling and drilling fluid loss have been used to characterize the secondary porosity and potential contamination susceptibility of the carbonate rock. Dye tracing via surface sinks and well injection have determined primary flow paths and have been useful in estimating flow times. These techniques used solely or in conjunction have been very useful in evaluating contamination existing in the aquifers and as a predictive tool to evaluate the proposed land uses impacts.