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USING DIRECT-PUSH TOOLS TO MAP HYDROSTRATIGRAPHY AND PREDICT MTBE PLUME DIVING
Citation:
Wilson*, J T., R. Ross, AND S Acree*. USING DIRECT-PUSH TOOLS TO MAP HYDROSTRATIGRAPHY AND PREDICT MTBE PLUME DIVING. SUMMER 2005, GROUNDWATER MONITORING AND REMEDIATION. National Ground Water Association, Westerville, OH, 25(3):93-102, (2005).
Impact/Purpose:
Journal Article
Description:
Conventional wells for monitoring MTBE contamination at underground storage tank sites are screened a few feet above and a few feet below the water table. At some sites, a plume of contamination in ground water may dive below the screen of conventional monitoring wells and escape detection. If the aquifer that supplies a municipal well is at risk, the state regulatory agencies will often characterize the aquifer in three dimensions. The state agencies need tools and techniques to predict the vertical extent of MTBE contamination in an aquifer. Two techniques that are emerging in the site characterization market are electrical conductivity logging and pneumatic slug testing done in temporary push wells. These techniques were evaluated at a diving plume of MTBE in the aquifer that supplies water to the village of East Alton, Illinois. The plume stayed near the water table in the first 300 feet from the potential sources, then dived below conventional monitoring in the next 300 feet. At the location where the MTBE dived, the depth to water was 28 feet below land surface. The first thirty feet of material in the saturated zone had an electrical conductivity near 100 mSm, indicating silts and clays. An electrical conductivity near 25 mSm, which indicates sands or gravels, was encountered at a depth of 35 feet below the water table, and the sands and gravel extended to a depth of at least 50 feet below the water table. Pneumatic slugs tests measured low hydraulic conductivity in the interval of silt and clay (1.1 and 0.04 feet per day), and higher hydraulic conductivity in the interval with sands and gravels (41, 38 and 37 feet per day). Ground water with the highest concentration of MTBE was produced from the contact between the silt and clay and the sands and gravel.
URLs/Downloads:
Using Direct-Push Tools to Map Hydrostratigraphy, etc.
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