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Field verification of ground water pollution potential in fractured environments using modified DRASTIC methodology

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  072143.(doi:10.13031/2013.22938)
Authors:   Ann D Christy, Julie Weatherington-Rice, Michael Angle, Linda Aller
Keywords:   preferential flow, ground water vulnerability, pollution potential mapping, fractured glacial till

The ground water vulnerability assessment model, DRASTIC, was modified in 1995 to better evaluate the effect of fractured till. Published in 1987, the original DRASTIC methodology used seven parameters to assess ground-water pollution potential. The seven parameters form the acronym DRASTIC: “D” Depth to water, “R” Net Recharge, “A” Aquifer media, “S” Soil media, “T” Topography, “I” Impact of the vadose zone media, and “C” hydraulic Conductivity. Over time, it became clear that DRASTIC needed to be modified to incorporate the preferential flow effects of fractured glacial till. Several DRASTIC parameters were modified to better reflect the fractured nature of underlying parent materials including Net Recharge (R), Impact of the vadose zone media (I), and Soil media (S). Ohio researchers decided to field-verify these modifications. Twenty-one field sites within the glaciated portion of Ohio were studied to determine if fractures were present in the soils and the underlying parent materials. All 21 sites were evaluated for their existing DRASTIC settings and, where necessary, new Ground Water Pollution Potential numbers were assigned. In 2000, Ohio soil scientists had identified 95 soils found in Ohio to be fractured in the C horizon. The DRASTIC field research project confirmed 23 of these 95 soils, and added four new soils to the list: Amanda, Avonburg, Blanchester, and Clermont. Modification of the DRASTIC mapping methodology makes this ground water pollution potential mapping system even more accurate and protective of water supplies especially in preferential flow environments. DRASTIC mapping can play an important role in regional and local ground water pollution protection efforts.

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