Procedure for Determining Near-Surface Pollution Sensitivity

This procedure document outlines modifications to the DNR's Near-Surface Pollution Sensitivity mapping approach and provides supporting documentation for the transmission rates that will be used in future mapping of Near-Surface Pollution Sensitivity. It incorporates a systematic approach for determining infiltration developed by the Minnesota Geological Survey (MGS) for the Scott County Geologic Atlas update (Tipping, 2006) that was based on previous work completed by Barr Engineering (Barr, 2005). Barr's approach used estimated transmission rates to evaluate the near-surface time of travel to interpret infiltration for resource management. The estimated transmission rates for the near surface materials were taken from a Natural Resources Conservation Service (NRCS) online publication that estimated unsaturated hydraulic conductivities of soil hydrologic groups A, B, C, and D. Unfortunately, the NRCS documentation for the infiltration rates used in 2006 investigation is no longer available. DNR staff have adapted the approach for determining near surface pollution sensitivity for the Todd County Part B Geologic Atlas (Petersen, 2010), the Carlton County Part B Geologic Atlas (Berg, 2011), and the Benton County Part B Geologic Atlas (Rivord, 2012).