This study was undertaken to develop modifications for improving cost and time efficiencies without sacrificing accuracy and precision to the current method employed by the Indiana Department of Transportation (INDOT) for determining sulfate content in soils. In addition, GIS maps of Indiana were prepared for displaying the distribution of sulfate concentration in soils and shallow groundwater to provide guidance where high sulfate areas might exist and to show where gaps occur in available data.

The IGS study confirmed that the current INDOT test method using 1:20 soil/water ratio and turbidimetric method for analyzing sulfate are optimal. A conductivity screening test on soil leachate eliminated the need to run a turbidity sulfate test for most samples, reducing the time necessary for filtering, and the cost of materials for running the test. Of the 11 samples in this study, 73% had conductivity readings corresponding to

Contour maps of the distribution of sulfate in soils and groundwater were prepared with data from multiple agencies. Gaps in the data sets limit the usefulness of the current maps. In places of good data density, areas of minimal sulfate are distinguished from areas with elevated sulfate content, indicating how a more completed data set would be valuable as a guide to problem areas throughout the state. Some areas of elevated groundwater sulfate coincided with elevated soil sulfate, suggesting a correlation. However, the areal distribution gaps in both data sets prevent a more definitive interpretation.

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sulfate test methods, conductivity screening, soil sulfate, groundwater sulfate, Indiana maps

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version