INVESTIGATING ROAD SALT CONTAMINATION USING GEOPHYSICS AND GEOCHEMISTRY

We investigated groundwater contamination in domestic wells located near a former New York State Department of Transportation road salt reloading facility near Vernon Center, New York. Eleven of the sixteen domestic wells have chloride concentrations greater than the EPA secondary drinking water standard of 250 mg/l and several wells have chloride concentrations that exceed 2000 mg/l. We used an electromagnetic induction (EM) tool to map the electrical conductivity of the shallow subsurface in the area. In addition, we analyzed water samples from domestic wells, ten monitoring wells associated with the reloading facility, and four mini-piezometers installed into the bed of a nearby creek using ion chromatography. We also created a water table map and a numerical groundwater flow model of the area.

The EM survey shows a high conductivity area in the immediate vicinity of the reloading facility, but background conductivity values in areas outside the facility. These results agree with chloride concentrations in the monitoring wells, which are high within the facility and at background levels outside. The spatial distribution of domestic wells with high salt concentrations is irregular and deeper wells often have higher total dissolved solids. Several domestic wells have high concentrations of sulfate, while monitoring wells installed within the former storage area have low sulfate concentrations. Chloride/bromide ratios show that all groundwater has been impacted by sedimentary basin brines. Water table contours show that groundwater is moving west from the former reloading site and generally not toward the domestic wells. The geochemical results support the geophysics; both suggest that the high concentrations of salt in domestic wells are associated with naturally occurring salt in the underlying Paleozoic bedrock and not from the former road salt storage facility.