Salt Runoff and Discharge Impacts on Groundwater and Surface Drinking Water Supply – Eagle Creek Reservoir

Challenge

The discovery of petroleum-impacted groundwater from an underground storage tank release at an Indianapolis Department of Transportation  facility adjacent to Eagle Creek Reservoir in Indianapolis, Indiana called for the design and installation of a groundwater recovery and treatment system to halt further discharge into the reservoir. The pump and treat system was designed to remove the organic constituents prior to discharge to the reservoir. However, the existence of high concentrations of chloride due to salt release from an existing on-site storage area was a human health and aquatic environment concern since the reservoir is used as a principal source of the City of Indianapolis’ drinking supply and a major natural habitat for fish and wildlife. NPDES permitting required a quantitative evaluation of these impacts.

Action

To estimate chloride concentrations migrating to Eagle Creek and total salt loading to the reservoir, Mundell personnel completed both surface water and groundwater modeling, chemical transport analyses, and field measurements of chloride concentrations and specific conductance to determine the expected level of impact near the site bank and discharge areas.

Results

The modeling results were calibrated with the site-specific measurements and shown to be a reliable indicator of future expected impacts to surface water quality. The results of the study indicated that the chloride concentrations released near the bank adjacent to the Trader’s Point facility would be only slightly elevated above current background levels and that existing plant and animal species living in Eagle Creek would not be impacted.