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Abstract

In March 1986, during installation of a monitoring well at an industrial electroplating facility a chrome rinse line was pierced by an auger. A six-inch recovery well was installed in the borehole at the release point and the recovered groundwater was pumped directly into the facility’s wastewater treatment plant. In 1998, a site assessment identified elevated hexavalent chromium concentrations in groundwater in this area of the site. The assessment included the installation of monitoring wells which were sampled over several years. The data indicated that the concentrations in this area of the site were increasing. Additional investigations, conducted upgradient of the process line release, identified another source of hexavalent chromium – one of the platers inside the building.

A remediation system was designed to remediate the hexavalent chromium release which included the installation of five recovery wells and associated piping. In Fall 2006, step tests were conducted to determine the approximate pumping rate for the recovery wells. Based on the results of the test, pumping rates of up to four gallons per minute were included in the design.

A pilot test was subsequently conducted to confirm that the proposed treatment process, utilizing ion-specific exchange filters, was appropriate for the removal of hexavalent chromium and nickel. In addition, the data from the pilot test was used to determine the anticipated frequency of greensand filter backwash and change-out frequency for the resin containing hexavalent chromium.

The system was installed during Spring-Summer 2008 and includes three hexavalent chromium-specific resins and two nickel-specific resins in a remediation building at the site. The majority of the treated effluent is recharged upgradient of the system into a recharge pit to enhance flushing of the aquifer. The remainder of the treated effluent is discharged to the municipal sewerage system under an Industrial Pretreatment Permit.

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