First State-funded cleanup using electrical resistivity heating technology

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Courtesy of TRS Group, Inc.

The Remediation and Redevelopment Division (RRD) completed remediation at a former dry cleaning facility in the city of Owosso using electrical resistivity heating (ERH) technology. Electrical resistivity heating is an in­situ electrical heating technology that uses electricity and applies it into the ground through electrodes. The resistance of the electricity traveling through the ground creates heat that will vaporize volatile organic compounds. These vapors are collected and treated through a vapor extraction recovery system.

The remediation site, former Launderama Dry Cleaner’s site, located in the city of Owosso’s downtown business district, is the current location of an operating medical center and restaurant. In 2004, the RRD discovered perchloroethylene (PCE), a common dry cleaning compound, in the soil and groundwater beneath the restaurant and medical center. The levels of PCE were such that they not only created an indoor air threat to the tenants, but also infiltrated a storm sewer that discharges to the nearby Shiawassee River. Portable air purifying units were installed in the buildings to reduce indoor air concentrations to acceptable levels as an interim response action. In 2011, the State of Michigan contracted with Stantec, Inc. and Thermal Remediation System Group to conduct remediation under the medical center and restaurant using ERH technology.

Construction of the thermal remediation system commenced in October 2011 and consisted of drilling 83 borings to a depth of 14 feet and installing electrodes in each boring. Several piezometers and temperature probes were installed to monitor the pressure and temperatures in the subsurface during remediation. The electrodes were connected to a central power control unit. Each electrode location also contained a vapor extraction well that was connected to a vacuum to extract and treat vapors generated during the thermal remediation process. During the first two weeks of construction, the restaurant’s dining room area was closed to conduct the installation of the ERH system. The entire ERH system in the restaurant was installed below grade, and the dining room area was reopened during the remainder of system construction and operation.

On January 9, 2012, the ERH system was put into operation. The goal was to heat the soil and groundwater to a temperature of 88 degrees Celsius, and then run the system for 77 days at which time the PCE would completely volatize, and the vapors would be extracted and treated. The 88 degree temperature was obtained on March 9, 2012, and the ERH system operated until June 7, 2012, at which time the system was decommissioned. A total of 821 pounds of volatile organic compounds were removed during remediation.

Initial verification sampling conducted in July 2012 has indicated more than a 90 percent reduction in soil concentrations under the medical center and restaurant. Additional soil gas monitoring and verification sampling will continue until the end of 2013.

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