RANCOUR PROPERTY SITE REMEDIATION
Abstract:After a decade of site investigation, studies, design, and remediation, the cleanup of contaminated soils and groundwater at a site in downtown Reed City, MI is virtually complete, finally positioning the property for redevelopment. Working for the Michigan Department of Environmental Quality (MDEQ), Malcolm Pirnie, Inc. was responsible for successfully conducting the project in several phases, specifically designed to prevent uncontrolled release of contaminants in this residential and commercial area.
In 1986, during excavation activities for construction of a bank, soil and groundwater contamination was discovered in this urban community in northwest Michigan. This site, known as the former Rancour Manufacturing property, had previously been the location of a metalworking and automotive parts manufacturing facility that had been demolished as part of the downtown redevelopment activities. Soils saturated with a waste oil-like substance were found in an interval above the water table, and halogenated volatile organic compounds (VOCs) were discovered in the soil and groundwater.
To determine the extent of soil and groundwater contamination and define hydrogeologic conditions controlling the migration of VOCs at the site, Malcolm Pirnie conducted a remedial investigation beginning in 1991. Pilot scale and bench scale treatability studies were subsequently conducted to provide a basis for the design of the selected remedial alternative components.
Because of the site's location in a residential and commercial area near the city center, components of the selected remedial alternatives were implemented in a sequence designed for maximum protection of the public. During the first phase of work, lead-contaminated surficial soil was removed to eliminate this direct-contact hazard and to prevent the spread of contamination when heavy equipment was brought on-site to conduct subsequent work phases.
During the next phase, soil vapor extraction (SVE) technology was employed to remove VOCs from vadose zone soils. The use of SVE allowed removal of VOCs without physical disturbance of the soils, preventing the uncontrolled release of VOCs to the atmosphere and exposure of the community.
The next step, removing waste oil saturated soils from just above the water table, was conducted to halt the ongoing release of VOCs to the groundwater. Direct excavation of the contaminated soils was chosen as the most cost-efficient, timely method for removal, due to the relatively shallow depth to the water table. The success of this approach was documented by the hundred-fold decrease in VOC concentrations at the hydraulically downgradient boundary of the site during the two years following the free phase product removal. It also enabled the final project phase, groundwater remediation, to be completed a much shorter timeframe and at less cost than would otherwise have been possible.
Groundwater remediation, the last phase of site cleanup, presented an unusual challenge. The contaminant plume was found to be migrating beneath a State highway, which serves as the primary route for commercial truck traffic through the city, and toward a food production and packaging and distribution facility. This posed a very difficult issue of how to reach the contaminant plume without digging up the highway and disrupting traffic and commercial operations in the city.
Pirnie's solution involved a technology unprecedented in Michigan for this purpose – drilling a horizontal groundwater collection well underneath the highway. Drilling the borehole for the horizontal well installation was complicated by underground utilities located beneath the highway. The well screen was installed along the long axis of the plume beneath the highway, but the presence of a food production facility across the highway from the site made it impossible to complete the boring in a straight line. Consequently, the boring was curved with the exit hole located at a 45 degree offset from the initial line.
This innovative well design approach not only avoided the need for construction activities on the State highway, which would have disrupted traffic and commerce, it also allowed capture of the plume at a pumping rate less than half the rate that would have been required for plume capture by a system of conventional vertical wells. This allowed the treatment facility to be downsized and thus resulted in a much lower life-cycle cost of groundwater collection and treatment.
A “hybrid” UV/peroxide advanced oxidation process (AQP) treatment process was chosen to destroy contaminants in the groundwater pumped from the horizontal well to an aboveground treatment facility. After addition of hydrogen peroxide to the groundwater, water passes through a cell where UV light catalyzes the formation of hydroxyl radicals, which in turn react to destroy the organic contaminants, forming innocuous oxidation products (carbon dioxide and water). An innovative process employing specialized granular activated carbon (GAC) was used to destroy residual peroxide to comply with permit requirements for discharge to a nearby river..
Document Type: Research Article
Publication date: January 1, 2003
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