Examples of Cleanup Approaches
    Hagen Farm, Dane County, WI

A 10-acre former gravel pit was used for the disposal of domestic and industrial waste materials from the 1950s to the 1960s. The groundwater is close to the surface, and a 3,600 foot volatile organic compound (VOC) plume emanated from it. Contaminants of concern included 1-2-dichloroethene, vinyl chloride, tetrahydrofuran (THF), benzene, xylenes, and toluene. Private wells located in the plume were contaminated with VOCs.

Site stratigraphy consists of 30 to 40-feet of sand and gravel glacial outwash (shallow aquifer) that overlies a sandstone/dolomite bedrock (bedrock aquifer). There is hydraulic connection between the two. The bottom of the main landfill area is in the groundwater.

The remedial goals at the site were to reduce or minimize direct contact with contaminated waste and soils, reduce or minimize release of contaminants to the groundwater, restore groundwater so that contaminant levels meet appropriate federal and state groundwater quality standards, stop the flow of contaminated groundwater downgradient of the site, and prevent the flow of contaminated groundwater to residential wells. (Groundwater ROD dated 9/30/92)

Two smaller disposal areas were consolidated into the largest one, and the area was covered with a protective cap to prevent precipitation infiltration and physical contact. A soil vapor extraction (SVE) system was placed in the waste area to remove volatile organics. A 130 gpm groundwater pump-and-treat system, with extraction wells located on and off site, was constructed. Since THF (concentration of 630 ppm) and other aerobically degradable chemicals were the principal contaminants of concern, a fixed film biological treatment system was chosen to treat the extracted water. Treated water was infiltrated just upgradient from the capped area and captured by the extraction wells to enhance flow under/through the cell. Institutional controls were imposed for as long as needed to maintain protection.

After five years of groundwater extraction and treatment, the plume has been reduced to the small area underlying and just downgradient from the waste cell. The pump-and- treat system has been replaced with a low-flow air sparging system whose purpose is to provide oxygen to the remaining anaerobic part of the plume where in situ biodegradation will destroy any contaminants migrating from under the cell. The SVE system will continue to remove VOCs from both the waste and groundwater beneath the landfill cover. The sparge and vapor extraction systems are expected to continue to function until onsite cleanup goals are met.

The offsite plume has been restored to drinking water standards, the onsite plume has been reduced in size, and an innovative approach with treatment trains has achieved less expensive operation and maintenance costs.

Source Record of Decision (136K/41pp/PDF)
Groundwater Record of Decision (56K/25pp/PDF)
1996 Five-Year Review (87K/8pp/PDF)
2001 Five-Year Review (194K/26pp/PDF)