EDGERTON SAND & GRAVEL SITE
EDGERTON, WISCONSIN

LBG designed, installed, and is currently operating a soil vapor extraction (SVE) system for the Wisconsin Department of Natural Resources Bureau for Remediation and Redevelopment. This state superfund site consists of an active gravel pit operation, a closed landfill, and a former unregulated burn pit where diseased Dutch elm trees, industrial waste and spent solvents were disposed. The remedial action consisted of capping the burn pit area with a vapor barrier and actively remediating the soil with an SVE system.

In order to maximize the effectiveness of the SVE system, LBG conducted a geophysical survey and a SVE pilot test prior to designing the system. The electromagnetic conductivity survey was performed in the vicinity of the burn pit area to delineate the boundaries and depth of the former burn pit, which had been filled. The survey resulted in increasing the proposed project area by 15 percent.

A SVE pilot test was conducted on two nested wells. The test was conducted to confirm that SVE was the appropriate remedial technology, to determine the vacuum required to extract maximum air flow from the formation, to determine the radius of influence, and to obtain data needed to estimate emission rates.

The vapor barrier was installed to minimize short circuiting of the SVE system and to reduce leaching of contaminants to ground water. The 80,000 square foot barrier consists of a low-denisty polyethylene geomembrane liner, a composite drainage fabric, and a geotextile protective cover over the liner.

The soil vapor is extracted by two regenerative blowers at a rate of 1,000 scfm. Approximately 4,900 pounds of VOCs have been removed by the SVE system during the first year of operation.

During the installation of the SVE wells, LBG discovered free-phase product at the site. Previous investigations conducted by other consultants had not identified product at the site. Over 2.5 feet of product has been observed in one of the wells. LBG researched various product recovery techniques and has recently installed a belt skimmer in one of the deep SVE wells. The skimmer is programmed to operate one-half hour per day to recover the highly viscous product.

System Flexibility

• The blower configuration is designed to allow for parallel operation, series operation, or reverse air flow.
  
  
• Each well is piped directly to a header in the remediation building. In the building, the piping is configured to allow each well the capability to operate as an air inlet well.
  
  
• The sixteen SVE wells were installed in nested clusters consisting of a shallow and deep well.
  
  
• With the SVE piping configuration, air flow patterns throughout the burn pit can be easily manipulated to target hot zones or dead zones by operating select deep or shallow wells under vacuum or as air inlets.