In Situ Biosparging of a Large Scale, Dissolved Petroleum Hydrocarbon Plume at a Southwest Lumber Mill, 1997 Environmental Conference Proceedings

In 1989, a lumber mill in east-central Arizona discovered approximately 25,000 gallons of gasoline had been released from their fueling system. Soils near the fueling system area were remediated through excavation and on-site land farming. Impacted groundwater was addressed through pump and treat technology. A pilot test indicated that aquifer cleanup could be accelerated for significantly less cost than the pump and treat system. which would no longer be required. In May 1996, an air sparge system was installed. The air sparge system was designed to supply low air flow (2 to 10 cfm) to each wellhead, providing a mechanism for the indigenous microbial community to receive additional oxygen. The installed system contains 89 sparge wells divided into eight lines, and three vapor extraction wells for vapor control. The sparge lines were operated continuously for the first three months before changing to a manually-switched 12-hour rotating schedule. The soil vapor extraction wells are operated continuously. with direct discharge of the vapors. October 1995 pre-test total BTEX concentrations ranged from 157 to 11,510 µg/L Contaminant concentrations had declined in June 1996 ranging from 40 to 97 percent of initial concentrations,