Tuesday, November 6, 2007 : 3:20 p.m.
Multiple Cell Six-Phase Heating for DNAPL Removal
Full scale six-phase heating (SPH) is being performed at Alameda for DNAPL source removal within the 10,000 micrograms per liter (µg/L) total contaminants of concern (COCs) contour of three separate plumes. The principal COCs are 1,1-DCE, 1,1-DCA, and 1,1,1-TCA.
SPH was successfully applied at the 1/3 acre area of Plume 5-1 in 2004. Parallel operation of adjacent SPH cells was used for interstitial area heating through electrical cross talk. Multiple piece electrodes were utilized for increased surface area and driven sheet-pile electrode members resulted in a substantial cost savings. Average groundwater concentrations were reduced from 54,000 µg/L to less than 100 µg/L with minimal rebound 4 months later. More than 3,000 pounds of VOCs were recovered.
Removal operations are currently ongoing at Plumes 5-3 and 4-2, each roughly an acre in area. The designed system at 5-3 follows that used at 5-1, consisting of five standard SPH cells, each six electrodes arranged in a hexagonal pattern with a neutral electrode at its center, installed to depths up to 20 feet. The first of three operational stages at Plume 5-3 was completed in December 2006, removing over 250 pounds of VOCs and reducing groundwater concentrations from 100,000 µg/L to less than 400 µg/L. The two remaining stages will each require 3 months of heating with 1 month for relocation, beginning in May 2007.
At Plume 4-2, the entire area is being treated in one operation. Ninety-one electrodes, consisting of a steel pipe set within conductive backfill, were installed by HSA to depths up to 45 feet and set on 20-foot spacing. Operations began in October 2006 and to date have resulted in greater than 150 pounds of VOC removal and groundwater concentration reductions from 400,000 µg/L to less than 6,000 µg/L. Operations will continue until asymptotic removal is achieved.
SPH was successfully applied at the 1/3 acre area of Plume 5-1 in 2004. Parallel operation of adjacent SPH cells was used for interstitial area heating through electrical cross talk. Multiple piece electrodes were utilized for increased surface area and driven sheet-pile electrode members resulted in a substantial cost savings. Average groundwater concentrations were reduced from 54,000 µg/L to less than 100 µg/L with minimal rebound 4 months later. More than 3,000 pounds of VOCs were recovered.
Removal operations are currently ongoing at Plumes 5-3 and 4-2, each roughly an acre in area. The designed system at 5-3 follows that used at 5-1, consisting of five standard SPH cells, each six electrodes arranged in a hexagonal pattern with a neutral electrode at its center, installed to depths up to 20 feet. The first of three operational stages at Plume 5-3 was completed in December 2006, removing over 250 pounds of VOCs and reducing groundwater concentrations from 100,000 µg/L to less than 400 µg/L. The two remaining stages will each require 3 months of heating with 1 month for relocation, beginning in May 2007.
At Plume 4-2, the entire area is being treated in one operation. Ninety-one electrodes, consisting of a steel pipe set within conductive backfill, were installed by HSA to depths up to 45 feet and set on 20-foot spacing. Operations began in October 2006 and to date have resulted in greater than 150 pounds of VOC removal and groundwater concentration reductions from 400,000 µg/L to less than 6,000 µg/L. Operations will continue until asymptotic removal is achieved.
David A. Cacciatore, Ph.D., PE, Shaw Environmental Inc. Cacciatore, David, Ph.D., P.E., is a Senior Engineer with the Federal Technical Services Group of Shaw Environmental, Inc. in Concord, California. He has more than 14 years of experience in air, water and soil remediation technologies. He has served as a project manager, technical lead, and engineering task manager on federal programs evaluating, designing, and implementing innovative technologies for DNAPL removal and remediation at former Navy installations, including six-phase electrical resistance heating, chemical oxidation, and in situ bioremediation. He holds degrees in chemical engineering (Ph.D. and M.S.) and chemistry (B.S.).