|Ecovac Services / Projects / Solvent /|
Site Location: Macon, Georgia
Site Use: Prior dry cleaners site
Geology: clayey-silty sand on top of bedrock
Depth to Water: 35 – 50 feet
Initial Plume Dimensions (dissolved PCE >MCLs): ~300 ft x 500 ft
No. of Wells > MCLs: ~10
PCE Concentrations: 1,200 ug/l maximum
A plume from a former dry cleaners site from decades ago has emanated a ~300 feet by ~500 feet PCE plume. Remediating the plume will be complicated by topographic differences, access, and the existence of several roads and buildings.
EcoVac Services implemented a two day ISCO-EFR® pilot test on the four source area compliance wells in February of 2008. This short term pilot test yielded a 37% to >95% reduction in PCE concentrations in the four wells compliance monitor wells within the test area. In November of 2009 twelve injection wells (four shallow and eight deep wells) were installed around the compliance wells to be used for ISCO-EFR® implementation. During the well installation phase Shelby Tube samples and groundwater samples were collected for EcoVac to perform a Treatability Study including Soil Oxidant Demand and full scale design parameters. This study is currently ongoing and will be completed in February of 2010 after which ISCO-EFR® will be implemented for source area remediation.
EcoVac Services performed pilot testing on the new injection wells in December of 2009. Results of the second round of pilot testing include the removal of 482 pounds of PCE (23 equivalent gallons) and 2,076 gallons of impacted groundwater. During these tests groundwater drawdown and vacuum response were measured on surrounding injection wells and compliance wells to better understand the connectivity and flow paths in the vadose and saturated zones.
The four shallow vadose injection wells were installed in the area where the PCE tank formerly existed to allow for emplacement of oxidants into the impacted soil horizon above the water table which exists approximately 50 feet below the land surface. The highest PCE concentrations in the groundwater have been found slightly upgradient of the former tank location and it was assumed that the released PCE liquids had migrated laterally to reach that location.
Pilot testing of the shallow vadose injection wells showed a strong vacuum influence on the highest concentration compliance well indicating that a preferential pathway for migration of contaminant did exist and could be utilized during the upcoming ISCO-EFR® remediation phase by extracting on the compliance well while injecting the shallow injection well. Extraction on the deep injection wells produced drawdown on the compliance well but showed very little vacuum influence even though they were very close to the compliance well and will be useful to treat the dissolved contaminants in the saturated zone.