Nashville, Tennessee

Background

The subject site was selected by the Tennessee Department of Environment and Conservation to test the effectiveness of EcoVac Services’ patented SURFAC^® process and remove gasoline/diesel fuel.  Little background information was obtained prior to SURFAC^® due to the client’s computer files being destroyed.  Mobile-phase extraction events and SPH skimmers had been previously utilized to remove SPH from the site.

The object of EcoVac Services’ patented SURFAC^® process was to remove all SPH from the site. 

Geology/Hydrogeology

Groundwater is present in limestone at depths ranging from 3 to 35 feet below grade.  Limestone is present at approximately 2 feet below grade.

Treatment Methodology

EcoVac Services was contacted to implement SURFAC^® at this site due to the challenging subsurface conditions (i.e. fractured limestone bedrock) and the failure of previous remedial activities.

EcoVac Services’ patented SURFAC^® process is the combination of dual-phase/multi-phase extraction and surfactant injection.  The process described herein is patent-protected and represents the intellectual property of EcoVac Services, Inc.

SURFAC^® Pilot Test

A one-day SURFAC^® pilot test was conducted at the site to: (1) achieve contaminant removal, (2) reduce the aerial/vertical extent of the plume, (3) locate fractures/joints and depth(s) of contamination for proper placement of the surfactant, (4) determine the surfactant injection volumes/locations/sequence, and (6) determine the duration of the surfactant injection/capture events.

Historically, SPH had been present in two monitor wells ranging up to 5 feet in thickness.  The SURFAC^® pilot test was conducted at two monitor wells.  Stinger (drop tube) depths were increased throughout the event to identify fractures/joints and depth(s) of contamination.  Fractures/joints were identified during the test by higher flow rates and lower in-well vacuums at certain stinger depths.  Hydrocarbon removal rates increased when these fracture/joints were contacted, indicating these fracture/joints acted as preferential pathways for fuel migration and accumulation in the subsurface.  The dewatering of the aquifer during the pilot test exposed “trapped” SPH and mobilized it to MW-9. 

SURFAC^® Treatment Program

SURFAC^® was conducted at the subject site during a one week period in September 2005.  The pilot test had mobilized SPH (0.25 feet) into one well prior to SURFAC^®.  The aquifer was dewatered during SURFAC^® to expose the SPH “trapped” in the fractures/joints identified during the pilot test and ensure the injected surfactant came into contact with the SPH. Mobilized SPH was subsequently “captured” with mobile dual-phase/multi-phase extraction.

Results

SITE CLOSURE WAS ACHIEVED.