Technology:
In Situ Soil Flushing - SEAR
- Test area was 20 feet wide by 30 feet long and 20 feet deep
- Solution consisted of a surfactant, calcium chloride, isopropyl alcohol, and water was injected through 3 injection wells at a rate of 0.133 gallons per minute (gpm) per well for 58 days; six extraction wells removed subsurface liquids at a combined rate of 1 gpm
- Above-ground treatment included gravity separation to remove separate phase DNAPLs, pervaporation to remove dissolved-phase contaminants, and ultrafiltration(UF) to reconcentrate surfactant fluid prior to reinjection
- Surfactant flush was followed by a 74 day water flush to remove injected chemicals and solubilized or mobilized contaminants
- Partitioning interwell tracer test (PITT) to demonstrate DNAPL removal and recovery of injected solution
|
Cleanup Authority:
Not identified
Contacts:
ESTCP Project Manager:
S. Luara Yeh, P.E.
Naval Facilities Engineering Service Center
Phone: (805) 982-1660
E-mail: yehsl@nfesc.navy.mil
Demonstration Contact:
Dr. Leland Vane
Pervaporation Team Leader
U.S. EPA National Risk Management
Research Laboratory
Phone: (513) 569-7799
E-mail: vane.leland@epamail.epa.gov | EPA Contact:
Gena Townsend, EPA Region IV
Phone: (404) 562-8538
E-mail: townsend.gena@epamail.epa.gov |
|
Contaminants:
Chlorinated Solvents and Total Petroleum Hydrocarbons (TPH)
- PCE concentrations in groundwater as high as 54 mg/L
- PCE present as DNAPL and Varsol™, a petroleum distillate, is present as LNAPL in groundwater |
Waste Source:
Operation of central dry cleaning facility |
Type/Quantity of Media Treated:
Groundwater
- Shallow surficial aquifer at a depth of 16 to 20 ft; differences in permeability between the shallower, more permeable zone (hydraulic conductivity of 10-4 cm/sec) and the basal low permeability zone ((hydraulic conductivity of 10-5 cm/sec)
- Majority of DNAPL is present in a low permeability silty layer at base of the shallow aquifer; 105 gallons of DNAPL estimated to be present in the test zone |
Purpose/Significance of Application:
Field demonstration of Surfactant-Enhanced Aquifer Flushing (SEAR) surfactant flushing technology for treating PCE and DNAPL in groundwater |
Regulatory Requirements/Cleanup Goals:
Performance objectives established for the demonstration included:
- 96% DNAPL removal efficiency for groundwater remediation
- Remove 95% of extracted contaminant mass with above-ground treatment
- 90% recovery of injected surfactant, isopropyl alcohol, and tracer |
Results:
- A total of 76 gal of PCE were recovered during the demonstration with 32 gal recovered as solubilized DNAPL and 44 gal as free-phase DNAPL
- DNAPL was effectively removed from the more permeable layer (above 17.5 ft bgs) with DNAPL remaining in the lower permeability basal silt layer; DNAPL recovery in more permeable layer -at a rate of 92%-96%; DNAPL recovery from entire test zone (both layers) - 72%; the poor sweep of the surfactants across the lower portion of the contaminated zone was attributed primarily to the permeability contracts between the two zones
- Above-ground treatment system removed > 95% of extracted PCE; surfactant recovery - 77%; injected isopropyl alcohol recovery - 88% |
Cost Factors:
- Total demonstration costs were $3.1 million, including DNAPL source zone characterization, surfactant selection, well field installation, free-phase DNAPL removal equipment, pre-treatment PITT, application of the technology, surfactant regeneration, and indirect costs
- Estimated total costs for full-scale systems were estimated at $1.5 million to treat a 2,500 square foot area, $6.8 million to treat a 0.5 acre area, and $12.8 million to treat a 1 acre area. |
Description:
Marine Corps Base Camp Lejeune, Site 88, Building 25 is the location of a central dry cleaning facility. The site is contaminated with PCE and Varsol™, a petroleum distillate from storage and use during drycleaning operations. PCE is present in groundwater at the site as DNAPL. Varsol™ is present as LNAPL. A demonstration of the surfactant-enhanced aquifer remediation system (SEAR) was performed by the U.S. Department of Defense Environmental Security Technology Certification Program (ESTCP), targeted at treating DNAPL in groundwater.
Injection of a solution of surfactant, isopropyl alcohol, and calcium chloride was conducted for 58 days, followed by a 78-day water flushing to remove mobilized contaminants and residual flushing solution. DNAPL was effectively removed from the more permeable layer (above 17.5 ft bgs) with DNAPL remaining in the lower permeability basal silt layer. The results of the demonstration showed that aquifer heterogeneity has a strong influence on the performance of SEAR and the sensitivity of the technology to permeability contrasts indicated the importance of performing a thorough DNAPL source zone characterization. |
