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770-592-1001
| Ecovac Services / Projects / Railroad / |
Memphis, Tennessee
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SITE LOCATION: |
Memphis, Tennessee (Rail Yard) |
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PLUME DESCRIPTION: |
Two SPH plumes in shallow perched zones and one SPH plume in the underlying fluvial aquifer. |
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HYDROGEOLOGY: |
Lithology is highly variable. Shallow perched zone is present at approximately 10 feet and consists of fill (cinder), sand, and silty clay. The underlying fluvial aquifer is present at approximately 30 to 35 feet below grade in poorly graded sand with gravel at depth and is confined by an overlying clay |
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EFR® EFFECTIVENESS: |
EFR® has removed approximately 2,232 gallons of diesel fuel at the site |
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PROPOSED APPROACH |
Utilize SURFAC® for one of the shallow perched zones. Continue with enhanced fluid recovery (EFR®) in the area of the other shallow perched zone plume and fluvial aquifer until these areas are further delineated and mass removal rates have decreased. Implement SURFAC® once the SPH thicknesses are abated. |
Background
EcoVac Services was retained to remove SPH from two shallow perched zone plumes and one underlying fluvial aquifer plume. SPH has been present in the shallow perched zone to thicknesses up to 1.08 feet. Up to 15.38 feet of SPH has been detected in the fluvial aquifer. A remediation system consisting of two recovery wells containing skimmer pumps has recovered approximately 90 gallons of SPH in two years at a capital/O & M cost of $70,000 ($778/equivalent gallon of diesel fuel removed).
Geology/Hydrogeology
The site consists of a shallow perched zone at about ten feet below grade. In-well vacuums (14 to 23 inches of mercury) collected during extraction from the shallow perched zone wells (MW-7, MW-13, and RW-1) and boring log descriptions indicate relatively low permeability in this zone. Boring logs describe the shallow subsurface as fill material, sand and silty clay.
The underlying fluvial aquifer is present at approximately 25 to 35 feet below grade in poorly graded sand with gravel at depth. Overlying clay appears to confine this aquifer. Fluvial aquifer wells are screened in the poorly graded sands. Extraction from monitor wells screened in the fluvial aquifer indicates variable permeability in the poorly graded sands. In-well vacuums produced during extraction ranged from 1 to 21 inches of mercury.
Treatment Methodology
EcoVac Services has implemented EFR® (mobile dual-phase/multi-phase extraction) at the site for mass removal of diesel fuel. EFR® simultaneously removes vapors, SPH, and groundwater from the subsurface.
SURFAC® is proposed for one of the shallow perched zones after EFR® has reduced SPH thicknesses from 1.08 to 0.02 feet. SURFAC® is proposed for the fluvial aquifer and other shallow perched zone once mass removal rates have decreased and the plumes have been further delineated.
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.
Results and Conclusions
EFR® has removed approximately 2,232 gallons of SPH from the site at a cost of $84,263 ($36/equivalent gallon of diesel fuel removed, compared to $778/gallon for the previous skimmer pump removal method).
