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Case Study #5

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Remedial Case Study

Overview:

NAPL (Non Aqueous Phase Liquid) determined to be gasoline was encountered at various groundwater wells during site investigation activities. LEI removed the NAPL via a vacuum truck. LEI then conducted additional assessments resulting in the design and installation of a soil vapor extraction (SVE) system acting in concert with air sparging (AS). During SVE/AS system operation, LEI staff identified an on going release from the stage II system due to vapor concentration variations coincident with gasoline deliveries. The stage II line was repaired by a pump and tank contractor. Final clean up goals were met by polishing off target areas with 2 chemical oxidation (Chemox) injection events.

Assessment:

The following assessment activities were performed during the initial site investigation and the selection and design of the remedial systems:
  • Developed health and safety plan
  • Advanced 4 soil borings via Earth Probe direct push techniques and completed borings as microwells
  • Collected, field screened, and lab analyzed select soil and groundwater samples
  • Encountered NAPL up to 1.5″
  • Conducted additional soil investigation via a portable rotary hammer equipped with 2″ augers

Response Activities:

Response activities included separate actions taken to address the NAPL and the residual petroleum constituents in soil and groundwater. These activities included the following:
  • Supervised extraction of 1,000+ gallons of gasoline and water to address the free phase gasoline
  • Designed and installed an SVE/AS system consisting of 6 nested SVE/AS wells
  • Operated SVE/AS system for approximately 18 months
  • Designed a Chemox remediation program for final site polish utilizing existing site wells as injection points
  • Conducted 2 Chemox injection events in July 2000
  • Monitored air and groundwater for key parameters during injection events
  • Conducted post injection groundwater sampling to confirm the return to baseline conditions
  • Prepared a Method 1 Risk Assessment indicating that No Further Remedial Actions were needed at this property

Key Monitoring Results:

Current Site Status:

  • Site Closed — No Further Remedial Actions required
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