Former Dry Cleaner Site Investigation, Remediation, and Mitigation System Installation

Terraphase was retained to implement remedial activities at a former dry-cleaner site in Southern California impacted by volatile organic compounds (VOCs), including tetrachloroethene. Terraphase was tasked with achieving the site’s remedial objectives more efficiently and cost-effectively, while addressing data gaps and optimizing the original strategy.

Scope of Services

Terraphase performed additional site investigation to address data deficiencies and subsequently refined the originally proposed remedial approach. This included revising the soil-vapor extraction (SVE) system design, expanding the soil-gas monitoring infrastructure, and targeting vapor sampling across the former dry-cleaning site and adjacent units. Our team installed five multi-depth soil-gas monitoring points and two dual-nested SVE wells. A pilot test confirmed the feasibility—but limited mass removal potential—of SVE. Based on these results, Terraphase designed and implemented a sub-slab depressurization system (SSDS) as a long-term mitigation strategy. The SSDS consisted of a horizontal SVE line beneath the slab, connected to a rooftop automated blower system with telemetry and vapor treatment using granular activated carbon.

Notable Accomplishments

  • Closed data gaps through targeted additional site investigation
  • Optimized and implemented a more effective SVE system design
  • Installed five soil-gas monitoring points and two dual-nested SVE wells
  • Conducted SVE pilot testing to confirm performance and limitations
  • Designed and installed a cost-effective SSDS beneath the former dry-cleaner site
  • Reduced the client’s annual operating costs from ~$150,000 to under $2,000
  • Delivered a regulatory-approved system currently in operation

Christopher Alger, PG, CHG, CEG

Senior Principal Engineering Geologist

Christopher’s Profile