Terraphase is managing a chlorinated volatile organic compound (VOC) assessment and remediation project at a former metal manufacturing facility. Following the completion of groundwater and soil vapor remediation, the project has entered the post-remediation monitoring phase. Despite previous cleanup efforts, sub-slab vapor concentrations of chlorinated VOCs remained above regulatory screening levels, prompting further evaluation for vapor intrusion risks.

Scope of Services

Terraphase is currently assessing potential vapor intrusion by collecting paired sub-slab vapor and indoor air samples and conducting human health risk assessments on a building-by-building basis.

In one facility, elevated indoor vinyl chloride concentrations—absent in sub-slab vapor—prompted a focused assessment to identify the source. Terraphase repurposed an existing soil-vapor extraction (SVE) blower with carbon abatement as an interim sub-slab depressurization system (SSDS) during site closure negotiations with the Los Angeles Regional Water Quality Control Board (RWQCB).

Notable Accomplishments

• Completed groundwater and soil vapor remediation and transitioned to post-remediation monitoring
• Performed detailed vapor intrusion risk assessments across multiple buildings
• Identified and traced unexpected indoor air vinyl chloride concentrations
• Used targeted field screening and lab analyses to confirm indoor air quality sources
• Installed an interim SSDS using existing infrastructure to support site closure negotiations with RWQCB
• Leveraged a permit exemption from the South Coast Air Quality Management District by repurposing the existing SVE equipment and installing shallow SSDS sumps, saving tens of thousands of dollars per year in permit fees and monitoring expenses