SCH Number 2016071052

Project Info

Title

Removal Action Workplan for Calsol Site

Description

DTSC is proposing to approve a removal action workplan pursuant to chp 6.8, division 20, section 25323.1 and 25356.1 of the CA Health and Safety Code for the former Calsol facility, hereinafter referred to as the "Subject Property". The subject property and impacted off property area will be hereinafter referred to as the site. The RAW addressed volatile organic compounds (VOCs), primarily tetrochloroethylene (PCE) and trichlorethylene (TCE) in the soil and soil vapor located beneath the Site. PCE and TCE are the two primary Chemicals of Concert (COCs) in the soil, soil vapor, and groundwater for the Site, and although other VOCs were detected in soil vapor and groundwater at the Site, PCE and TCE have been detected at the highest concentrations. The RAW evaluated remediation alternatives and identified a preferred action to accommodate the planned urban plaza or open space land use. The remediation activities includes: 1) Soil Vapor Extraction Well (SVE) Installation: Two triple nested SVE wells are planned to be installed at the Subject Property in conjunction with the existing SVE system. 2) Soil Vapor Monitoring Probes: Four triple nested soil vapor monitoring probes will be installed at the Subject Property. 3) SVE system operation and maintenance: SVE system will be maintained in accordance with the manufacturer's recommendations. 4) Post SVE confirmation sampling: Confirmation soil vapor and soil sampling will be conducted to further assess the effectiveness of the SVE system. 5) In Situ Chemical Oxidation (ISCO) Implementation (Optional): If post SVE confirmation sampling identifies VOC concentrations exceeding the Removal Action Goals for OU-1, ISCO technology will be implemented to further reduce VOC soil concentrations. 6) Soil Vapor Monitoring: Soil vapor sampling is planned to be conducted prior to starting the SVE system and quarterly thereafter. 7) Indoor Air Sampling: Additional indoor air sampling will be performed in homes near the Subject Property to determine if a potential risk of vapor intrusion exists. Further indoor air sampling is proposed when soil gas monitoring indicates elevated concentrations which may pose a health risk to the occupants. 8) Sub-slab depressurization system: If indoor air concentrations pose an unacceptable potential health risk, a sub-slab depressurization systems is proposed to be installed at homes requiring mitigation. 9) Groundwater monitoring: Quarterly monitoring will be conducted to assess current impact to groundwater and determine remediation options. 10) SVE decommissioning: When the remediation is complete, SVE wells are planned to be decommissioned appropriately after approval from DTSC. 11) Soil Vapor Probe Decommissioning: When the remediation is complete, soil vapor probes are planned to be decommissioned appropriately after approval from DTSC.

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