Former Dry Cleaner

Project Summary

At a former dry cleaner site in San Rafael, California, an in situ chemical reduction (ISCR) remedy was implemented to address chlorinated volatile organic compound (CVOC) contamination associated with a source release area and the resulting large dilute 3,000 ft long plume. The site was identified as a California Regional Water Board site under the Spills, Leaks, Investigation & Clean-Up (SLIC) Program in 2007.

Off-site impact characterization was performed in 2013 under the direction of San Francisco Bay Regional Water Quality Control Board (SFBRWQCB). The investigation identified an area impacted by constituents of concern (COC) that were detected in groundwater up to a half mile east of the source area. The saturated sand zone encountered between approximately 15 and 25 feet below ground surface (ft bgs) appears to be the principal groundwater bearing unit with COC impacts. A Provect-IR® pilot injection program was proposed and implemented in a portion of the downgradient plume area during 2017. Following the successful pilot test implementation and additional site characterization activities, full-scale Provect-IR® injections were performed both on-site and off-site during 2021 and 2023.

Pilot Permeable Reactive Barrier Program

In July 2017, a permeable reactive barrier (PRB) pilot test was conducted in the downgradient portion of the plume that included 6,800 lbs of Provect-IR® and 8 liters of Dehalococcoides (DHC) inoculum (KB-1, provided by SiREM). The Provect-IR® and DHC were applied via six temporary direct push injection locations. The pilot test PRB was 84 feet in length with an approximate 15 ft vertical target interval from 15 to 30 ft bgs.

Within 8 months following pilot implementation, PCE and TCE groundwater concentrations at MW-10 were reduced to <0.5 µg/L with negative shifts in oxidation reduction potential (ORP) observed.

Full-Scale Remediation Plan

Based on the success of the pilot test, 11 offsite Provect-IR® PRBs and one onsite injection were designed to address the entire plume and target areas with PCE concentrations in excess of 30 µg/L. The PRBs were designed to intersect the large dilute plume and reduce PCE concentrations to below the SFBRWQCB Cleanup Level of 5 µg/L. The target monitoring wells were located 30 to 100 ft downgradient from the Provect-IR® PRBs.

The remedial program was developed by RMD Environmental Solutions Inc. (a subsidiary of Citadel EHS) and Provectus Environmental Products, Inc. with in situ implementation provided by Gregg Drilling. During June through August 2021, a total of approximately 67,900 pounds of Provect-IR® and 77 liters of DHC were injected within 12 strategic areas. PRB lengths varied from 75 to 400 linear ft with vertical injection intervals ranging from 14 to 42 ft bgs.

Due to the success of the 2021 full-scale injection program, an additional Provect-IR® injection event occurred between July and September 2023. The second full-scale phase included a total of approximately 64,750 pounds of Provect-IR® and 66 liters of DHC injected within additional treatment areas.

Treatment Program Results

• Substantial PCE reductions observed across the 3,000 ft plume following Provect-IR® injections.
• Within 20 months of implementation, PCE concentration reductions of >99% were observed in 11 of the 14 target monitoring wells.
• Only one monitoring well within the PRB target area remained above the PCE standard of 5 µg/L.
• The 3,000 linear ft PCE plume no longer exists following full-scale treatment.
• Provect-IR® PRBs were designed to have a lifespan >7 years, with additional CVOC reductions anticipated as biotic and abiotic reactions continue.