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• • EDMUND O.BROWN JP. } OOVEnXOP AT'HM RIQUEZ pALIFp11M1• FRErlLxva oL Exn orRmecuoN Water Boards Central Valley Regional Water Quality Control Board 14 July 2016 Nichole Gleason Robinhood Plaza Shopping Center, LLC 621 Capitol Mall, Floor 18 Sacramento, CA 95614 WORK PLAN FOR SUB-SLAB VENTING AND SVE WELL ABANDONMENT, C&S ONE HOUR MARTINIZING FACILITY AT ROBINHOOD PLAZA, SAN JOAQUIN COUNTY Central Valley Water Board staff has reviewed the 13 July 2016 Work Plan to Install a Sub-Slab Venting System and Abandon Soil Vapor Extraction Wells (Work Plan) for the C&S One Hour Martinizing Facility submitted by Terraphase Engineering Inc. on behalf of Robinhood Plaza Shopping Center, LLC. The Work Plan was submitted pursuant to our discussions with you during a 24 February 2016 meeting. Central Valley Water Board staff also reviewed a draft version of the Work Plan and it was modified in this final version to include venting between the wall and the dry cleaning machine following further discussions during a 6 July 2016 meeting and an 11 July 2016 site visit. The Work Plan proposes to install a passive sub-slab venting system and to abandon three of the four soil vapor extraction (SVE) wells (EX-2 through EX-4) and the five soil vapor probes (SVP-1 through SVP-5). The SVE wells will be abandoned by in accordance with permits from San Joaquin County Environmental Health, and the soil vapor probes will be abandoned by sealing with grout to flush grade. As shown in Figures 3 through 5 of the Work Plan, the sub-slab venting will consist of 1-inch diameter schedule 80 PVC pipes that include a slotted section next to the dry cleaning machine and that connects to 1-inch diameter slotted stainless steel piping along the wall. A separate 1-inch pipe will be connected to EX-1. Both pipes will run underneath the slab to the exterior of the building, then underneath the side walk and up the side of the building to a passive turbine vent. The pipes that run up the side of the building will be covered with a rain gutter downspout or similar covering that will be painted to match the building. Trenching for the piping will be performed by saw cutting through the concrete slab and digging to approximately 7 inches below the slab. The slotted steel pipe next to the wall will be installed by driving the pipe directly into the sub-slab gravel. After the piping is installed and backfilled, a heavy plastic liner or geotextile fabric will be placed above the bedding material and concrete will be poured and finished to match existing grade. Excavated soil will be stored on-site in a secure location in 55-gallon drums for characterization and proper disposal at a landfill. Central Valley Water Board staff concurs with the work proposed in the Work Plan. As proposed, a report must be submitted documenting completion of the work at which time a request for No Further Action can be made. The No Further Action request must include a trend analysis similar to the 15 March 2016 draft Trend Analysis technical memorandum , and include discussion of previous remedial efforts, protection of human health, and water quality data from previous investigations at the KARL E. LONOLEY SCD, P.E.,CHAIR I PAMELA C. CREEOON, EXECUTIVE OFFICER 11020 Sun Center Drive#200,Rancho Cordova.CA 95670 I www.waterboards.ca.gov/centralvalley L',PCYCLED 1I a