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In June and August 2021, PCE was reported up to 4.5 µg/m3 in the indoor air samples collected by the <br /> RWQCB. Laboratory reports and associated review memos for these indoor air sampling results have been <br /> uploaded to GeoTracker for this case (#T10000017178). <br /> Figure 4 shows the proposed passive soil gas locations; however, locations will be confirmed based on <br /> data collected during the utility location and sewer inspection tasks and discussed with the RWQCB. Soil <br /> gas sampling will be conducted in accordance with the Draft Supplemental Guidance: Screening and <br /> Evaluating Vapor Intrusion (DTSC/California State Water Resources Control Board [CASWRCB] 2020) and <br /> the Advisory,Active Soil Gas Investigation(California Environmental Protection Agency, DTSC, Los Angeles <br /> RWQCB, San Francisco Bay RWQCB, 2015). <br /> APTIM will use the Beacon BESURE Sample Collection KitsT°" (Beacon) to collect passive soil gas. Up to 28 <br /> Beacon samplers will be installed at the Site and the three residential properties. The Beacon samplers <br /> will be installed at a depth of approximately three feet bgs. <br /> The Beacon sample locations will be based on review of utility locating results and video assessment of <br /> vicinity sanitary sewer laterals. It is anticipated that Beacon samplers will be installed along the sanitary <br /> sewer lateral exiting the former Ripon Cleaners building, at locations of possible sewer line disconnects <br /> or identified leaks, and near other potential utility corridors. Beacon samplers installed at residential <br /> properties will be located adjacent to the exterior walls of each home. One Beacon sampler will be <br /> installed adjacent to each residence's private sanitary sewer lateral to assess whether the sewer lateral is <br /> a conduit of potential VOC migration. The RWQCB will share sample results with residents at the <br /> completion of passive soil gas sampling. To protect residents' privacy, residential properties are not <br /> identified on Figure 4 and omitted from work plan text. <br /> The Beacon Samplers will be deployed for 14 days; however,each location will be screened for VOCs using <br /> a low level photoionization detector(PID).The PID readings will be noted on sample collection forms and <br /> reviewed to confirm the length of deployment. Locations where readings exceed 5 parts per billion by <br /> volume may be deployed for a shorter time interval to avoid oversaturation of the sorption medium. <br /> Beacon installation and sampling procedures are as follows and are provided in Appendix C. <br /> 1. Use a roto-hammer or other hammer drill to advance a 1 %-inch diameter hole first through <br /> asphalt. Upon drilling through asphalt use a push rod to clear for utilities within the 1%-inch <br /> hole to a depth of 3 feet bgs. <br /> 2. Advance the roto-hammer to a depth of three feet using a %-inch diameter drill bit. For <br /> locations that are through asphalt/concrete surfacing, the upper 12 inches of the hole is <br /> sleeved with a pre-cleaned metal pipe provided in the kit. <br /> 3. Install the Beacon Sampler,following manufactures direction, in the upper portion of the hole. <br /> Once the sampler is properly installed,the top of the hole is sealed with an aluminum foil plug <br /> and covered with soil for locations through asphalt/concrete surfacing. <br /> FINAL RIPON PCE INVESTIGATION WORK PLAN.DOCX 4-2 PROJECT NO.631021512 <br />