ARCHIVED REPORTS_REMOVAL ACTION COMPLETION REPORT

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DRAFT REMOVAL ACTION COMPLETION REPORT SOUTHERN PORTION OF NEIGHBORHOOD C MOUNTAIN HOUSE,SAN JOAQUIN COUNTY,CALIFORNIA EXECUTIVE SUMMARY This Removal Action Completion Report(RACR) has been prepared by Condor Earth Technologies, Inc. (Condor) for the southern portion of Neighborhood C (Site), located in the new community of Mountain House, California (Figures 1 through 4, Appendix A). The Site includes the western side (southbound lanes) of Great Valley Parkway. This RACR describes remediation of surface soil containing residual dieldrin concentrations from historic agricultural practices at the Site. This RACR has been prepared pursuant to a Voluntary Cleanup Agreement between Mountain House Developers, LLC (MHD), and the California Environmental Protection Agency (Cal/EPA) Department of Toxic Substances Control (DTSC). The removal action was completed in general accordance with the DTSC approved Removal Action Workplan(RAW),dated July 9,2007. The area of concern included approximately 40.6 acres of the 61-acre agricultural property comprising the southwestern portion of Neighborhood C. Analytical results from various environmental investigations indicated that the organochlorine pesticide(OCP)dieldrin was the sole constituent of concern for the Site. Dieldrin concentrations in surface soil were higher than regulatory screening levels for residential land use,and a removal action was therefore warranted. The selected remedy was surface soil excavation of approximately 40.6 acres to a depth of 0.5 feet below ground surface (bgs) using paddle-wheel type scrapers. The total in-place volume of soil proposed for removal was approximately 33,000 in-place cubic yards (yds3). The actual volume of soil removed was approximately 70,000 in-place yds3 due to additional excavation that was required in order to meet the cleanup goal. Excavated soil was encapsulated beneath Great Valley Parkway in areas without planned subsurface utilities. The cleanup goal for the Site is the California Human Health Screening Level(CHHSL) for sensitive land use for dieldrin: 0.035 milligrams per kilogram (mg/kg). Seven years after the RAW was approved and owners were ready to implement the RAW,the implementation of the RAW was combined with the mass grading plan for the entire area of Neighborhood C. Dieldrin removal and air monitoring operations began on October 18, 2013. Once the initial 0.5 feet of surface soil had been removed, one confirmation sample per one-acre subparcel was collected and analyzed for dieldrin. Most of the subparcels did not meet the cleanup goal and additional excavation was required. Additional iterations of excavation and confirmation sampling proceeded until the cleanup goal was achieved on all subparcels. During movement of dieldrin-containing soil, air monitoring was conducted by monitoring real-time dust concentrations and air sampling for dieldrin at the fencelines. No dieldrin was detected in air samples during the soil removal, and the dust control plan was successfully implemented. Waste characterization results for the entombment area beneath Great Valley Parkway indicate dieldrin concentrations are above the action level of 0.035 mg/kg for administrative controls specified in the RAW. Waste soil encapsulation beneath Great Valley Parkway is protective of human health and the environment based on engineering and future administrative controls. Engineering controls include a cap of non-contaminated fill soil and pavement of the roadway. Conservatively, SHM implemented an additional engineering control that was not originally included in the RAW: an orange warning fabric was i