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Quality Cleaners VOCs Based on existing data,the PCE release mechanism appears to have been poor housekeeping from within the dry cleaning suite. The primary source of COPC, primarily PCE, was the dry cleaning solvent that was used at the dry cleaners until circa 2007. A secondary source is residual PCE and TCE in soil gas beneath the dry cleaner suite and PCE in groundwater beneath and adjacent to the dry cleaner suite. Sewer laterals and pipelines are common release mechanisms for PCE from dry cleaners. The assessment of the sewer lateral connected to the Quality Cleaners has yet to be conducted. Petroleum Hydrocarbons and Related COPC The release mechanism related to the TPH and related PAHs, PCBs, and LUFT Metals may have been associated with ASTs, poor material handling procedures, or, reportedly, from a dry well and/or leach field. Information from within the EHD records suggests at least several truckloads of soil were excavated and transported offsite, hence, it is possible the primary source of the petroleum hydrocarbons has undergone potentially significant removal. Secondary sources, including residue in groundwater, are currently unknown. Organochlorine Pesticides The potential release mechanism related to OCPs may have been primarily associated with the possible storage or mixing at areas on the Site where barns or outbuildings were formerly located. 5.0 PROPOSED APPROACH TO SITE CHARACTERIZATION The proposed approach and sequencing of sampling tasks are described below. The details related to technical methodologies are described in Section 6.0-Scope of Work and in the SAP. Vapor Intrusion Assessment of Selected Tenant Suites Given the presence of PCE and TCE in sub-slab soil gas and the transient nature of soil gas in the environment, the initial task will be to collect three sub-slab soil gas samples beneath the Quality Cleaners to confirm the detections related to the sub-slab soil gas samples collected in December 2014. A single five-foot deep soil gas probe will be installed beneath the dry cleaners suite to assess the vertical extent and attenuation of PCE and TCE in soil gas. This work will be preceded by a conduit survey,assessing indoor air with an organic vapor meter,and performing an inventory of materials within the three tenant spaces to assess whether any materials containing VOCs are present. Indoor air samples will be collected from the Quality Cleaners and the adjacent Comcast and Fred Loya tenant suites; three outdoor ambient air samples will be collected during this task. This work will be performed to assess for the potential vapor intrusion into these suites and to assess potential inhalation exposures to commercial workers in these tenant spaces. Sampling and Analysis Workplan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 18