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Phase 11 Subsurface Investigation <br /> Tracy Corners Shopping Center <br /> 3225 North Tracy Boulevard <br /> Tracy,California 95376 <br /> Partner Project Number P14-129814.2 <br /> December 19,2014 <br /> Page 15 <br /> and vinyl chloride in accordance with United States Environmental Protection Agency (EPA) Method 70- <br /> 15. <br /> Pertinent Regulatory Agency Guidance <br /> The regulatory guidance used by Partner as part of the Phase II Subsurface Investigation is presented <br /> below. <br /> United States Environmental Protection Agency Regional Screening Levels and Department of Toxic <br /> Substances Control Attenuation Factor <br /> The May 2014 USEPA Regional Screening Levels (RSLs) are generic, risk-based chemical concentrations <br /> developed by the EPA Region 9 for use in initial screening-level evaluations. RSLs combine human health <br /> toxicity values with standard exposure factors to estimate contaminant concentrations that are considered <br /> to be health protective of human exposures over a lifetime through direct-contact exposure pathways <br /> (e.g.,via inhalation and/or ingestion of and/or dermal contact with impacted soil and/or indoor air). RSLs <br /> are not legally enforceable standards, but rather are considered guidelines to evaluate if potential risks <br /> associated with encountered chemical impacts may warrant further evaluation. <br /> While soil gas detections are not immediately comparable to the indoor air quality guidelines within the <br /> RSLs, the Department of Toxic Substances Control (DTSC) issued a building foundation default <br /> attenuation factor of 0.05 (sub-slab sampling locations) for sites where the attenuation factor in the <br /> October 2011 document Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to <br /> Indoor Air for an existing commercial building slab is unknown or cannot be directly measured. With the <br /> subsurface constituent concentrations and default attenuation factors, the associated theoretical PCE <br /> concentrations in indoor air can be calculated and compared to the DTSC's July 14, 2014 alternative air <br /> screening levels currently recommended in lieu of the RSLs. Theoretical TCE concentrations were <br /> compared to the 2014 EPA RSL. <br /> Laboratory Analysis Results <br /> SunStar reported the laboratory analysis results on December 16, 2014. Please see Table 2 for a summary <br /> of the sub slab soil gas sample CVOCs laboratory analysis results. <br /> Please see Appendix A for the full laboratory analysis report, which includes chain-of-custody and <br /> laboratory quality assurance/quality control (QA/QC) documentation. Laboratory QA/QC data were within <br /> acceptable limits. <br /> Sub Slab Soil Gas Sample Analytical Results <br /> The four sub-slab soil gas samples (SGl through SG4) and the duplicate sample (SVG1-DUP) contained <br /> detectable concentrations of PCE. The greatest concentration of PCE was detected in sample SG2 at 3,300 <br /> micrograms per cubic meter (pg/m3). Two samples, SG2 and SGl-Dup also contained TCE at 350 pg/m3 <br /> and 55 pg/m3,respectively. <br /> None of the soil gas sub-slab samples contained detectable concentrations above the laboratory <br /> reporting limits for cis-1,2 DCE, trans-1,2 DCE, and vinyl chloride. EPA Method TO-14 was used for <br /> PARTNER <br />