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4.0 DATA ANALYSIS
<br /> 4.1 Laboratory Analysis
<br /> Partner collected 21 soil samples, two groundwater samples, 10 soil gas samples, and five air samples on
<br /> July 6 and 7, 2023, which were transported in an iced cooler (soil and groundwater samples) or at ambient
<br /> temperature (soil gas and air samples) under chain-of-custody protocol to SunStar for analysis. Based on
<br /> field-screening results, visual observations, and/or olfactory observations, one soil sample per boring (four
<br /> soil samples total) and each groundwater sample(two groundwater samples total)was analyzed for PCE via
<br /> EPA Method 8260B. Each soil gas sample (10 soil gas samples total) was analyzed for PCE via EPA Method
<br /> TO-15. Each air sample (five air samples total) was analyzed for PCE via EPA Method TO-15 Selective Ion
<br /> Monitoring (SIM) Method (ultra-trace detection limit). The remaining soil samples were placed on hold at
<br /> the laboratory.
<br /> Cumulative laboratory analytical results are included in Appendix E and discussed below.
<br /> 4.2 Regulatory Agency Comparison Criteria
<br /> The San Francisco Bay RWQCB has established Environmental Screening Levels (ESLs) as an initial screening
<br /> level evaluation. ESLs aid in assessing the potential threats to human health, terrestrial/aquatic habitats,
<br /> and/or drinking water resources due to contaminants in soil, soil gas, and/or groundwater. Under most
<br /> circumstances, the presence of contamination below applicable ESLs can be assumed to not pose a
<br /> significant, chronic(i.e., long-term) adverse risk to the applicable receptor of concern. Conversely, sites that
<br /> exceed ESLs generally require further evaluation and/or remediation. Please note that the ESLs were
<br /> developed using default assumptions (e.g., standard exposure factors) and, consequently, are only meant
<br /> for screening level assessments. The ESLs should not be considered enforceable regulatory standards.
<br /> Cleanup levels ultimately dependent on site-specific factors and are established by the regulatory agencies
<br /> on a case-by-case basis.
<br /> 4.3 Soil Sample Data Analysis
<br /> PCE was detected in one of the analyzed soil samples (133-2) at a concentration above the laboratory
<br /> reporting limit (RL); however, this detection does not exceed the commercial/industrial ESL. None of the
<br /> remaining analyzed soil samples contained detectable concentrations of PCE above laboratory RLs and the
<br /> RLs do not exceed the commercial/industrial ESL.
<br /> Refer to Table 2 a summary of the soil sample PCE laboratory analysis results.
<br /> 4.4 Groundwater Sample Data Analysis
<br /> None of the analyzed groundwater samples contained detectable concentrations of PCE above laboratory
<br /> RLs and the RLs do not exceed the commercial/industrial ESL.
<br /> 4.5 Soil Gas Sample Data Analysis
<br /> PCE was detected in each of the analyzed soil gas samples at concentrations above the laboratory RLs. More
<br /> specifically, PCE was detected in soil gas samples 131-SG5, 131-SG15, B2-SG5, B2-SG15, B3-SG5, B3-SG15,
<br /> B4-SG5, B4-SG15, SS-5, and SS-6 at concentrations of 250, 260, 7,000, 3,600, 3,900, 3,100, 5,400, 2,100, 380,
<br /> and 270 micrograms per cubic meter(pg/m3), which exceed the commercial/industrial ESL of 67 pg/m3.
<br /> Additional Subsurface Investigation Report PARTNER
<br /> Project No.23-400162.14
<br /> July 31,2023
<br /> Page 9
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