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41011110 awn Munger, CHG <br />If you have any questions regarding this report, please contact us. <br />Sincerely, <br />ENGEO Incorpo ated <br />ofi onner <br />12066.002.000 <br />San Joaquin County Environmental Health Department <br />November 30, 2018 <br />Mountain House Neighborhood A, Units 3 and 4 <br /> <br />Revised January 22, 2019 <br />SOIL GAS CHARACTERIZATION REPORT <br /> <br />Page 4 <br />Table A provides a summary of the sample concentrations and corresponding screening levels <br />for residential soil. <br />January 10, 2019 Sampling Event <br />The three soil gas samples reported detectable concentrations of TPH-gasoline, ranging from <br />282 micrograms per cubic meter (ug/m3) to 4460 ug/m3 (SG-5). The concentrations are below <br />applicable RWQCB Tier 1 Environmental Screening Levels (ESLs). <br />Several VOCs were reported for the three samples, the following are the maximum concentrations <br />observed for these analytes: Acetone (170 ug/m3), Carbon Disulfide (20 ug/m3), Benzene <br />(48 ug/m3), Toluene (330 ug/m3), 4-Methyl-2-Pentanone (MIBK) (5.8 ug/m3), Xylenes (111 ug/m3), <br />Styrene (4.8 ug/m3), Hexane (57 ug/m3), 2-Hexanone (3.2 ug/m3), tert-Butanol (9.4 ug/m3 ). The <br />reported concentrations do not exceed the applicable RWQCB Tier 1 ESLs, DTSC Modified <br />Screening Levels, or USEPA RSLs. <br />Table A provides a summary of the sample concentrations and corresponding screening levels <br />for residential soil. <br />Quality Control/Data Validation <br />The leak check compound 2-propanol was not reported for the January 2019 samples. Based on <br />DTSC guidelines this verifies the data is valid. <br />DISCUSSION AND CONCLUSION <br />Review of the laboratory test results found detectable concentrations of total petroleum <br />hydrocarbons (TPH) as gasoline and some detectable concentrations of volatile organic <br />compounds (VOCs); however, all of the reported concentrations were at, or below, the applicable <br />residential screening levels. <br />Given the distance from the sampling locations and graded residential lots (-150 feet), natural <br />attenuation and degradation would be expected both laterally and vertically. In addition, the <br />petroleum pipeline elevation is 6 to 8 feet above the residential lots. <br />Based on the findings of the soil gas assessment, no significant soil gas impacts are indicated <br />and the area is suitable for residential use. No further environmental investigations are <br />recommended at this time. <br />Attachments: Figures <br />Table A - Summary of Analytical Results <br />Appendix A - Laboratory Analysis Report, Torrent Laboratories Inc.