Laserfiche WebLink
F <br /> Y <br />+ an unacceptable health risk to current and future use of the Site (commercial-Industrial land- <br /> use), i 3 <br /> Tier 1 Groundwater <br /> The historic groundwater data, including those collected from each soil boring will be , <br /> compared to the CRWQB-SFBR Tier 1 ESLs for residential receptors for shallow soil levels i <br /> ,-(Table A). An evaluation will be made to determine if the resultant concentration will pose <br /> an unacceptable health risk to current and future use of the Site (commercial-industrial land- <br /> use) 1 <br /> 10.2.2 Tier 2 RBCA Analysis <br /> Based on current Site use, the exposure pathway for each giroup considered in this study <br /> will include the inhalation of indoor air (vapor intrusion) pathway. If comparative data <br /> exceed Tier 1 values, the Tier 2 risk assessment will be conducted. <br /> Tier 2 Exposure Assumptions <br /> The risk scenario will include a shallow surface (4.5 to 5.0 feet bgs, sample collected k <br /> beneath the surface outside M <br /> de the budding) evaluation for the applicable receptors <br /> (commercial and residential exposure). Soil vapor analyses will be evaluated under the Tier <br /> 2 scenario. <br /> Tier 2 Risk Evaluation <br /> CThe inhalation risk evaluation will be prepared pursuant to Department of Toxic Substances i <br /> Control (DTSC) guidance (Guidance for the Evaluation and Mitigation of Subsurface Vapor r <br /> Intrusion To Indoor Air, Interim Final, DTSC revised February 7, 2005). The guidance is <br /> designed to evaluate if subsurface conditions pose the potential for non-cancer hazard index <br /> and cancer risk for each receptor group from subsurface vapors to individually or <br /> cumulatively pose a significant risk or hazard. This can also be stated as to determine if <br /> cancer risks are less than one in one million (10-6) and all non-cancer hazard indices are <br /> less than 1.0. Should the results fall below each threshold, then it would suggest that the <br /> compounds detected in the soil gas beneath the surface do not pose an unacceptable risk to <br /> human health undercurrent conditions <br /> I <br /> I <br /> I <br /> r. <br /> F <br /> k <br /> F <br /> k <br /> Workplan to Conduct Subsurface Soil Vapor Intrusion Study <br /> ATC Project 54.26874.0001 ( \V/��TC <br /> Page 11 <br />