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Cleanup in Vulnerable Communities'Initiative Discovery Project Reference:Favorite Cleaners <br /> and Enforcement Discovery Investigation Work Plan Project Number:60688620 <br /> 7. Screening Risk Evaluations <br /> One specific objective of the Discovery Investigation is to estimate the potential threat to public health and/or the <br /> environment posed by the Subject Property and compare estimated risk/hazards among sites being evaluated. <br /> The human health screening evaluation will be performed in accordance with the protocols detailed in the <br /> Programmatic QAPP Section 7.1 "Human Health Screening Evaluation". In addition, project-specific guidance on the <br /> performance of the screening evaluation will be requested from the DTSC Project Manager and DTSC staff <br /> toxicologist. <br /> 7.1 Human Health Screening Risk Evaluation <br /> The first step of the human health risk evaluation will be to construct a CSM pertinent to potential vapor intrusion <br /> inhalation exposure for the property.A preliminary CSM for the human health vapor intrusion screening evaluation is <br /> presented in Figure 5. The CSM will identify the potential receptor groups, exposure media, and exposure pathways <br /> associated with the Subject Property. <br /> Chemicals of potential concern(COPCs)will then be identified.All organic chemicals detected in at least one sample <br /> will be included as COPCs.The maximum detected concentration of each COPC will be used as the exposure point <br /> concentration in the risk assessment. <br /> Land use will be considered residential in nature, unless otherwise specified. Soil vapor will be evaluated using <br /> Residential Risk Based Screening Levels(RBSLs). Indoor air within commercial buildings will be evaluated using <br /> commercial/industrial RBSLs. <br /> Default exposure parameters listed in DTSC's Human Health Risk Assessment(HRAA)Note 1 (DTSC 2019a)4, along <br /> with toxicity values listed in HHRA Note 10(DTSC 2019b), will be used to evaluate cancer risks and non-cancer <br /> hazards to current and potential future receptors at the Subject Property. For the screening level assessment,values <br /> listed in DTSC's HHRA Note 3(DTSC 2022b)will be used. In cases where screening levels are not listed in DTSC's <br /> HHRA Note 3, USEPA's Regional Screening Level (RSL)(USEPA 2023)5 will be used. Cumulative cancer risks and <br /> non-cancer hazards will be evaluated for receptors at the Subject Property, and a discussion of uncertainties in the <br /> risk evaluation will be presented in a separate section. <br /> The exposure pathway that likely will drive the D&E Discovery Investigation is inhalation of chemical vapors <br /> emanating into indoor air from subsurface sources(vapor intrusion). If VOCs are detected on-site in the subsurface <br /> and/or on-site or off-site in indoor air, an assessment of potential infiltration to indoor air will be conducted as per the <br /> Programmatic QAPP.A multiple-lines-of-evidence approach as described in the Vapor Intrusion Guidance may be <br /> adopted to refine the risk evaluation. Cumulative cancer risk and non-cancer hazard estimates may be used to <br /> determine whether additional investigations or remediation is needed at the Subject Property. <br /> 4 https://dtsc.ca.gov/wp-content/uploads/sites/31/2022/02/HHRA-Note-1-April-2019-21A.pdf <br /> 5 htti)s://www.epa.aov/risk/reciional-screeninci-levels-rsls-generic-tables <br /> Prepared for: California Department of Toxic Substances Control AECOM <br /> 33 <br />