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Draft Environmental Impact Report Page IV.E-4 I' p g Forward Inc. Landfill Expansion Project re-location, and associated site modifications necessitated by the expansion. The proposed expansion includes an increase in the number of allowable daily load deliveries to the landfill. The objective is to evaluated potential health risks that may occur as-a result of the proposed landfill expansion. The SCS (2008)risk assessment has been peer-reviewed by Stellar Environmental Solutions, Inc. prior to incorporation into this EIR. While there are no definitive nrtive standards for risk assessments specified by CEQA, all quantitative risk assessments are typically performed based in large part under standard guidelines set forth ' by the USEPA. Deviations from USEPA standards are outlined by state regulatory agencies such as the Cal/EPA. Evaluation of health risks in the SCS (2008) report is considered consistent with standard regulatory guidelines and risk assessment practice. The EPA has historically defined acceptable risk in a conservative manner for superfund sites as health risk from 30 year (residential) exposures that do not result an increase in cancer of reater than 1 in 1,000,000. The EPS target risk range is from 1 in 10,000 to 1 in 1,000,000 (1 x 10 to 1 x 10-6). Acceptable risks by the RWQCB (inherent for example.in their environmental screening levels) F generally fall within the range of between 1 in 100,000 to 1 in 1,000,000 (10-5 and 10-, respectively). The chronic non-carcinogenic risks in the Risk Assessment (SCS,2008)are presented as the ratio of the CDI to the RfD (CDL•RfD) resulting in a number called the Hazard Quotient(HQ). In addition,the acute risks for residential receptors were presented as the ratio of the receptor `i concentration or EPC to the Reference Exposure Levels (RELs) (EPC:REL). The sum of all of the CDI/RFD or EPC/REL ratios (i.e., HQs) of chemicals under consideration is called the Hazard Index.(HI). If the CDI or EPC is smaller than the RfD or REL, the HQ will be less than 1.0. If the CDI or EPC is larger than the RfD or REL,the HQ will be greater than 1.0. An HQ less than 1.0 3 .F indicates that there is not likely to be any adverse health effects from the exposure. An HQ greater than 1.0 indicates that there is a potential health hazard for the exposed population. When a human population is exposed to several chemicals contaminants, such as with the Project, HQs for each of the contaminants are added together to produce the HI. As with the HQs, an HI less than 1.0 indicates that there is not likely to be any adverse health effects from the exposure while an HI greater than 1.0 indicates that there is a potential health hazard. The SJVAPCD CEQA guidelines have an HI threshold of significance of 1.0. This HI threshold of 1.0 was used as the CEQA significance level for evaluating the proposed Project scenarios. ra> To determine the lifetime cancer risk for a particular chemical contaminant, CSFs are multiplied }' by the CDI of the contaminant under consideration. The total lifetime cancer risk for a site is determined by summing all the individualized cancer risks for the various chemicals of concern. Chronic non-carcinogenic and carcinogenic risks are based on the average COPC emissions from the worst-case 30 years of emission levels. The 30-year average values were considered 1 appropriate for calculating long-term human health risks,which are generally based on 30 years of exposure rather than short-term exposure levels. The report focuses on quantifying potential health risks associated with off-site residents and off-site workers resulting from chemical emissions from the proposed landfill modifications. Specific off-site receptors evaluated include six residences, the Northern California Youth i Center, and the Northern California Women's Facility, all of which are located within a mile of the site. The HRA also evaluates potential exposures to on-site landfill workers through a screening with respect to applicable occupational hazards. Risks to the above receptors were "a estimated under both existing and proposed future expansion scenarios. The primary transport