SU0007861 - Laserfiche WebLink

Home Browse Search

Draft Supplemental Environmental Impact Report Page IV.E-14 Forward Inc. Landfill 2014 Expansion Project As with the criteria pollutants (see the Air Quality Section), the project would increase toxic air contaminant emissions from LFG-derived sources with two options: additional LFG is controlled either by additional flare capacity (flare option) or LFG engines at a new LFG to energy facility (LFG engine option). Both of these options include the additional emissions from the Ameresco Inc. LFG to energy project that has recently been constructed. Air toxics within LFG typically consist of benzene, chloroform, methylene chloride, perchloroethylene, trichloroethylene,vinyl chloride, as well as other air toxics. Landfill gas emission estimates are based on EPA's Landfill Gas Emissions Model (LandGEM). Appendix G, Air Quality Impact Assessment, of the Final EIR includes a review of potential pathways for human exposure to toxics from the project. Some of the potential pathways have been excluded because the specifics of the project mean they would not be complete pathways for the purposed of the HRA. The pathways that were examined as part of the HRA included the inhalation of chemicals present in landfill gas (LFG) and emissions from vehicles, dermal adsorption, soil ingestion, home-grown produce, and mother's milk. As identified in Standards of Significance, the significance of air toxic emissions depends upon the chance of contracting cancer from exposure to air toxics, or upon having adverse health effects from exposure to non-carcinogenic air toxics. Cancer risks would be significant if the incremental risk equals or exceeds 10 in a million for the Maximally Exposed Individual.' Exposure to non-carcinogenic substances would be significant if the Hazard Index (HI) exceeds 1.0.8 The standards are typically applied to the results of a HRA through a detailed air dispersion modeling effort using the EPA's AERMOD dispersion model. This assessment is intended to provide a worst-case estimate of the increased exposure by employing a standard emission estimation program and an accepted pollutant dispersion model. Conservative health risk methodologies were used in the SCS Engineers health risk assessment in order to estimate maximum potential health risks. These methodologies are anticipated to overestimate both non carcinogenic and carcinogenic health risk, possibly by an order of magnitude or more. For carcinogenic risks, the actual probabilities of cancer formation in the populations of concern due to exposure to carcinogenic pollutants are likely to be lower than the risks derived using the risk assessment methodology. In accordance with OEHHA guidelines, the HRA was accomplished by applying the highest estimated concentrations of TAC at the receptors analyzed to the established cancer potency factors and acceptable reference concentrations for non-cancer health effects. The HRA for this project utilized the EPA approved AEROMOD model. AEROMOD is a refined air dispersion modeling program and can compute emission concentrations from many sources at many J locations based on actual meteorological data.The meteorological data used in this HRA was obtained from the SJVAPCD web site and had already been reviewed for use in AEROMOD. 7 The Maximally Exposed Individual represents the worst—case risk estimate,based on a theoretical person continuously exposed at the point of highest compound concentration in the air. The analysis used emission of LFG based on results from the EPA Landfill Gas Emissions Model(LandGEM)gas generation models. For the current permitted and future potential scenarios,the worst-case 30-year span was used;2012 through 2041 for current permitted,and 2022 through 2051 for future potential. 8 The Hazard Index is the ratio of a hazardous air pollutant concentration to its Reference Concentration,or safe exposure level. If this"hazard index"exceeds one,people are exposed to levels of hazardous air pollutants that may pose non—cancer health risks.