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1 <br />Consent Decree Exhibit C <br />3.0 Cleanup Standards and Nature and Extent of Contamination <br />Applicable or relevant and appropriate requirements (ARARs), cleanup standards and a <br />summary of the nature and extent of contamination for each environmental exposure pathway <br />are described in the following sections. <br />3.1 GAS EXPOSURE PATHWAY <br />3.1.1 Gas ARARs <br />Potential ARARs for the Everett Landfill/Tire Fire Site are described in attachment CAP-1. <br />ARARs specific to the landfill gas exposure pathway are summarized below. <br />• MTCA regulations indicate that the "solid waste closure requirements of Ch. 173-304 <br />WAC" shall be minimum requirements for cleanup actions for solid waste landfill <br />cleanups [WAC 173-340-710(6)(c)]. Closure standards are found in Section 173- <br />304-407, General closure and post -closure requirements. Ecology has determined <br />that requirements of WAC 173-304-460 (3)(e) and (f) are relevant and appropriate for <br />gas management. <br />• When monitoring during the post -closure period, the minimum functional standards <br />for performance for air quality and toxic air emissions of WAC 173-304-460(2)(b) are <br />appropriate. Ecology and the City have agreed that 100 ppm by volume of <br />hydrocarbons, expressed as methane, is an appropriate action level for publicly <br />accessible structures built on the landfill that are not associated with solid waste <br />handling and disposal. <br />• MTCA requires that best available control technologies (BACT), consistent with the <br />requirements of Chapter 70.94 RCW, be applied to releases of hazardous <br />substances to the air resulting from cleanup actions at the Site [WAC 173-340- <br />710(6)(b)]. <br />• The Puget Sound Clean Air Agency's (PSCAA) Regulation III focuses on toxic air <br />pollutants including those emitted by landfills. Regulation III requires new sources, <br />and in some cases existing sources, to demonstrate that emissions from the source <br />do not cause or contribute concentrations of toxic air pollutants at levels that could <br />pose a threat to human health or welfare. PSCAA uses Acceptable Source Impact <br />Levels (ASILs) for specific air toxics, which are provided in the regulations as <br />screening tools for identifying those cases that deserve more scrutiny. <br />3.1.2 Gas Cleanup Standards <br />Cleanup levels for ambient air concentrations of landfill gas pollutants are established using <br />Method B [WAC 173-340-750(3)]. Method B is used to calculate proposed cleanup levels <br />except as noted below. <br />Background concentrations are used as cleanup levels for the pollutants where background <br />information is available and it exceeds the cleanup standard calculated by Method B. Values for <br />FINAL March 2001 3-1 Everett Landfill Tire Fire Site <br />Cleanup Action Plan <br />