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1 <br />Consent Decree Exhibit C <br />Ci <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />F11, <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />6.0 Future Conditions: Proposed Cleanup Actions <br />The proposed cleanup actions for potential future developed conditions consists of the following <br />components, organized by pathway: <br />Landfill Gas Pathway: <br />• Codes, covenants, and restrictions incorporating the requirements of the preferred <br />alternative for future development. <br />Compliance monitoring for buildings, pavement, open space, and undeveloped <br />areas. Buildings would include continuous monitoring systems for all ground floor <br />rooms that would automatically notify qualified landfill gas control system operations <br />and maintenance personnel and activate increased interior HVAC system ventilation <br />if flammable gas was detected at 1,000 ppm within the building. If flammable gas <br />concentration reached 10,000 ppm, or 20% of the lower explosive limit, alarms would <br />be activated that would cause the building to be evacuated. Additionally, buildings <br />and exterior areas will be monitored with hand-held instruments every two weeks <br />after the building and/or exterior area is opened for public access. If results do not <br />show an air quality concern for three months, monitoring will be performed quarterly. <br />Any result exceeding 100 ppm inside buildings or 500 ppm for exterior areas would <br />be subject to corrective contingency measures. <br />An active landfill gas control system will be installed with development phases. It will <br />collect landfill gas from beneath buildings, pavement and open spaces associated <br />with developed portions of the Site. See Figures 6-1 and 6-2 for conceptual cross <br />section and plan view of the phased active landfill gas control system. This phased <br />active vacuum extraction system consists of perforated pipes running generally east - <br />west on minimum 100-foot centers buried in gravel above the landfilled materials. <br />The perforated pipes are connected to a header system that directs collected gas to <br />one or more vacuum blowers and discharge points. PSCAA will be consulted for any <br />future discharge of landfill gas. Discharge could be treated (biofilter, carbon filter <br />canister, flare) or untreated. If untreated, and modeling of the discharge <br />demonstrates the discharge would not cause exceedance of ASIL standards, <br />PSCAA permitting would not be necessary. If treatment is proposed, PSCAA <br />permitting and approvals will be required. Modeling of both treated and untreated <br />conditions has demonstrated that various discharge scenarios are able to meet <br />MTCA cleanup levels and ASIL standards. <br />• Confirmational modeling at landfill gas discharge points would also be completed to <br />confirm that constituents of gas emitted from constructed discharge locations are <br />consistent with the assumptions of landfill gas pollutant concentrations and landfill <br />gas flow used in the modeling to design the gas control systems. <br />Buildings will be protected by a geomembrane beneath the foundation slab that will <br />be booted and sealed around piles and utility penetrations as appropriate. A full-time <br />continuous ground floor monitoring system will automatically activate installed HVAC <br />systems and centralized alarms if flammable gas concentration exceeds 1,000 ppm. <br />Temporary enclosures erected over pavement or open space areas will contain <br />continuous monitors that would activate an alarm if triggered. <br />FINAL - March 2001 <br />6-1 Everett Landfill Tire Fire Site <br />Cleanup Action Plan <br />1 <br />