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past the monitoring ports." Parametrix (1998c) provides a status of <br />sinkhole monitoring (including thermocouple temperature probes) and a <br />map showing seven sinkhole locations where water injection probes were <br />installed to help extinguish subsurface fires associated with sinkhole <br />subsidence. Thermocouple temperatures over 1,000 °F were observed, <br />indicating active combustion. Liner repairs at sinkhole locations were also <br />proposed. <br />Due to failure of water injection at sinkholes to prevent continued <br />subsurface fires, the County of Hawaii contracted Walker Consultants, <br />Inc., to attempt alternative mitigation techniques. Walker recommended <br />injection of water and liquid carbon dioxide to quench fires, and sealing of <br />liner leaks with wetted soil. In December 2001, 24 carbon dioxide (CO2) <br />injection probes and 58 eater injection probes were installed. In June <br />2003,18 addition CO2 probes were installed. Water and CO2 were injected <br />episodically from January 2002 through at least January 2004 (Walker <br />2004). Walker describes "areas of concern" as having methane (CH4) <br />levels greater than 5 percent and oxygen (02) levels greater than 4 percent, <br />and therefore prone to combustion. Walker (2004) describes a general <br />decrease in the extent of "areas of concern" following water/CO2 <br />injection. The geographic areas of highest concern were the east -center, <br />north -center and northwest portion of the landfill (Walker, 2004). <br />1.2 PROBLEM DEFINITION <br />ERM understands that the Kailua-Kona Landfill continues to support <br />subsurface waste combustion, with potential associated air emissions of <br />combustion gases (along with decomposition by-products). A <br />Supplemental Environmental Project (SEP) is proposed to achieve the <br />following principal objectives: <br />1) Better understand the nature and extent of subsurface fires and <br />associated gas by-products to facilitate development of effective <br />mitigation strategies; <br />2) Conduct a demonstration of subsurface landfill fire suppression using <br />a fire -retardant foam; <br />3) Extinguish a known area of burning waste material and improve <br />subsurface conditions at the landfill; and <br />4) Develop a plan and cost estimate for extinguishing all existing landfill <br />fires. <br />ERM 3 KAILUA-KONA LANDFILL/ 0061204 - 3/14/2008 <br />