Stability Analysis for a Landfill Experiencing Elevated Temperatures

Abstract

This paper describes input parameters and stability analyses for a municipal solid waste (MSW) landfill experiencing elevated temperatures due to an aluminum waste reaction. The scenarios analyzed to investigate slope stability include elevated temperatures and increased gas and liquid pressures. The input parameters are discussed including strength parameters for MSW before and after being impacted by elevated temperatures, inclusion of gas pressures, and possible leachate levels. The MSW that was thermally degraded at this site was modeled using an effective stress cohesion and friction angle of zero and 20 degrees, respectively. INTRODUCTION Aluminum production wastes can be disposed of in MSW landfills because this waste is not categorized as hazardous under 40 CFR §§ 261, subpart D which explicitly lists the materials that are defined as hazardous. Aluminum waste products, e.g., dross, salt cake, baghouse fines, etc., are not listed under 40 CFR §§ 261, subpart D so are not a hazardous waste under this code section. Under 40 CFR §§ 261, subpart C, if a waste exhibits one of the following four characteristics of a hazardous waste, i.e., ignitability, corrosivity, reactivity, or toxicity, the waste is categorized as hazardous and cannot be disposed of in an MSW landfill. Calder and Stark (2009) recommend new testing protocol that may result in aluminum wastes being classified as “reactive” or even “ignitable”. Aluminum waste is usually in the form of what the industry calls aluminum dross or baghouse fines (BHF). The aluminum production waste usually contains metallic aluminum, aluminum oxides, salts, and aluminum carbides, and nitrides (Hwang et al. 2006). Generally, disposal of these wastes has not been problematic, but incidents of reaction, combustion, and/or pyrolysis from these materials upon contact with liquid within landfills have been reported (USEPA 1994). Such a situation can develop when aluminum wastes have been previously deposited and then leachate recirculation is initiated in areas of the aluminum waste. Thus, initiation of leachate recirculation in an existing landfill should be carefully considered before initiation. Hazardous and potentially explosive gases, including hydrogen, methane, acetylene and ammonia can be generated via the highly exothermic reaction with metallic aluminum, aluminum carbides, and aluminum