Application of tire chips to reduce the temperature of secondary geomembranes in municipal solid waste landfills Azadeh Hoor, R. Kerry Rowe ⇑ GeoEngineering Centre at Queen’s-RMC, Department of Civil Engineering, Queen’s University, Kingston, Ontario, Canada K7L 3N6 article info Article history: Received 20 June 2011 Accepted 21 December 2011 Available online 4 February 2012 Keywords: Landfill Geomembrane Secondary liner Tire chip Temperature Service-life abstract Heat generated by the biodegradation of waste and other chemical processes in a landfill can potentially affect the long-term performance of landfill liner system, in particular that of a high-density polyethylene geomembrane. In a double liner system, the difference in leachate exposure and temperature might improve the long-term performance of the secondary geomembrane compared to that of the primary geomembrane. However, in some cases, the temperature is likely to be high enough to substantially reduce the service-life of the secondary geomembrane. This study explores the possible effectiveness of using tire chips as thermal insulation between primary and secondary liners to reduce the temperature of secondary geomembranes as compared to traditional soil materials. Heat and contaminant migration analyses are performed for cases with no insulation and for cases in which a layer of soil or tire chips has been used as thermal insulation between the primary and secondary liners. The effect of insulation on prolonging the service-life of a secondary geomembrane and, consequently, on contaminant transport through a liner system is examined for the case of a volatile organic compound (dichloromethane) found in landfill leachate. The study suggests that the use of tire chips warrants consideration, however there are other practical issues that require consideration in the detailed design and construction of landfill lin- ers. Issues such as finite service-life, low working temperature, excessive settlement, ability to generate internal heat, leaching of tire chips and limitations in performing electrical resistivity leak detection tests are identified. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction To provide environmental protection, modern landfills are ex- pected to prevent contaminant migration to soil and groundwater for what is called the contaminating lifespan of a landfill (for large modern landfills this could be hundreds of years, Rowe et al., 2004). Composite liners, involving a geomembrane (GMB) over a geosynthetic clay liner (GCL) have gained widespread acceptance for use in landfill barrier systems (Rowe et al., 2004). However, to ensure long-term environmental protection is achieved, it is necessary to minimize the factors that affect leakage through com- posite liners and the long-term performance of GMBs and GCLs. Elevated liner temperature is one important factor that affects long-term performance of liners components. The biodegradation of waste, the heat produced by the hydra- tion of incinerated ash and the disposal of reactive waste are the primary factors contributing to heat generation in a landfill and, consequently, to the increase in liner temperature. Landfill moni- toring has shown that the temperature on a landfill liner may reach 30–40 °C for a typical municipal solid waste landfill and potentially up to 60 °C for a moisture-augmented landfill (Rowe and Hoor, 2009; Rowe and Islam, 2009). Also, reactive wastes such as alumi- num production wastes have been observed to produce tempera- tures in the landfill waste greater than 100 °C, but no liner temperature has been reported (Calder and Stark, 2010; Martin et al., 2011). High temperature increases the hydraulic conductivity of clay liners and the diffusion coefficient for the geomembrane and clay liners in a barrier system (Collins, 1993; Rowe, 1998; Rowe and Arnepalli, 2008). It also accelerates the aging of GMBs (Hsuan and Koerner, 1998; Rowe, 1998, 2005; Rowe and Rimal, 2008a,b; Rowe et al., 2009) and it may result in the desiccation of clay com- ponents (Rowe, 2005; Southen and Rowe, 2005a,b). In a double-lined landfill, both primary and secondary liners may be affected by high temperatures (Rowe and Hoor, 2009). Pre- vious studies predicted the temperature and the service-life of pri- mary GMBs. However, until the recent work by Rowe and Hoor (2009), no one had studied the service-life of secondary GMBs. On- tario Regulations 232/98 under the Ontario Environmental Protec- tion Act, requires that the service-life of secondary GMBs exceed 350 years (MoE, 1998). Yet, the work by Rowe and Hoor (2009) showed that, in some cases, the temperature of secondary GMBs 0956-053X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2011.12.026 ⇑ Corresponding author. Tel.: +1 613 533 3113; fax: +1 613 533 2128. E-mail addresses: Azadeh.Hoor@genesisoilandgas.com, a.hoor@ce.queensu.ca (A. Hoor), kerry@civil.queensu.ca (R.K. Rowe). Waste Management 32 (2012) 901–911 Contents lists available at SciVerse ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman