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INSTRUCTORS:
Timothy D. Stark, P.E.

Sponsored by ASCE's Geo-Institute and ASCE Continuing Education.

Purpose and Background

Subsurface heating events are described by many terms, such as subsurface fires, pyrolysis, combustion, rapid oxidation, smoldering, and metallic reaction. These hazards can be experienced at Subtitle D, construction demolition and debris (CD&D), and industrial waste landfills. Subsurface heating events are prevalent worldwide, including United States, Canada, Sweden, Finland, France, United Kingdom, Jordan, Greece, Philippines, Indonesia, and Israel. Current studies indicate that remedial expenditures can be significant and exceed 100 million USD.

In the United States, FEMA (2002) estimates that 8,400 heating events occur at Subtitle D (municipal solid waste; MSW) landfill facilities every year. The number of heating events is likely higher because they may be undetected hot spots at sites because of infrequent monitoring and no or limited visible effects. Although the majority of the heating events are relatively small and contained or suppressed at the working face by landfill personnel, large events (10-30/year) can occur and require specialized response, expertise, and additional environmental oversight. These heating events are problematic for Subtitle D landfills because they are challenging to identify and delineate, can remain undetected for a relatively long period of time, are difficult to extinguish, may damage engineered components, and produce side effects that may damage a facility enough to warrant permanent closure. In addition, these subsurface heating event’s direction and rate of movement is not uniform or constant due to MSW heterogeneity, location and operation of landfill gas wells, and inadvertent thermal barriers (e.g. a landfill haul road or thick layer of waste cover soils). As a result, this webinar presents landfill indicators and changes in these indicators for detecting and delineating heating events and identifying the direction and rate of movement. Trend analysis techniques for analyzing changes in landfill gas, temperatures, leachate, and settlement are presented for use as an effective technique for identifying this hazard at an early stage. This webinar also describes how to assess performance of engineered components (e.g. service life of HDPE geomembranes) and present methods to isolate and contain heating events.

Subsurface heating events in landfills – portrayed through social media and news outlets – have caused the public to become more aware of the environmental and health risks. As a result, this webinar provides guidance for rapid investigation after the development of a subsurface heating event to evaluate, locate, delineate, contain, and possibly suppress the heating event to protect human health, safety, and the environment.

Learning Objectives

• Understand the causes and mechanisms for elevated temperatures in landfills
• Learn about technologies and methods to detect subsurface heating events
• Learn how to identify the direction and rate of movement of elevated temperatures
• Understand geotechnical stability, settlement, and response of landfills
• Understand the impact to engineered components such as composite liner system, leachate collection, final cover, and gas extraction systems
• Learn design methods for isolation and containment barriers