Methane mitigation is one of the biggest challenges when it comes to the redevelopment of closed landfills, coastal infill, wetlands, and natural geologic formations.
Methane gas is lighter than air, flammable, and, if allowed to accumulate in enclosed spaces, can present an explosion hazard. Therefore, an engineered methane mitigation system (MMS) is essential to the design and safety of structures built on top of subsurface methane sources. There are many guidance documents from various state and federal authorities for the design of vapor intrusion mitigation systems. However, these are typically tailored to volatile organic compound vapors, which have different physical and migration characteristics than methane. In addition, state or county ordinances or regulations may impose specific requirements regarding the closure and post-closure development of landfills or geological deposits of petroleum hydrocarbons near the ground surface that generate significant quantities of methane. A nuanced understanding of the different characteristics between vapors and gases (e.g., methane) is pivotal to a successful MMS design. Especially if a municipal solid waste landfill site is found to also contain deposits of liquid or solid hazardous waste, as this combination presents both an explosive gas hazard and a toxic vapor risk.
“It’s crucial to address methane issues during land redevelopment to avoid turning a lucrative investment into a colossal challenge,” said Sigrida Reinis, PhD, PE, Senior Associate, Langan. “Our team navigates these complex projects from start to finish, implementing mitigation systems to save clients time and money, whether the methane originated from landfills, earthquake fill, historic wetlands, oil and gas systems, or elsewhere.”
Methane is also a potent greenhouse gas and may require air district permitting or system exhaust treatment depending on local regulations. In contrast, if methane generation rates are high enough, it may be possible to capture and use the methane for on-site power generation. An experienced environmental team can review site histories, current environmental conditions, and the proposed site use to determine regulations that may apply to the design, installation, and monitoring of the MMS.
Sigrida Reinis, PhD, PE has 25 years of experience in environmental engineering and construction management, specializing in complex remediation projects, including commercial and residential redevelopment. Reinis has designed vapor mitigation systems for properties to be built on closed landfills and brownfield sites, as well as existing buildings undergoing remediation.
Jessica Schaettle, EIT is a Project Engineer with seven years of experience working on environmental projects across California. She specializes in vapor intrusion assessments and vapor and methane mitigation systems design for projects including developments on closed landfills. Schaettle is also experienced in environmental litigation and remediation projects.