Abstract Description: Ground gas methane has emerged as a potential hazard for redevelopment project in recent years. Methane can be generated in the ground from various sources, including buried waste, petroleum releases, oil and gas wells, subsurface natural gas utilities, bioremediation activities, and decay of naturally occurring organic material. Various state agencies, including NCDEQ, CDPHE, MPCA, CA DTSC, OCFA, and LADBS, and technical authors (e.g. Eklund and Sepich) have identified this concern and subsequently developed guidance specifically for managing ground gas methane. While the spirit of these documents’ center on the protection of building occupants from explosion and asphyxiation risk from methane, these documents vary (sometimes significantly) in the approach to both the assessment and mitigation of ground gas methane. Variances include but are not limited to the number of sampling probes per square footage, maximum allowable pressure, maximum allowable methane concentration for development, thresholds for passive versus active systems, and post-mitigation monitoring frequency. The lack of consistency between guidance documents has created confusion for property developers with assets in multiple jurisdictions.
This presentation will provide a review and examination of how ground gas methane can be a concern at a site. Current methane guidance documents and white papers will be reviewed, and key similarities and differences related to methane assessment, conceptual site model development, approach to redevelopment, mitigation thresholds, and ongoing monitoring requirements will be provided for stakeholders involved in development projects.
