A Practical Evaluation of Petrogenic and Biogenic Methane Sources in the Context of Redevelopment and Explosive Hazard Management in Los Angeles, California

In Southern California and in certain regions of the world where methane gas is prevalent due to petrogenic activity, careful planning is needed to manage the potential explosive hazard associated with methane encroachment within confined spaces such as buildings and tunnels. The City of Los Angeles has specific regulations in place governing new construction within a designated “Methane Zone”. However, many existing buildings, which are exempt from the newer methane building standards, may require special attention when such properties change hands. New property owners and institutional capital partners look at potential vapor migration and explosive hazards as environmental risks which require mitigation. In cases where the source of methane is clearly from an on-site source, the costs of mitigation measures would generally be expected to be borne by the property owner and/or developer. However, in cases where there is evidence of methane migration from off-site sources, and potential commingling of biogenic and petrogenic sources of methane, the use of environmental forensic techniques and specialized sampling programs can be beneficial in determining responsibility for the mitigation costs. This presentation will review general methane characteristics, methane concentrations and implications to redevelopment projects, methane sampling/monitoring methods, and forensic analytical techniques.