Landfill gas is roughly half methane, produced as buried organic waste decomposes without oxygen. That gas does not stay put – it migrates laterally through soil, sometimes hundreds of feet beyond a landfill’s boundary. This is why Los Angeles building officials treat landfill proximity as a trigger for methane investigation, commonly for projects within about 1,000 feet of a current or former disposal site.
How Landfills Produce Methane
Once waste is buried, anaerobic bacteria break it down and generate landfill gas for decades – long after a site closes. Closed and capped landfills can keep producing gas at meaningful rates for 30 years or more, and older, unlined sites allow that gas to move freely into surrounding soils.
Los Angeles Lives With Its Landfill Legacy
The region is dotted with closed landfills that now sit next to – or under – parks, golf courses, and neighborhoods: Toyon Canyon in Griffith Park, Sheldon-Arleta in the Valley, Puente Hills (once the largest landfill in the country), and Scholl Canyon above Glendale, where the golf and tennis facility was built with methane mitigation for exactly this reason.
When Methane Testing Is Required
LADBS methane zone and buffer zone maps capture many landfill-adjacent parcels, and plan checkers can require a methane investigation for any project near a disposal site. A soil gas survey measures methane concentration and pressure beneath the site, which determines the mitigation level your design must meet.
Mitigation Options Near Landfills
Where testing finds elevated methane, solutions range from passive sub-slab vent systems and impermeable membranes to active extraction – engineered through methane mitigation design and installed during construction.
Building near a former landfill does not have to derail a project. Sway Features handles LADBS methane testing and mitigation across Los Angeles – reach out before plan check and know exactly what your site requires.