South Chollas Yard Methane Leak
Owner: City of San Diego, Public Works Division
Location: 2781 Caminito Chollas, San Diego 92105
Designer: SWT Engineering
Contractor: Orion Construction Corporation
Delivery Model: Design-Bid-Build - T&M
Contract Value: $12.5 million
Schedule: January 2025 – February 2026
Scope: Construction of Landfill Gas Extraction system upgrades including 4,450ft of 6-inch and 8-inch HDPE fused pipe, ten vertical landfill gas extraction wells ranging in depths from 10ft to 31ft, six horizontal landfill gas extraction wells, and connections to the existing Landfill Gas Extraction system. Additional upgrades also included installation of a new 230,000sq.ft. landfill cover system composed of geotextile fabric, geogrid, and geomembrane. Final restoration included asphalt paving, striping, and installation of lighting for the South Chollas PUD Facility parking lot.
Challenges: The City of San Diego’s South Chollas PUD Facility is situated on a closed landfill that has faced issues with uncontrolled landfill gas releases, affecting the parking lot. Continuous air quality and soil monitoring during construction was necessary due to the potential hazards. Managing the underlying landfill materials involved preliminary testing and special waste profiling for safe removal. Close coordination was essential to maintain access to the parking lot during multiple construction phases. Given the landfill conditions, any work below ground posed risks, requiring an accelerated schedule to minimize the release of hazardous gases.
Results: The South Chollas Landfill Employee Parking Project upgrades the South Chollas PUD Facility in San Diego. It includes improvements to the Landfill Gas Extraction System, a new Landfill Liner Cover, and a replacement parking lot with a geomembrane for better landfill gas management and a geogrid for pavement stabilization. The City accelerated parts of the project, allowing early use of the parking lot. This initiative enhances safety for City employees and extends the facility's operational life.
