Intricate Solid Waste Plans Begin the Transformation at Puente Hills Regional Park

Efforts to Preserve the Landfill Soil Cover System and Install a Landfill Gas Collection System Underway

At Puente Hills Regional Park (PHRP), we’re partnering with the Los Angeles County Department of Public Works to transform a 700-acre landfill – formerly the second-largest landfill in the U.S. – into the county’s first new regional park in 30 years. The regenerative project features an environmental justice center to welcome visitors and 140 acres of nature trails and recreational spaces, aiming to empower the community and foster impactful environmental stewardship.

Transforming a Landfill into a Park

Intricate work is underway to lay the groundwork for a safe landfill transformation. Our waste team investigated the site and identified methods for park development that would maintain the performance of the landfill’s soil cover system, which was installed in accordance with regulatory requirements when the landfill closed in 2012.  

Conceptual plans approved by the Los Angeles Board of Health, the Regional Water Board and CalReycle included select soil placement for accessible routes, landscaping and play areas as well as modifications to protect sensitive landfill gas collection and other infrastructure from curious park visitors. Detailed plans to construct a methane mitigation system beneath the environmental justice center and other support buildings were also prepared. Now nearly complete, the mitigation system includes geomembrane barriers with connections to building foundations, a passive venting system, monitoring probes and continuous methane monitoring systems within the building to protect all occupants in enclosed spaces. 

Hilda L. Solis Environmental Justice Center

PHRP highlights an intriguing aspect of HDR – deeply experienced engineering and architecture teams within the same organization. As our solid waste team works to safely prepare the landfill for transformation, our architecture team designed the park, and its focal point, the Hilda L. Solis Environmental Justice Center (EJC). The EJC will demonstrate the best of today’s sustainable practices and rethinking waste through recycling, composting and salvage, featuring an immersive exhibition, classrooms, a makerspace, a lecture hall, an outdoor amphitheater, a media studio and a special enclosure to meet “animal ambassadors.”  The design is on target to achieve LEED Gold, net zero energy (operational carbon), a 50%+ reduction in embodied carbon and a 50% reduction in potable water consumption.

Next Steps for the Landfill Transformation

As the EJC construction completes, we’ll develop detailed grading plans for the initial park elements, landfill gas collection system relocation and protection systems, access roadway reconstruction, developing parking areas, stormwater management improvements, and incorporating landscaped areas, walkways and recreational areas on the western deck of the closed landfill.