Operated by El Dorado County the Union Mine Landfill had been active since 1962. The facility ceased operating as a public disposal facility in 1996. The original portion of the landfill has undergone final closure. The remaining active area receives only sludge cake from the onsite wastewater treatment plant. The wastewater treatment plant currently processes septic tank waste (septage) and liquid waste from the landfill (leachate). The landfill has three leachate collection systems and the landfill gas collection system.

Carlton furnished professional services for El Dorado County throughout the closure process. Initial surveys, field density testing, permeability testing and reports have been provided. Additionally, Landfill Water Quality consulting and mitigation services and Phase II Soil Assessment and Environmental site reconnaissance. Subsurface exploration and reports were required for Installation of gas probes after the closure of the site.