Hidden Hollow Partial Closure

Ada County has been managing the County’s municipal solid waste at the landfill since 1972. The majority of the waste has been deposited in the Hidden Hollow Cell. As the Hidden Hollow cell nears capacity, the County has started the process of installing its cap.

Capping a landfill requires a final, thick layer of soil be put in place, and then native vegetation is planted to blend in with the natural surrounding landscape.

About half of the Hidden Hollow cell was capped in Stage 1 about 10 years ago. This project will cap and close another portion of the Hidden Hollow cell and move the primary operation to the highly engineered, fully lined North Ravine cell.

• Design work for excavation includes drawings and specifications for the regulatory soil cap.
• Detailed requirements and qualifications for construction.
• Construction schedule and requisite documents for review by various regulatory agencies and the general public.
• Hauling and placement of soil cap soils.
• Continuous monitoring for gas emissions and groundwater contamination according to regulatory requirements.

• Help reduce odors by preventing landfill gas from escaping through the landfill.
• Native vegetation planted to blend in with surrounding landscape.
• Daily operations and depositing of municipal solid waste moved to the fully lined North Cell Ravine.

Ada County Operations
Telephone: (208) 287-7100