Wildcat Interceptor Sewer Upsizing Project

The Wildcat Interceptor Sewer Upsizing Project is a major wastewater collection system upgrade for the City of Flagstaff Water Services Department. The project replaces approximately 5,700 linear feet of existing 33-inch interceptor sewer main with a parallel 48-inch HDPE pipeline. Once complete, the new interceptor will convey flows from upstream sanitary sewer lines to the Wildcat Wastewater Treatment Plant.

NWPX Geneva is supporting this project with 18 Perfect Lined Manholes. The 84-inch diameter manhole systems include lined precast bases, riser sections, and flat lids—each manufactured with a chemical- and abrasion-resistant synthetic polymer liner integrally cast into the concrete for long-term performance in wastewater environments.

The lined manhole components connect using an integrated SDV-Seal Manhole Gasket, creating water- and gas-tight joints and eliminating the need for field welding of the interior liner. Manhole heights range from 8.15 feet to 16.27 feet, with each structure configured with two 48-inch inlet/outlet openings to connect to the HDPE interceptor line via flexible rubber boots.

Installation was efficiently completed by Eagle Mountain Construction using standard equipment—no specialized tools or training were required. Eliminating field welding saved labor hours while reducing risk and expediting the installation process.

The City of Flagstaff’s upsized sewer interceptor expands wastewater capacity to accommodate projected growth over the next 50 years. The use of corrosion-resistant infrastructure, including NWPX Geneva’s Perfect Lined Manhole System, helps the new system meet the community’s long-term service needs by mitigating the risk of sanitary sewer overflows and service disruptions associated with microbiologically influenced corrosion in high-flow interceptor environments. This approach reduces future maintenance, rehabilitation, and replacement costs while supporting reliable wastewater conveyance for decades to come.