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Expect the Extraordinary.


City of Spokane ESD™ Egg-Shaped Digesters

The City of Spokane, Washington, selected APTIM to provide two Egg-Shaped Digesters. APTIM was responsible for the engineering, fabrication and construction of the vessels. The ESDs replaced a failed concrete structure. Located adjacent to the Riverside State Park along the Spokane River, this project presented challenges and sensitivity in design, environment and logistics. The tight terrain, existing facilities, river shoreline and osprey nesting area added to the degree of project difficulty.

Architectural enhancements included one equipment pilaster per vessel to hide pipe runs and one stair tower per tank including an elevator. Decorative walkways, metal cladding texture and color schemes were utilized to minimize visual impacts for residents on the bluff above and recreational park or river users below.The ESDs were built using a fixed tower crane located to maximize available ground space, minimize environmental disruptions and optimize utilization for equipment and other site lifting needs. This project was completed with restricted working hours for visual and noise considerations.  Each digester has an overall height of 112 feet 4 inches, a maximum outer diameter of 89 feet, and a capacity of 2,800,000 gallons.  

Contracting Entity: City of Spokane