Construction has begun on a $174m upgrade of Honolulu’s Sand Island Wastewater Treatment Plant, increasing the capacity and efficiency of the state’s largest plant.

The scope of work includes expanding the facility’s existing bioconversion capabilities, relocating and reconstructing the effluent water reuse pump station, while removing old utilities and adding new ones.

Synagro Technologies is acting as the design-build contractor, with Hensel Phelps handling construction and Yogi Kwong Engineers as construction manager.

The project is due to be completed by October 2028.