Honolulu’s largest waste water system update is now finished after six years in the making.

Mayor Kirk Caldwell formally announced the completion of the $375 million project during a press conference Thursday afternoon. 

The new sewer system is the first of its kind in Hawaii and uses gravity instead of electricity to funnel waste water to treatment.  

Specifically, waste water from a pre-treatment facility in Kaneohe travels through a gravity tunnel to a treatment plant in Kailua. 

Along with this three-mile-long underground gravity tunnel, the Kaneohe-Kailua Wastewater Conveyance and Treatment Facilities Project also includes a new pump station, headworks, a generator building, odor control facilities and a tunnel influent facility. 

The project will save taxpayers’ money on energy costs and substantially reduce the likelihood of sewage spills. Since the rebuilding of the sewage system, sewage spills have dropped by 73 percent, according to Caldwell.

“Our team has created a world class sanitation facility that will last for generations, while also protecting the environment that’s so important to our island lifestyle,” Caldwell said.