The City & County of Honolulu’s Department of Environmental Services kicked off a $517 million construction project Friday to upgrade the Honouliuli Wastewater Treatment Plant.

“This project is a testament to the city’s dedication to improving infrastructure, embracing sustainability and ensuring a cleaner, healthier future for Honolulu,” Mayor Rick Blangiardi said in a news release. “As the plant undergoes this transformative phase, we look forward to the positive impact it will have on our community and the environment.”

The Honouliuli wastewater plant’s Phase 1-C will focus on overhauling the its pre-­treatment, primary treatment and solids processing systems, which have been in use since the 1970s.

“The plant is a critical infrastructure asset for our community, and these upgrades show our commitment to sustainability and resource recovery,” Environmental Services Director Roger Babcock said in the release.

Through the project, the plant’s pre-treatment process will be renewed to “enhance protection against inorganic debris,” while the plant’s primary treatment and solids processing systems will be improved to increase their efficiency while generating “valuable biogas.”

This biogas will be used to generate heat and electricity for the plant, which will reduce demand on Oahu’s energy grid as well as operating costs, which aligns with the city’s renewable-energy goals, according to Babcock.

The project was awarded to the Hensel Phelps Construction Co. and has a six-year timeline. It will be executed in three “strategic phases” that will involve installing and testing the electrical, structural and mechanical systems as well as grading, infrastructure development, underground piping and decommissioning and demolishing the existing facilities.