City officials marked a milestone in the multibillion dollar effort to upgrade Oahu’s sewer system as part of a consent decree that was reached between the Sierra Club and federal, state and city agencies in 2010.

Rebuilding the collection system cost $3.4 billion and was to take 10 years.

Mayor Kirk Caldwell said the Department of Environmental Services has reached 398 of 399 deadlines dealing with phase one of the consent decree that involves rebuilding the collections system. All were supposed to be completed by June 30.

The one outstanding segment is a section of the Waiakamilo Road Trunk Sewer Project, an area between Dillingham Boulevard and North School Street. Environmental Services Director Lori Kahikina said that segment has been plagued by bid protests, unforeseen utility work, contaminated soil and trouble hiring available off-duty police officers to assist with traffic.

The project was supposed to be done by June 30. The Environmental Protection Agency signed off on allowing a 14-month extension to Aug. 31, 2021, Kahikina said.

“So today, we’re 100% compliant,” she said. That first phase of the consent decree also has come in below the $3.4 billion estimate.

For more on the Awa Street Wastewater Pump Station Force Main and Sewer System Improvements program, go to awasewer.org.

Caldwell praised Kahikina for her department’s performance. Oahu recorded 200 sewage spills in 2006. That dropped to 31 in 2019 and there’ve been only 13 so far this year, he said.

The system includes 2,100 miles of pipes, 72 wastewater pump stations and associated force mains, Environmental Services said. More than 100 million gallons of wastewater are transported and treated by the city each day.

The second phase of the consent decree requires the Sand Island and Honouliuli treatment plants to be upgraded. Work on the Honouliuli upgrade began last year and is expected to be completed in 2024. The city has until 2035 to finish the Sand Island upgrade.