Honouliuli wastewater treatment plant finishes upgrades ahead of consent decree deadline

May 14, 2024
The Honouliuli WWTP finished its upgrades ahead of a 2010 consent decree deadline.

Honolulu Mayor Rick Blangiardi on May 10, 2024, commemorated the full secondary treatment upgrade of the Honouliuli Wastewater Treatment Plant (WWTP).

The upgrade totaled $536 million and included the installation of aeration basins, a blower building equipped with turbo blowers, a mixed liquor distribution box, secondary clarifiers and a secondary process pump station.

Improvements were also made to various parts of the primary treatment process along with upgrades to civil infrastructure, electrical systems and SCADA technology.

The work was completed to fulfill a 2010 consent decree. It halted years of legal action including a Sierra Club lawsuit, the 2007 Beachwalk lawsuit and resolved litigation over secondary treatment waivers, along with U.S. Environmental Protection Agency (EPA) and Hawai’I Department of Health (DOH) compliance orders, according to a press release.

The negotiated consent decree included three phases and a 25-year implementation schedule­—the longest timeframe allowed by the EPA.

Phase 1 was an upgrade of the sewer collection system. Phase 2 was the secondary upgrade of the Honouliuli WWTP. Phase 3 is the secondary upgrade of the San Island WWTP.

The city spent approximately $1.3 billion in capital costs on the Phase 1 upgrades to the collection system. This included approximately 2,100 miles of pipe, 72 wastewater pump stations and associated force mains. The city collects and treats nearly 100 million gallons of wastewater daily according to the press release.

The secondary upgrade of the Sand Island WWTP is being accomplished in two phases. The first is currently 50% complete and expected to be finished in 2026. The second phase is scheduled to being in 2026 and be completed by the consent decree deadline of December 31, 2035.

The Sand Island plant is currently an enhance primary plant that includes ultraviolet disinfection of effluent prior to discharge through a deep ocean outfall.

The Honouliuli facility was initially commissioned in 1978 as a primary treatment facility, but was later upgraded to partial secondary treatment in 1996. It has now been elevated to full secondary treatment capacity. The new plant was commissioned in January and has now been turned over to ENV operations staff ahead of the consent decree deadline of June 1, 2024.

The press release states that Honolulu ratepayers have had to bear the burden of funding the consent decree mandated projects.

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