Long-awaited improvement project to Hilo Wastewater Treatment Plant begins this month

The Hilo Wastewater Treatment Plant, which was built in the early 1990s, will soon undergo its first significant improvements.

After years of deferred maintenance, Hawaiʻi County entered into an Administrative Order on Consent with the U.S. Environmental Protection Agency in March of 2024 to bring the facility and related infrastructure into compliance.

The facility serves about 30,000 residents in Hilo, and treats an average of 3 million gallons of wastewater daily.

“This project is well overdue and we are far behind,” Hawaiʻi County Mayor Kimo Alameda said on Thursday. “There is so much waste coming to this place in Keaukaha, and this community has been burdened by wastewater, the landfill, the airport. But we cannot change the past. We can improve the future by making sure this is done right and on time.”

The county awarded the $337 million contract to Honolulu-based Nan Inc. to address the critical infrastructure needs as part of the Hilo Wastewater Treatment Plant Rehabilitation and Replacement Project. The expected completion date is 2030.

The project focuses on rehabilitating the primary and secondary treatment facilities by replacing infrastructure and integrating modern technology. Work will be done in phases to ensure the plant remains operational during construction.

“The tricky part about this project is that we have to keep the facility going … during construction,” said Wesley Segawa, director of the county’s Department of Environmental Management. “This project will require careful scheduling so nothing will interfere with daily operations.”

Earlier this year, Alameda signed an emergency proclamation to allow the county to act quickly in the event of a failure at the plant or within the sewer system. It provides flexibility to access emergency resources, streamline procurement, and coordinate with state and federal agencies to support public safety during construction.

Alameda also directed staff to develop a response and mitigation plan so the county is prepared to address a sewage spill at any critical infrastructure location.

Some large discharge events during the past few years highlighted the need for the plant’s renovation.

An estimated 607,000 gallons of non-chlorinated, secondary treated effluent wastewater was discharged last June into Hilo Bay from the Hilo Wastewater Treatment Plant. The county Department of Environmental Management said the problem happened due to a failure of the chlorination system that occurred when chlorine was being replenished.

An even larger discharge occurred in November 2022 from the Hilo plant.

Hawai‘i Department of Health officials advised the public to stay out of waters from Puhi Bay to Onekahakaha in Hilo because an estimated 2.2 million gallons of partially treated sewage spilling into Hilo Bay.

“This is something Keaukaha has talked about improving the quality of Puhi Bay for years and no one has truly addressed it until now,” said Kaʻaka Swain, president of the Keaukaha Community Association. “Weʻre taking baby steps, but weʻre glad to be at this point.”

On Thursday, the County of Hawaiʻi held a groundbreaking to celebrate the beginning of these critical and long-needed upgrades and improvements to the treatment plant.

“Today’s groundbreaking marks a turning point,” Segawa said. “We know what is at stake and we will be moving forward with urgency and care. This plant must come into compliance. Our community deserves a wastewater system they can count on, and we are committed to seeing the project through with integrity, transparency and responsibility.”

The improvements to the Hilo Wastewater Treatment Facility include:

• Headworks: A new headworks facility will completely replace the existing structure. New screening, grit removal, flow metering and odor control systems.
• Primary Sedimentation Tanks: Repairs and replacements of aging concrete, valves, sludge collection equipment and odor control systems to maintain efficient solid separation.
• Secondary Clarifiers: Upgrades to valves, sludge collection, effluent launders, and pumps to enhance water clarification and sludge removal.
• Effluent Disinfection: Improved chemical feed, monitoring, and control systems for more effective disinfection of treated wastewater.
• Sludge Blending: New blending tanks and mixing systems to optimize sludge processing before thickening.
• Sludge Thickening & Dewatering: Construction of a new solids handling building with modern thickening and dewatering systems to improve biosolids management and odor control.
• Anaerobic Sludge Digestion: New digesters and control systems to enhance sludge stabilization and biogas management.
• Pump Stations: Replacement of on-site pump stations to ensure smooth wastewater flow and system efficiency.
• Electrical System Upgrades: Modernization of the plant’s electrical infrastructure, including a new switchboard, backup generator, and improved climate control for electrical rooms.
• Instrumentation & Control: Installation of a new SCADA system for automated monitoring and control of plant operations.
• General Site Improvements: Utility extensions, paving, grading and a new warehouse to support plant operations.

“This is the largest project in Hawaiʻi County where everyone is a stakeholder, so doing this work is an honor for us,” said Jason Ko, vice president of Nan Inc. “I know people are wary about the price tag, but this project is going to provide quality jobs for a lot of local guys and will improve life for everyone.”

While the improvements will upgrade the current system, Alameda also said he has done research on wastewater reclamation, which would ultimately clean the water enough to be used elsewhere, instead of going into the ocean.

“I’ve seen other places create a marsh, or we could turn it into a bird sanctuary,” Alameda said. “We can keep our thoughts open to always improve on what we have.”

Alameda said the county will have quarterly meetings with the project designers, department heads, Nan Inc. and the Wastewater Treatment Plant employees to make sure all issues are addressed immediately and the work is done thoroughly.

Alongside this project, the Department of Environmental Management is actively hiring for the Wastewater Division. Opportunities are available in engineering, operations, technical support, maintenance and leadership.

The department will hire both entry-level and experienced candidates who want to protect public health, preserve the environment, and support Hawai’i Island’s infrastructure. Open jobs can be found on the County of Hawaiʻi website.

Residents can stay up to date on the treatment plant rehabilitation. Visit the Department of Environmental Management’s website. There is also an option to sign up to receive email updates related to the project.