Hilo Wastewater Treatment Plant Rehabilitation and Replacement Project

 

PLANNED IMPROVEMENTS


Hilo Project Phase 1 Before

Site Layout of the Hilo Wastewater Treatment Plant, Pre-Construction

Hilo WWTP Project After

Site Layout of the Hilo Wastewater Treatment Plant, Post-Construction

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.

PROJECT MILESTONES


🟢

NTP

ISSUED

02/2025

🚧

CONSTRUCTION

START

7/2025

HEADWORKS

SYSTEM

10/2026

PRIMARY 

FACILITIES

DATE TBD

 SUBSTANTIAL

COMPLETION

DATE TBD

🎉

CONSTRUCTION

FINISHED

DATE TBD

  

NEWS


 

Groundbreaking Held for Hilo Wastewater Treatment Plant Upgrades

Post Date:07/31/2025 2:14 PM
The County of Hawaiʻi celebrated the groundbreaking of critical upgrades to the Hilo Wastewater Treatment Plant on Thursday, marking the beginning of construction on long-needed improvements to the wastewater facility. 

The $337 million upgrade project will replace outdated equipment, improve treatment efficiency, and strengthen environmental safeguards. Work includes construction of a new headworks facility, upgrades to primary and secondary treatment systems, new solids handling and odor control buildings, and major electrical and control system improvements. 

The project is being delivered by Nan Inc. and is scheduled to be complete in 2030.

Mayor Kimo Alameda, elected officials, County leadership, and project partners joined together at the plant site to recognize this milestone and emphasize the importance of investing in safe, modern wastewater infrastructure for the Hilo community. 

“Our wastewater system has needed attention for a long time, and we are finally turning that page,” said Mayor Alameda. “With this investment, we are making sure that the Hilo Wastewater Treatment Plant operates at the high standards our community deserves. In the meantime, we will be working closely with our contractors to keep everything running smoothly and safely. I want to thank our dedicated wastewater staff. They are the unsung heroes who keep these vital systems working day in and day out.” 

Originally built in the early 1990s, the facility serves approximately 30,000 residents and treats an average of 3 million gallons of wastewater daily. In March 2024, the County entered into an Administrative Order on Consent with the U.S. Environmental Protection Agency to bring the facility and related infrastructure into compliance.

“This project has been a long time coming, and today’s groundbreaking reflects the determination of everyone who’s kept this plant running while we worked to get here,” said Wesley R. Segawa, County Environmental Management Director. “We know how critical this facility is to the community, and this upgrade represents years of effort from our team, our partners, and the many people behind the scenes. Our operators, mechanics, lab staff, and engineers have held the line through challenging conditions. Now it’s our job to give them the tools and support they need to build a system the community can rely on for the long term.” 

To support public safety before and during construction, Mayor Alameda signed an emergency proclamation earlier this year. The proclamation allows 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. This proactive measure strengthens the County’s ability to respond swiftly to potential spills, protect public health, and safeguard the environment while construction is underway. 

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 welcomes both entry-level and experienced candidates who want to protect public health, preserve our environment, and support Hawai’i Island’s infrastructure. To learn more and apply, visit www.hawaiicounty.gov/jobs.  

The County invites residents to stay up to date on the treatment plant rehabilitation. Visit the Department of Environmental Management’s website for more information and sign up to receive email updates related to the project: www.dem.hawaiicounty.gov/projects/hilo-wastewater-plant. 
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FAQs

Will the upgraded plant be able to handle more wastewater?
The project restores or replaces critical facilities with reliable modern equipment, and new building structures.

Did the County consider other methods besides upgrading the existing plant?
Alternative technologies and approaches were evaluated during the planning phase of the project.

What level of treatment does the Hilo WWTP provide?
The Hilo WWTP provides secondary treatment with disinfection, as required by the NPDES permit.

Why did the County issue an emergency proclamation for the Hilo Wastewater Treatment Plant?
The emergency proclamation enables the County to take quick action to protect public health if the Hilo Wastewater Treatment Plant faces infrastructure failure during rehabilitation.

 

PROJECT TEAM


Contractor

Nan Inc

Builds the project using the right materials and crew, making sure it’s done safely, correctly, and on time.

Engineer of Record

Carollo Engineers

Designs the project, ensures it meets all safety rules and regulations, and follows approved plans.

Construction Management

TBD

Keeps the project on schedule and organized from start to finish.

 


 

 

CONTACT US

✉️ cohdem@hawaiicounty.gov

📞 808-961-8099