The Honouliuli Wastewater Treatment Plant (WWTP) Phase 1C – Headworks, HRBC, Solids Process and Miscellaneous Improvements project is part of a long‑term, multi‑phase initiative led by the City and County of Honolulu Department of Environmental Services. The program delivers major upgrades to both liquid and solids treatment processes, supporting wastewater treatment and environmental protection for Central and West Oahu.

Liquid stream improvements include modifications to the existing Influent Screening Facility, including the addition of two new screening channels and five new screens; construction of a new cast‑in‑place concrete grit removal facility; and conversion of the existing grit removal and aeration tank structure into a High‑Rate Biological Contactor (HRBC) process facility. The biologically enhanced primary treatment system includes five contactor tanks and ten dissolved air flotation (DAF) tanks, improving treatment performance and increasing sludge quality prior to solids processing.

Upgrades to the solids stream introduce a thermal hydrolysis process (THP) ahead of anaerobic digestion. This improvement increases biogas production while reducing digester residence time. Biogas generated through digestion will be used to power two 2.0‑MW cogeneration generators at the combined heat and power (CHP) faciltiy, supplying renewable energy back to the plant and reducing overall energy demand. Supporting these process improvements are significant electrical and controls upgrades, including new low‑voltage switchgear, motor control centers, programmable logic controllers (PLC) and enhancements to the SCADA system—supporting increased biogas generation and cogeneration at a combined heat and power facility.

The project is constructed through a sequenced, three‑phase program to support efficient commissioning: Phase 1, Liquid Stream Improvements; Phase 2, Solids Stream Improvements; and Phase 3, Perimeter and Site Facilities. Scheduled for completion in November 2029, the project will be part of a roadmap to address long‑term growth, resiliency, energy efficiency and environmental stewardship for the City and County of Honolulu.

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The City and County of Honolulu’s Sand Island Wastewater Treatment Plant (WWTP) Secondary Treatment Phase 1 project represents a major investment in Hawaii’s critical water infrastructure and environmental stewardship. This large‑scale upgrade modernizes the existing Sand Island WWTP to provide secondary wastewater treatmentÌýcompliantÌýwith aÌý2010 U.S. Environmental Protection Agency Consent Decree.ÌýÌý

Located on a 24‑acre site between Honolulu’s downtown business district and the airport, the project involves both new construction and significant rehabilitation of existing facilities. Once complete, the upgraded plant will treatÌý20 million gallonsÌýper day (MGD) using advanced membrane bioreactor (MBR) technology, significantly improving effluent quality before discharge through the existing ultraviolet disinfection system and ocean outfall.ÌýÌý

Key elements of the project include construction of a new Intermediate Pump Station and Blower Building, MBR service and processing facilities, sludge thickening and processing systems, enhanced odor control and new effluent flow routing, including tunnels and channels. The project combines new facilities with extensive renovations to the active treatment plant. Ìý

Delivered using a design‑bid‑build approach, the project requires complex sequencing and close coordination toÌýmaintainÌýcontinuous plant operations throughout construction. The work includes extensive cast‑in‑place concrete, below‑grade construction, dewatering and the installation of mechanical, electrical, instrumentation and process systems critical to wastewater treatment performance. Ìý

Scheduled for completion in December 2026, the Sand Island Wastewater Treatment Plant Secondary Treatment Phase 1 project will play a vital role in protectingÌýHawaii’s coastal waters, supporting publicÌýhealthÌýand setting the foundation for future wastewater treatment upgrades across the island.ÌýÌý

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The Kailua Regional Wastewater Treatment Plant Electrical Improvements project is a key component of the Kailua Regional Wastewater Treatment Plant’s long-term master plan. It advances the City and County of Honolulu’s goal of modernizing operations to handle increased wastewater flows and comply with environmental regulations. By upgrading the plant’s electrical systems, the project enhances efficiency and reliability, minimizing the risk of failures and service disruptions. It also strengthens resilience against natural disasters and emergencies while supporting future expansions and upgrades to other systems. These improvements are essential to ensuring the plant’s long-term viability and its ability to protect water quality and public health throughout the east side of Oahu.

The Kailua Regional Wastewater Treatment Plant Electrical Improvements project included both electrical and control upgrades across 13 buildings in an active facility. The scope included the integration of a new 15kV medium-voltage paralleling switchgear located at the Plant’s Service Entrance, which distributed power to five pairs of medium-voltage substation transformers. This infrastructure provides stable and redundant 480V power to critical processing areas. New low-voltage switchgears with automatic power control sequences were installed at the Effluent Pump Station and the old Kailua Influent Pump Station. Motor control centers were installed downstream of the low-voltage switchgear to provide automated power monitoring and controls to the remaining facilities throughout the plant. These improvements facilitated the removal of the two separate unstable HECO Utility feeds and backup generators, allowing the redundant Utility feed, backed up by the Plants Service Entrance 3-4MW generators, to serve as the central backup power source in case of utility interruptions.

In addition to the electrical improvements, new automated instrumentation and control systems were installed in the critical processing areas and integrated into the plant’s existing Supervisory Control and Data Acquisition (SCADA) system to improve operational management and monitoring. Architectural, structural, access controls, and HVAC enhancements were implemented to support the buildout of electrical rooms, ensuring they meet operational requirements and provide a safe, functional environment for new electrical equipment.

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Located at Marine Corps Base Hawaii, the Repair Water Reclamation Facility (WRF) Secondary Clarifier involves significant upgrades to the base’s WRF secondary clarifier to enhance its operational efficiency and reliability.

The primary scope of work includes the removal and replacement of the rotating sludge collection rake mechanism within the existing secondary clarifier. This essential component is responsible for the effective collection and removal of sludge, ensuring the smooth operation of the water reclamation process. Additionally, the project encompasses the replacement of the scum skimmer, sludge valves, and isolation valves on the inlet and outlet pipes, which are crucial for maintaining the integrity and functionality of the clarifier system.

To address environmental and safety concerns, the project also involves lead paint remediation, floor grout replacement, and tank coating. These measures are vital for ensuring a safe working environment and prolonging the lifespan of the facility. Furthermore, temporary modifications to the chlorine contact tanks, including slide and scum removal, and the installation of temporary effluent filter systems, are part of the comprehensive upgrade plan. These temporary systems will supplement the existing filtration and treatment processes during periods of inoperability, ensuring continuous operation and compliance with environmental standards.

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The Repair Wastewater Treatment Plant Effluent Pump Station Building 1357 stands as the Pacific Region’s first federal wastewater infrastructure project. Situated at Joint Base Pearl Harbor-Hickam in Hawaii, this initiative involves the complete replacement of the above-ground portion of the existing effluent pump station, along with all associated support equipment currently housed within Building 1357 and its adjacent areas.

Central to the upgrade is the installation of three high-efficiency 10 million-gallon-per-day vertical turbine pumps and a modern motor control center, which has a fully integrated Supervisory Control and Data Acquisition (SCADA) system. This advanced system brings a transformative leap in operational efficiency, reliability and user functionality. It enables precise control of wet well levels and leverages predictive diagnostics to reduce maintenance needs and minimize downtime through automation and supervision.

The integration of real-time monitoring and advanced SCADA programming fosters a comprehensive awareness of system performance, empowering operators to manage the facility proactively and build long-term resilience. The facility’s clean and functional layout, paired with an intuitive interface, enhances productivity and simplifies maintenance and system overhauls. Moreover, the new design ensures full compliance with evolving environmental regulations and reporting requirements, positioning the station as a model of modern wastewater management.

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51³Ô¹Ï served as the Construction Manager at Risk (CMAR) for the Town of Wellington’s Project. The plant’s capacity was increased to 4.2 million gallons per day (MGD), with accommodations for a future build-out capacity of 6.9 MGD. The new 15,352 SF treatment building was constructed over the two treatment trains and included an electrical room, pipe gallery, equipment room and observation decks over the basins. The 3,023 SF chemical building was built over eight chemical storage tanks in the concrete chemical containment structure, which included chemical feed equipment, an electrical room and a mechanical room.ÌýThe 1,998 SF ozone building was constructed over a two-level concrete foundation to house the ozone generation and injection equipment and electrical room.

The project included a pipeline ozone contactor, three solids drying beds, two equalization ponds, a recycle pump station, a backwash equalization pump station, modifications to the existing clearwell, connection to emergency supply from ditch, site and yard piping modifications and modifications to the existing chemical building. Additional work included site improvements, electrical, instrumentation and control and system start-up. The preconstruction phase included delivering a progressive GMP and the procurement of the ozonation system equipment. Additionally, announced the Wellington Water Treatment Plant Expansion as the 2025 Water/Environment Best Project.

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The South Fort Collins Sanitation District (SFCSD) project expanded the Water Reclamation Facility (WRF) to accommodate growth within the service area, increasing its capacity from 4.5 million gallons per day (MGD) to 6 MGD during Phase 1 (with provisions to expand to nine MGD in the future). This CMAR project included nutrient removal facilities to meet the limits of the Colorado Department of Public Health and the Environment Regulation 85.

Additional improvements to the solids handling facilities enabled SFCSD to reuse their biosolids (in compliance with 40 Code of Federal Regulations Part 503 biosolids regulation) as a Class A product. The project added several new facilities including a step feed aeration basin, blower building, secondary clarifier, Autothermal Thermophilic Aerobic Digestion (ATAD) and a biofilter. Components of the project included influent pumps, blowers, numerous pumps, a UV system and rotary drum thickeners. Other improvements included yard piping, grading, paving, electrical and instrumentation and control.Ìý

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The Town of Windsor hired 51³Ô¹Ï as the Construction Manager at Risk (CMAR) for the Wastewater Treatment Facility Biosolids Improvements project. The existing facility was more than 40 years old and had reached its operational capacity. The project entailed rehabilitation of the existing influent screens in the headworks facility, modifications to the existing non-potable water system in the operations building (replacement of pumps and piping), the installation of a parallel waste-activated sludge line, a new aerobic digester tank with three cells, a new three-story dewatering building and site improvements.

The project has helped the Town of Windsor to relieve capacity restraints on the lagoon system, meet future biosolids handling needs and reduce operating hauling and disposal costs. Despite unprecedented challenges with the supply chain caused by the pandemic, 51³Ô¹Ï delivered the project nearly $300,000 under budget.

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The South Fort Collins Sanitation District (SFCSD) Project expanded the Water Reclamation Facility to accommodate growth within the service area, increasing its capacity from 4.5 million gallons per day (MGD) to six MGD during Phase 1 (with provisions to expand to nine MGD in the future). This project included nutrient removal facilities to meet the limits of Regulation 85. Additional improvements to the solids handling facilities enabled SFCSD to reuse their biosolids (in compliance with 40 Code of Federal Regulations Part 503 biosolids regulation). The project added several new facilities: a step feed aeration basin, blower building, secondary clarifier, Auto Thermophilic Aerobic Digestion and a biofilter. Components of the project included rotary drum thickeners, influent pumps, blowers, pumps and a UV system. Other improvements included yard piping, grading, paving, electrical and instrumentation and control.

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The Drake Water Reclamation Facility Project entailed the construction of a new sidestream phosphorous removal system, including a new building with process equipment and mechanical and electrical work. The new cogeneration system involved recovering digester gas to generate heat and electricity, and included yard piping, concrete, electrical and controls and instrumentation, as well as the installation of a gas conditioner and two owner-furnished co-generators. This project also included process pipe modifications in the digester building; the installation of chemical metering pumps, skids and distribution piping for the north and south process train aeration basins; and the demolition and removal of the existing chlorine scrubber. The facility has the capacity to treat 23 million gallons per day (MGD) and manages the biosolids for both the Drake and the Mulberry Water Reclamation Facilities.

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