Kihei Effluent Reuse System - Fukunaga & Associates, Inc.

Introduction

Aerial view of the Kihei WWRF

Kihei is located on the arid south side of Maui. Potable water for the region must be piped over ten miles from water wells drilled into the Iao Aquifer located near Wailuku. The community uses approximately 65 percent of this water for irrigation with the remainder ultimately ending up in the sanitary sewer system. This wastewater is then conveyed to the County of Maui’s Kihei Wastewater Reclamation Facility (WWRF) for treatment and disposal.

The Kihei WWRF is an activated sludge treatment facility that currently has a peak dry weather capacity of 8 million gallons per day (mgd). The facility has undergone major upgrades in its treatment capabilities with the addition of flocculation and chemical feed units, effluent filtration, ultraviolet disinfection, and renovations to the operations building. The plant is capable of producing R-1 effluent, which is the highest quality of effluent designated by Hawaii State Department of Health (DOH) Standards. Because R-1 effluent must undergo a high level of treatment, it has minimal restrictions for reuse.

In the past, the County of Maui has had difficulty in finding users for the reclaimed water, primarily because of the high cost of conveying the effluent to individual users. With the assistance of Fukunaga & Associates, Inc. (FAINC) and the cooperative efforts of surrounding landowners, potential users and the County, a functional system was constructed that meets the needs of the users, best utilizes existing facilities at the Kihei WWRF, and provides sufficient storage and transmission capabilities.

Project Descripion

Extent of the Kihei Effluent Reuse System

The County has constructed the major elements of the effluent reuse system that includes the primary storage facilities, as well as a major portion of the transmission and distribution system. These improvements have been installed in two projects: the Kihei Effluent Reuse Core System and the Kihei Effluent Reuse Distribution System, Phase I. The initial project, the Effluent Reuse Core System, qualified as an innovative project and was eligible for a 100 percent low interest loan from the State Revolving Fund (SRF), administered by the DOH.

The bids received on the project were very favorable, and with minimal change orders required during construction, a surplus of funds was available at the Core Project’s completion. A second project, the Kihei Effluent Reuse Distribution System, Phase I, was added and provided a major distribution arm for the system, serving the area north of the Kihei WWRF.

Kihei Effluent Reuse Core System

The modifications had to be phased and scheduled to minimize impacts on WWRF functions, since the facility had to maintain operations throughout the project construction

1.8 million gallon effluent basin

period. Major elements at the Kihei WWRF that were incorporated into the reuse system included the effluent pumping station, equipped with two 1500 gpm pumps, and the 1.8 million gallon effluent storage basin.

The existing effluent storage basin was rehabilitated and retrofitted with a polypropylene liner and floating membrane cover system to maintain the high quality of the treated effluent produced at the facility. The membrane liner and cover protect the effluent from debris and contaminants, and reduce the potential for algae growth.

1.0 million gallon concrete reservoir

New improvements included in the Core System project were designed to operate in concert with the existing facilities, and are also capable of functioning under expanded operating conditions as the plant capacity is increased in the future. The new improvements include a 1.0 million gallon reinforced concrete reservoir constructed with an aluminum geodesic dome cover, and an 18-inch ductile iron pipeline to connect the reservoir to the reclamation facility.

The dome cover eliminated the need for interior columns and footings within the reservoir, and the resulting cost savings allowed for the installation of a high quality tank lining system. The storage and transmission system is also equipped with remote pressure and flow sensors and level controls that communicate with the Kihei WWRF control station. Due to the reservoir’s remote location, level sensors at the tank utilize solar powered radio transmitters to communicate with the WWRF control station, thus eliminating the need for conventional power and communication lines. The telemetry system enables system operation and status checks through the plant’s Supervisory Control and Data Acquisition (SCADA) System.

Monsanto Corporation seed corn field

The Core System was put into operation prior to being fully completed so that it could continue to serve Monsanto Corporation’s seed corn operations and the Elleair Golf Course. Cooperation between effluent consumers, the County and the Contractor, Hawaiian Dredging Construction Company, allowed virtually uninterrupted service during the construction period. The total project construction cost for the Kihei Effluent Reuse Core System was $3.2 million. Total project construction time was 12 months with the project substantially completed in April 1998.

Kihei Effluent Reuse Distribution System, Phase I

Community interest in utilizing reclaimed effluent and the surplus funding available from the initial project prompted the County to extend the effluent distribution capability of the Kihei Effluent Reuse Core System. The Kihei Effluent Distribution System, Phase I

Kihei Community Center Playfield

was initiated during the construction phase of the Core System. Planning, design and bidding of the project was accomplished prior to the completion of construction for the Effluent Reuse Core Project. One of the goals of the project was to complete construction of the distribution system before to the completion of the Kihei Community Center, allowing the effluent to be used for the establishment of the playfields being constructed at the Center.

Fire hydrant painted purple to identify it as part of the reclaimed water system

The Phase I Distribution System included the extension of the effluent transmission line from the Kihei WWRF in the makai direction, across Piilani Highway, then northward along the proposed North-South Collector Road corridor to the Kihei Community Center site. Approximately 6,200 linear feet of 12-inch, and 1,700 linear feet of 18-inch, ductile iron pipe was installed for this project. The system serves the Kihei Community Center, Kihei Elementary and Lokelani Intermediate Schools, Haggai Institute and the Piilani Commercial Center. The effluent line was also outfitted with fire hydrants to aid firefighters in control of brushfires that frequently occur in the area. Per DOH standards, the fire hydrants are painted purple to identify them as part of the reclaimed water system.

The construction cost for the Kihei Effluent Distribution System, Phase I, was $682,000. Total construction time was 8 months, with substantial construction completed in December 1998. The contractor for the project was Goodfellow Brothers, Inc.

Consultant’s Role in Project

As the prime engineering consultant, Fukunaga & Associates, Inc. worked with the County of Maui on the project from its inception, handled the planning and design, and assisted during construction. A major concept that needed to be accepted by users of the system and the general public was that the treated effluent should be considered as a commodity having value and not simply as something that just needed to be disposed of. The high quality of the effluent needed to be preserved throughout the storage and transmission process to foster user confidence and minimize operational and maintenance problems. The availability of covered effluent storage, coupled with the installation of a pressurized distribution system allowed maximum flexibility for the County and the users of the system. The pressurized system allows users to simply tap into the system without the need for booster pumping.

A major challenge was to best utilize existing facilities at the Kihei WWRF without compromising the function and operation of the final effluent reuse system. Pumping unit capabilities were tested and evaluated to insure that the existing units would function effectively in the finished system, as well as during the transition period while the system was in construction. The refurbishing of the existing effluent storage basin by installing a membrane lining and floating cover provided a significant improvement in preserving the system’s effluent quality. Coordination and phasing of the work was also crucial in maintaining service to existing system users and in avoiding interruption of treatment facility operations.

The subconsultants, MK Engineers, Ltd. and Shigemura, Lau, Sakanashi and Higuchi, Inc. (SLSH), provided electrical and structural engineering services, respectively. MK Engineers, Inc. worked with the County staff and vendors of Supervisory Control And Data Acquisition (SCADA), radio and solar power systems, to develop a solar powered reservoir level control system linked by a radio telemetry system to the County’s SCADA system and effluent pumping station at the Kihei WWRF. The SCADA system is programmed to start and stop the effluent pumps and to control valves that permit irrigation of the Elleair Golf Course and the Monsanto Corporation’s seed corn operations. SLSH worked with the County to optimize the storage reservoir design, utilizing an aluminum geodesic dome cover, in lieu of a conventional concrete roof slab, resulting in cost savings for the County.

Conclusion

The Kihei Effluent Reuse System has met its goal of providing the County of Maui with a system that is beneficial to the community by preserving its potable water resources, and utilizing reclaimed water for irrigation of parks, landscape areas and a golf course, and for fire protection. The reclaimed water is also used by a major agricultural operation, Monsanto Corporation, for the production of high quality seed corn that is marketed worldwide. The system has proven to be easy to operate and reliable, and has met the needs and expectations of the County.

The Kihei WWRF currently reclaims between 40 and 50 percent of the wastewater it treats, typically between 1.6 and 2.0 million gallons per day. The rest of the treated effluent is discharged through injection wells located on the WWRF site. It is envisioned that the Kihei WWRF will eventually reclaim 100 percent of its flow as public acceptance and demand for the high quality effluent increases in the future.