Pearl Harbor Channel

Project Description

The existing 24-inch cast-iron water transmission main supplying potable water to Ford Island and the Pearl Harbor Naval Shipyard was over 65 years old and exposed on the harbor floor. In 2006, the vulnerability of this critical line was revealed when a construction vessel accidentally damaged it by dropping an anchor, prompting the need for immediate infrastructure improvements. Originally installed in 1952, the aging pipeline had reached the end of its service life.

To enhance system reliability and eliminate future risk, a new 24-inch fusible polyvinyl chloride (FPVC) water main was installed beneath the Pearl Harbor Channel using horizontal directional drilling (HDD). This trenchless method positioned the pipe below the channel bottom, reducing environmental impact and avoiding disruption to harbor operations.

The design faced several technical challenges, including varying subsurface conditions (from soft sediments to hard rock), a 3,500-foot pull length, high thrust forces on large-diameter fittings, and the need to connect to existing major transmission lines. Despite these complexities, the project successfully delivered a more secure and resilient water supply for the U.S. Navy.

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Consultant's Role in TheProject

Fukunaga & Associates, Inc. (FAINC) served as the lead engineering consultant and civil design engineer for the project. As the prime consultant, FAINC managed all aspects of project coordination with Naval Facilities Engineering Command (NAVFAC) Pacific, NAVFAC Hawai'i as the system owner, and the supporting sub-consultant team.

Design Considerations

A key objective of the project was to improve the efficiency and reliability of the Navy's water system serving Pearl Harbor. By installing the new waterline below the harbor channel using trenchless technology, the design significantly reduced the risk of future damage from surface vessel or underwater activities. In addition to enhancing system security, the project increased water transmission capacity and provided critical backup capability to maintain uninterrupted service across base operations.

The use of horizontal directional drilling (HDD) minimized environmental impact, particularly during the underwater crossing. Careful planning ensured that harbor bottom sediments - potentially containing hazardous materials - were not disturbed, thereby protecting surrounding waters from contamination.

Corrosion resistant pipeline materials were selected to ensure long-term performance and durability. Essential components, such as valves and expansion couplings, were installed in accessible concrete vaults, allowing for maintenance or replacement without the need for major excavation, further reducing future disruption to the area.

Innovative Use of Existing Technologies and materials

The Pearl Harbor Channel underwater waterline crossing showcased how existing technologies and materials can be adapted in innovative ways to achieve effective and efficient infrastructure solutions. The use of a high-strength, fusible pipe material enabled installation via horizontal directional drilling (HDD) without the need for a protective casing or more expensive alternatives like microtunneling. The continuous 3,500-foot pipe string was successfully pulled through the bore in a single day, minimizing disruption to nearby residences and maintaining uninterrupted Naval operations during construction.

Complexity

The project required careful consideration of multiple design factors to successfully implement the modified horizontal directional drilling (HDD) method. Key elements included ensuring proper vertical alignment to maintain minimum bend radius, calculating pulling loads on the fusible PVC (FPVC) pipe, and evaluating long-term pipeline stability through estimates of estuarine soil consolidation. Borehole stability, potential heave, and the risk of hydro-fracture were assessed under various drilling fluid conditions to mitigate construction risks.

Construction oversight played a critical role in project success. Offshore navigation of the drill head was carefully monitored to maintain precise bore alignment and avoid high points in the pipeline profile. Pull loads were continuously tracked to prevent overstressing the pipe, which could compromise its pressure rating and long-term durability.

Additional design challenges included adequate burial depth below the harbor mudline and avoiding interference with existing utilities, structures, pile-supported docks, and historic features. The planning process also required identifying suitable staging and work areas in both Pearl Harbor and Ford Island to accommodate the layout of the full-length fused pipe string for continuous installation.

Conclusion

Fukunaga & Associates, Inc. (FAINC) and the design team provided comprehensive support throughout all phases of the project - from initial concept through design development and final completion - working in close partnership with both the project manager, NAVFAC Pacific, and the system owner, NAVFAC Hawai'i. As with many public infrastructure projects, controlling construction costs was a significant challenge. While the original budget was set at $11.29 million, the final bid came in at $10.04 million. This cost efficiency is largely credited to the innovative design of the under-channel waterline crossing.

The long-term value of the project lies in the increased reliability of the Navy's water infrastructure. The new waterline provides a secure and durable supply to Ford Island, enabling continued development into a thriving commercial, visitor, and operational hub within Pearl Harbor.

The project was completed on time and within the design budget. It was advertised for bid in 2012, with construction beginning in 2013 and substantial completion achieved in 2015 - successfully meeting all project milestones.