- ENGINEERING INFO
- CASE STUDIES
In late 2014, the Pearl City Peninsula to Ford Island Waterline Crossing Project was completed, replacing approximately 3,800 LF of deteriorated 24-inch cast iron water main. The new pipeline will serve as a primary artery connecting the existing Pearl Harbor Complex with its primary potable water source in Waiawa. The project supports the mission of COMNAVREG (Commander, Navy Region) Hawaii by supplying an efficient and safe transmission line to provide potable water and fire protection to Ford Island, the Pearl Harbor Naval Shipyard, and Hickam Air Force Base.
Approximately 3,500 LF of the new waterline was installed using horizontal directional drilling (HDD), with the balance installed by open-cut. The HDD alignment crossed under the Naval Special Warfare (NSW) Compound and the Pearl Harbor channel before surfacing on Ford Island. HDD offered a feasible and cost-effective means of installing the pipe through the very soft harbor sediments. Directional drilling has been used successfully on previous underwater crossings in Pearl Harbor for both sewer and water pipelines.
Design phase planning addressed many considerations, including selection of an alignment and profile to tie into the existing waterline. Other key design parameters included ensuring adequate cover below the harbor mud line and avoiding existing utilities, ammunition bunkers, pile-supported docks and buildings, and other structures. The design phase also required selection of appropriate work and staging areas both within the NSW Compound and on Ford Island, where the entire fused pipeline could be laid out for continuous pull-in. Finally, the design required selection of pipe materials appropriate for the soils and direct-pull installation. Fusible PVC® pipe was specified for the HDD installation based on its extensive track record in long distance HDD installations and resistance to corrosion, hydrocarbon permeation, and water disinfectant induced oxidation. The safe pull force, bend radius, and buckling pressure of Fusible PVC® pipe facilitated the direct pull installation with the vertical curves and deep profile required by the crossing.
The HDD alignment included a horizontal curve through varying subsurface conditions which included soft slurry-like estuarine deposits, coralline deposits interbedded with coral limestone, stiff alluvial deposits, contaminated fill materials, and possible submarine slope failure. The geological conditions necessitated strict qualification requirements for the HDD subcontractor and workforce, and thorough HDD specification requirements. Additional specification requirements included detailed construction submittals for the HDD work plan, a pipe fusion work plan and a hydrostatic test plan.
The HDD portion of the project was completed in October 2014, with only the remaining tie-ins to the existing water system on both sides of the crossing to be completed.
Art Lambert of Healy Tibbits commented: “UGSI was a terrific supplier and partner from start to finish in providing HTBI everything necessary to complete this very technical portion of the project in a high quality manner, on time, and within the budget. The strong relationship developed with UGSI on this project and previous projects helped overcome the many challenges associated with installing 3,500 LF of 24-inch Fusible PVC® pipe under Pearl Harbor in one day. HTBI will definitely be looking forward to working with UGSI on future projects that utilize Fusible PVC® pipe.”
|Pipeline Details and Project Summary|
|Project:||Pearl City to Ford Island Waterline Crossing|
|Location:||Pearl City, HI|
|Pipe Size:||24” DR18 Fusible PVC®|
|Pressure Test:||200 psi|
|Installation:||Horizontal Directional Drill|
|Engineers:||Fukunaga and Associates, Yogi Kwong Engineers|
|Contractor:||Healy Tibbitts (General), Southeast Directional Drilling (HDD Subcontractor)|