FY01 MCON Project P-491,
Sewer Force Main - Ford Island to Pearl Harbor Naval Shipyard

Contribution to the Well-Being of People and Communities

The project provides enhanced wastewater transmission capabilities from Ford Island. This increased transmission capacity and system reliability allows the Navy to proceed with the Ford Island Development Plan. The Development Plan provides critically needed housing for Navy personnel, muchneeded economic revitalization to the area, and an opportunity for the Navy to showcase the historical significance of Pearl Harbor and its vital role in U.S. military history.

Resourcefulness in Planning and Solving Design Challenges

The greatest challenge was installing the pipeline crossing under the 1200 ft wide and 50 ft deep Main Channel of Pearl Harbor. Major concerns were to avoid disrupting harbor operations, and restricting of the movements of Naval ships, key elements of our nation�fs defense force. Construction equipment and activity within the Main Channel could impair harbor operations. Another concern was to minimize adverse water quality impacts that could potentially affect the ecosystem and recreational activities in adjacent near-shore waters. Sediments on the harbor bottom may be contaminated due to heavy industrial activity conducted within the facility in the past.

Another major challenge was to avoid damaging the numerous historical features on Ford Island, including World War II vintage buildings and significant physical features resulting from the December 7, 1941 attack that propelled the U.S. into World War II.

To meet these challenges, the design team and the Navy discussed options for the channel crossing. Major considerations included: impact on the environment, aesthetics, functional reliability, and preservation of the historical nature of this landmark. The selected solution was to install a new HDPE pipeline using horizontal directional drilling (HDD). The design called for drilling a 2000 ft long, 8-inch pilot hole across the Main Channel. The pilot hole would be 30 ft below the channel bottom, effectively preventing disturbance of the channel bottom. After the pilot hole was reamed and enlarged, a 20- inch HDPE pipe was pulled from Ford Island to the Shipyard. The use of HDD also preserved the historic features along the Ford Island waterfront.

The unprecedented length of the pull, and tracking the drilling head 80 ft below the ocean was especially challenging. The need to keep the Main Channel open ruled out the use of a large boat or barge to track the drill head as it crossed the channel. Instead, a tracking grid system installed by divers on the sea floor was used to monitor the position and depth of the drill head.

The new force main had to cross under the transport system used for moving the 500-ton Shipyard cranes. The challenge was to minimize down-time of the cranes, which were critical for shipyard operations. The Navy, design team and Contractor worked closely together to come up with an effective solution, after it was discovered that the foundations deviated from details shown on record drawings.

Maintaining wastewater service on Ford Island during construction was a major goal for the project. An innovative sewage bypass plan was conceived that included highcapacity, low head pumps to convey flows from the collection system into a portable wet well, and a second set of high head pumps to pump the wastewater into the existing force main across the channel.