In the early morning of Dec. 7, 1941, the clear, quiet blue Hawaiian sky was pierced by the thunderous roar of hundreds of Japanese warplanes crossing over Oahu and descending toward Pearl Harbor. The sleeping American Pacific Fleet was set squarely in their crosshairs. The first wave of torpedo bombers had clear shots at the hulls of defenseless battleships and cruisers. A second wave of dive bombers targeted harbor air defenses: first at Hickam Field and Wheeler Air Force Base, then at smaller fields at Bellows and Ford Island. In 90 minutes, 12 warships were sunk, 188 planes were destroyed and more than 2000 people lost their lives.

Sixty-five years later, we still remember that “date which will live in infamy.” The U.S. military has taken great efforts to preserve this memory by creating monuments in and around Pearl Harbor. Historic Ford Island — the island located in the center of the harbor and one of the principal attack targets — is one such location. Although the historic airstrip on the island is no longer active, the base remains open. It is home to numerous military personnel and is open year-round to tourists visiting the USS Arizona and the USS Missouri memorials.

Recently, the U.S. Navy designated Ford Island a “showcase” military facility, setting plans in motion to build a state-of-the-art museum and residential housing. To serve the increased electric load associated with these improvements, the U.S. Navy has contracted Hawaiian Electric Co. (HECO; Honolulu, Hawaii, U.S.) to provide 40 MVA of capacity on the island with a new 46-kV/12-kV substation and two new 46-kV subtransmission circuits. The challenge for HECO was to install the 46-kV circuits across and below the 1-mile (1.6-km)-wide channel in Pearl Harbor.

HECO along with engineering consultant POWER Engineers Inc. (Hailey, Idaho, U.S.) conducted a study to assess the feasibility of various underground cable systems, including use patterns and reliability, maintenance requirements, economic feasibility and construction viability. After analyzing four different route options, HECO selected a “best transmission” option — the design of two 46-kV circuits from Kamehameha Highway in Halawa area (near Aloha Stadium) on Oahu to a new substation on Ford Island via two 5000-ft (1524-m) horizontal directional drills under Pearl Harbor.

The project was divided into two major phases: the ductbank underground installations on land at Halawa and Ford Island, and the directional-drill application for the underground circuits beneath the harbor. The ductbank designs called for the installation of two 46-kV underground circuits. Each circuit would be comprised of four 5-inch (127-mm) polyvinyl chloride (PVC) conduits for the electric cable (three conduits for each cross-linked polyethylene (XLPE) cable phase conductor and one spare), one 5-inch PVC conduit for fiber-optic and other inner ducts, and one 2-inch (51-mm) conduit for the ground wire. The underground circuits would be installed using open cut trenches and a concrete-encased ductbank on land.

The portion of the line beneath the harbor would be more difficult. The design called for two separate horizontal directional drills (one for each circuit), which would be conducted by a directional drilling contractor. The contractor would then pull in two separate 24-inch (610-mm) steel casings, each containing the conduit to house the complete circuit and associated cables. Each circuit would require four 6-inch (152-mm) HDPE SDR-11 conduits to accommodate the 46-kV XLPE 1750-kcmil cable (three phases and one spare), one 2-inch HDPE SDR-11 conduit for the ground wire, and one 5-inch HDPE SDR-11 for the communications fiber-optic cable and other inner ducts. Once installed, the two 5000-plus linear feet circuits would be among the longest dielectric cable lengths in the world.

The one-of-a-kind design was completed in November 2004 and the search for a contractor began in earnest. HECO released the request for proposals in early 2005 and awarded the contract to Hawaiian Dredging Construction Co. (HDCC; Oahu) and a team of subcontractors comprised of Laney Directional Drilling (Humble, Texas, U.S.), American Electric Inc. (AE; Honolulu), and other vendors and subcontractors. The notice to proceed for the project was granted on July 5, 2005, and construction started soon thereafter.

HECO and general contractor HDCC understood from the start that this project would require pitch-perfect planning, execution, and clear and constant communication because the Navy was protective of the historical importance of Ford Island. Areas such as bullet-riddled Runway 22 and high-security Navy locations on the island were off-limits to construction contractors. The Navy also made it clear that the construction schedule needed to be rigid to minimize disruption to the island's military residents.

The project was planned in concurrent phases to maximize efficiency and minimize disruption. The challenge, however, with concurrent phases was that the project would need to proceed as close to the planned schedule as possible to avoid costly delays. Another challenge was the limited space for set up and work implementation, both at Halawa and Ford Island. The major phases of the project included: planning and procurement; ductline; casing and conduit; horizontal directional drilling; and cable installation.

Everyone hit the ground running soon after the notice to proceed was granted. The procurement process needed to be initiated first, because the materials and equipment required for this type of project are not readily available in Hawaii. HDCC placed the order for the steel casing and began assembling and mobilizing construction teams and field equipment. Back in Humble, Texas, Laney began assessing the directional-drilling specifications to determine material and equipment requirements. Directional drilling requires a drilling rig, large quantities of bentonite (drilling fluid), mixing tanks, pumps, drill pipe, steel rollers, generators and other equipment, all of which had to be shipped to Hawaii.

AE, the project's electrical contractor, assessed the project design and submitted cable orders to Forte Power Systems, a division of Southwire, and placed orders for terminations and splices. They also placed particular emphasis on the cable pulling process. Because of the distance of the cable pull, they would need the right equipment and the right amount of lubrication. AE consulted with the Pull-Planner designer, American Polywater, to have the company verify AE's pulling calculations, given the architecture of the drill path (bends, dips and jog), the temperature of the conduit and other environmental factors. Based on this analysis, AE ordered “Polywater J” lubricant and pulling equipment to help during the high-profile cable pull — all to keep the calculated tension below 12,000 lbs (5443 kgs).

HDCC began work on the ductline, manholes and pull vaults on the Halawa side of the project. Excavation and trenching started on Richardson Field at Kamehameha Highway and progressed across the field and down the slope to Halawa Landing, directly adjacent to the USS Bowfin Submarine Museum and Park. The excavation and construction of the 700-linear-ft (213-m) concrete-encased ductbank took a little more than one month to complete.

The crews then mobilized to Ford Island. The entire Ford Island subsurface infrastructure and road system was being upgraded simultaneously, which meant there were numerous contractors on-site. Work was further complicated because of congestion (the line passes across a golf course, roads and parking lots) and existing island activity. After the ductline to the substation was finished, the land portion was complete and ready for cable installation.

Before Laney could begin drilling, HDCC had to assemble two 5000-ft-long, 24-inch steel casings and associated conduit. The original plan was to first assemble and pull in each steel casing, and then, once the casings were installed, assemble and pull the high-density polyethylene (HDPE) conduit. Due to space constraints, ongoing construction on the island and concerns that the HDPE pipe bundles would become twisted while being pulled into each casing, HDCC devised a better solution.

HDCC first fused the entire length of HDPE conduit, strapping each of them together with 0.75-inch (19-mm) steel straps to form a conduit bundle, which was anchored to a dead man on the western-most edge of the pipe-string staging area. Crews pulled 200- to 240-linear-ft (656 to 787 m) sections of steel casing — starting at the dead man end, removing and reattaching the bundle for each section of steel — over the HDPE conduit bundle using a WA 320 loader and plenty of Polywater J lubricant. Each casing was welded together piece by piece over the conduit bundle until the pipe string stretched the entire 5000 ft. The casings were supported on steel rollers to minimize friction during pulling.