Hawaii’s Longest Suspension Bridge at Kapalua Ziplines, Maui
The Kapalua Bridge soars over Kaopala Gulch in the West Maui Mountains, 1,600 feet in elevation above the northwest Maui coastline. It is the most recent addition to Kapalua Resort’s renowned mountain adventure course, a world-class facility that includes many thousands of feet of ziplines. Spanning 360 feet, Kapalua Bridge is the longest suspension bridge in Hawaii.
During the wet winter season, one can look 120 feet down to where Kaopala Stream waters accumulate before vaulting off a rocky precipice and plummeting 80 more feet into the depths of the gulch. The sweeping view from the bridge deck of Molokai and Lanai Islands and the limitless expanse of ocean stretching to the horizon is breathtaking, especially at sunset.
Spectacular rainbows above, below, or surrounding the bridge are an almost daily event. Nearby, zipline travellers of every age and description soar through space, providing ample live entertainment. An expansive biological preserve sits uphill of the bridge site and boasts one of the most biodiverse regions in the islands.
It required three 40-foot shipping containers (well over 100,000 pounds in all) to transport all of the pre-fabricated bridge components and requisite tools from Seattle to Maui, and several trips with two flatbed trucks, a grade-all forklift, and two pickups to get it all up through the Maui Gold pineapple fields and onto the mountain.
During peak production Sahale had a crew of 9 excavating, building abutments, and assembling tower legs, and in all, it took seven weeks to build the bridge from start to finish.
The famous (and persistent) Pacific Trade Winds of 20-30 mph blew constantly, making rope work, rigging, and certain installation steps an interesting challenge. Anticipating even higher winds over the life of the structure, the Kapalua Bridge was designed with heavier components and internal sway bracing so that it can withstand hurricane-force winds exceeding 105 mph.
This bridge is the first Sahale bridge to include new construction lattice column towers and to have a three pipe (handrail, grab rail and kick rail, see right) handrail arrangement integrated with the cable railing system. The double mainline pairs are unusual but an effective redundant design first used in a Sahale suspension bridge in 1995 (Tawkes-Foster).
Lattice column towers are a throwback to steel fabrication practice in the late 19th and early 20th Century and were chosen by the owner to evoke a timeless appeal. There are many parts in a lattice column: The Kapalua Bridge towers are comprised of 1,656 lace bars and 3,600 fasteners. The concrete abutments are anchored with helical piles that go down to bedrock 45 to 65 feet deep, and the concrete-filled steel earth anchors are up to 18 feet deep.
The towers and superstructure are A 588 weathering steel and the decking is composed of lightweight slip-proof UVA-rated pultruded fiberglass grating. The mainlines, suspender cables, and under-deck diagonal cables are all galvanized structural strand or wire rope of Independent Wire Rope Core (IWRC) design.