HILO — Denise Rabuse watched waves crash Friday morning along Hakalau Beach Park’s rocky shoreline — one of her favorite spots on the island.
“I’ve just been enraptured with the beauty and energy down here,” said Rabuse, a visitor from Minnesota. “You can only experience it if you get down here.”
But Rabuse probably was among the last to visit the secluded Hamakua coastal spot for a while: the Hakalau Bridge — and neighboring Hakalau Beach Park — closed Friday and will remain closed to vehicle and pedestrian traffic until further notice.
The county Department of Public Works announced the closure Thursday. The one-lane, more than 100-year-old bridge is located in the gulch on Old Mamalahoa Highway. It is not the Highway 19 bridge.
DPW Director Frank DeMarco said the closure is the result of a mandate earlier this month from the Federal Highway Administration, funneled to the county through the state Department of Transportation.
A March 2016 underwater inspection showed rock and soil beneath the northern foundation of the bridge is being scoured away by the stream. The inspection report recommended an engineering evaluation of the observed scoured area, otherwise “the bridge could collapse during a heavy hurricane or storm or heavy traffic load.”
In October, a private engineering firm conducted a geotechnical assessment and concluded “it may be premature to consider closing the bridge.” This past January, a separate assessment concluded the bridge is structurally sound.
But DeMarco said the closure is ultimately a federal mandate as well as his own precautionary call — “for the protection of the public health.”
In the event of an earthquake for example, he said the bridge could lift, and “come down on weakened material.”
“You can’t predict where it might fail,” DeMarco said. “It’s the same dynamic as a house coming off its foundation, as the bridge lifts up and comes down it will damage the already weakened material.”
“From the (FHWA) perspective, there is a very real threat of failure of this bridge,” he added. “I also made the conclusion that, being this is a seismically active island, there certainly exists the potential for an earthquake.”
Repair work could involve strengthening the surrounding area of bridge foundation with concrete. DeMarco said that work is estimated to cost about $3 million — about 80 percent federally funding and 20 percent county funds to begin the design process. He said repair work is estimated to take about two years.
DPW spokesman Barett Otani said Friday the bridge and park could potentially reopen sooner, contingent on approval from the FHWA, which still has not reviewed the two privately conducted assessments that show a less urgent situation than the underwater assessment.
Email Kirsten Johnson at kjohnson@hawaiitribune-herald.com.
