A city crew attempted to stabilize debris from a collapsed retaining rock wall, 8 to 9 decades old, along Diamond Head Road on Tuesday afternoon and to clear the roadway.
A heavy equipment operator removed some trees, wood, metal and rubble from the rock wall, which sat precariously along the bottom of a nearly vertical hillside across from Makalei Beach Park near Kapiolani Park.
Less than a minute into the work, a plumeria tree and a chunk of the remaining wall came crashing down.
"It’s going to come; it’s just a matter of when," said John Nigro, road labor supervisor for the city’s Department of Facilities Management’s Road Division.
Police got the call at 1:42 p.m. and shut down Diamond Head Road between Coconut Avenue and the Diamond Head Lighthouse in both directions at 3:25 p.m. The road was reopened at 9:16 p.m.
The section of Diamond Head Road is well used by motorists as a shortcut into Waikiki from Kahala, and others taking the scenic drive along the coast around Diamond Head.
Runners, walkers, bicyclists, surfers and other beachgoers got through until the removal work began, and many took a detour along the beach.
Nigro said the city will bill the owner of the wall and house above Diamond Head Road at 2911 Makalei Place. The owner was traveling in Cuba, according to a relative, and had not yet been reached late Tuesday afternoon.
Nigro said he didn’t know the cause of the collapse.
The wall is believed to have been built in the 1920s, Nigro said, and apparently without rebar.
Kelsey Noetzelmann, 24, who lives across the street from the wall, was working out in the park and witnessed the collapse.
"I heard like a few cracks, like it sounded kind of like thunder, and I turned around and the wall just started falling down," she said. "It fell onto the power lines and kind of bounced back, and everything fell to the ground.
"Luckily there was like no cars underneath it or anything like that."
Noetzelmann called police and, until they arrived, helped direct traffic along with a construction worker.
Victoria Mathieu, who also lives across the street, was asleep at the time.
"I’m just so glad nobody got hurt," she said. "You just figure it’s safe and nothing would tell you otherwise."
Mathieu and other neighbors speculated that the recent heavy rain contributed to the wall’s collapse and that the water had built up behind the wall.
Bicyclist Dennis Chapman, 49, observed how dry Diamond Head had been a few years ago, and noted how kiawe trees had taken over the hillside and that their roots may have weakened the wall.
