Roadway collapse in Hauula prompts emergency shoreline repairs

Erosion has taken out another chunk of Hawaii’s highways, forcing the state to schedule emergency repairs beginning today along Oahu’s Windward side.

The Hawaii Department of Transportation said Saturday that repairs to a 270-foot section of undermined shoulder along Kamehameha Highway will be done from 7 a.m. to 6:30 p.m., every day through Friday. The repairs are needed on the makai shoulder of the roadway, north of Pokiwai Bridge in Hauula.

Ed Sniffen, DOT deputy director for highways, said coastal erosion is impacting about 10% of the state’s 2,500 lane miles, mostly on Oahu. He said there are other serious areas of concern along Honoapiilani Highway in West Maui and on Kauai.

He said the state is trying to be proactive rather than reactive to the problem of coastal erosion, but there is a lot of catching up to do. Wave energy in the water creates one challenge for the state in protecting the state’s roadways along Windward Oahu, he said.

While a solid barrier could block waves from reaching the road, the construction could disrupt traffic and the wall itself, being inflexible, could repel waves and cause wrap-around erosion that affects nearby areas.

Instead, engineers are focusing on building smarter barriers made of boulders and loose fill held in place by concrete mix that allows the wave energy to dissipate upon impact.

“It’s kind of a cheap and effective fix, but it’s really only a short-term fix,” Sniffen said.

Since the loose fill repairs are only expected to last about five to 10 years, the state also is working with researchers at the University of Hawaii to come up with solutions that could last 10 to 25 years, and for the next tier, for 25 to 100 years.

Beaches in Hauula have shrunk at a “moderate” rate, according to the University of Hawaii’s School of Ocean and Earth Science and Technology’s coastal erosion website. Erosion was more serious in the northern and southern parts of Hauula, the study said.

Chronic erosion wiped out the beach at Kaipapau Point in the north and along Kamehameha Highway heading Kaneohe-bound to Kalaipaloa Point in the south, a stretch that includes the area of recent damage. In the 1990s, erosion claimed a pavilion at Hauula Beach Park, the study added.

Last April, erosion damaged part of Kamehameha Highway in Hauula, just south of Pokiwai Bridge near Hulahula Place. Crews fixed the damage by building up the area with concrete mix, then repaving the highway at a cost of $85,000.

The most recent damage was reported Friday, forcing DOT to close the makai lane of Kameha­meha Highway north of Pokiwai Bridge. Traffic was contraflowed through the area in both directions.

Officials found a 12-foot-long stretch of the shoulder and part of the lane had collapsed into the ocean. The road is about 6 feet above the beach.

An inspection revealed the shoulder was undercut about 20 feet in both directions from the fallen area.

DOT said the makai lane will be closed and traffic in both directions will be contraflowed while crews work on repairs. The makai lane will be reopened after working hours.

SNIFFEN estimated repairs will cost about $120,000, based on past similar work. He said the state also will look at additional areas also weakened by erosion from Kaneohe to Kaaawa and will try to complete similar repairs at the same time, using boulders, loose fill, and a concrete mix.

In Hauula, the DOT contacted other regulating agencies because the area to be repaired connects with a waterway, and DOT officials plan to follow processes to protect environmental and cultural resources.

Crews will repair the shoulder by laying filter fabric, then filling in the undermined area with cobblestones, topping the cobble with a cement mix, and repaving the highway.

DOT said previously scheduled work in Hauula at Hulahula Place and Kaipapau Loop will be canceled because of the emergency repairs.