The state is about to launch work at eight roadside sites on O'ahu to reduce the risk of rockfalls and help protect motorists in Kailua and Wahiawa, and through Kipapa Gulch on Kamehameha Highway.

The rockfall projects, which will cost $2.08 million in all, could begin in two weeks pending permits, and be completed by late summer, said Scott Ishikawa, spokesman for the state Department of Transportation.

Three sites are among the 10 considered at greatest risk for rockslides, including the biggest project: on Kalaniana'ole Highway opposite and just above Le Jardin Academy.

Prometheus Construction, which has experience with rockfall projects, will do all the work.

Prometheus will begin in Kailua and already has signs up to alert motorists. The work will require lane closures during weekdays, Ishikawa said.

The state will also address two other sites on the top-10 list, just before and after the Karsten Thot Bridge in Wahiawa, Ishikawa said.

When work on those three sites is done, the state will have worked on six of the 10 sites deemed most at risk of rockfall.

The new work doesn't compare in scale or cost to the more substantial sites already completed, like the $7.8 million grading at Castle Junction that shaved 18,000 truckloads of dirt from a crumbling hillside and was completed in December 2005.

But it will address a number of sites in a short time, areas that residents say have worsened in recent years.

Four of the sites are on Kalaniana'ole Highway in Kailua — three between Castle Junction and Kapa'a Quarry Road.

Kailua resident Chuck Prentiss said he was happy the work will begin because the mitigation will also protect Kawai Nui Marsh, where muddy runoff flows during wet weather.

"For me the marsh is the biggest problem because even a rain that won't affect the traffic will allow some of the sediment to go into the marsh," said Prentiss, a member of the Kailua Neighborhood Board. "It's been a problem for many, many years."

LOOMING THREATS

The threat of a major slide has also been a concern, and over the years the slides have been getting worse, he said.

But Michael Buck, a Waimanalo resident, said the state might be going overboard with the projects.

"It's a little heavy-handed, but again because of the legal issue when you make an improvement, you invite people to a certain place like a state park, or especially a highway, the burden of responsibility is really on health and safety."

On the bigger project in Kailua, the contractor will anchor netting to the hillside after cutting it back slightly, Ishikawa said. The other projects will get biodegradable mats embedded with grass seeds, erosion control mats or mulching, he said.

The remaining project sites are on Kalaniana'ole Highway near Old Kalaniana'ole Road outside Kailua, and two sites on Kamehameha Highway between Kipapa Gulch and Lanikuhana Avenue.

LOCATION A FACTOR

Even though the projects aren't all on the top 10 list, the state decided to include the others because it made economic sense, Ishikawa said.

"Since they're grouped together in one location, the decision was to take care of it all one time rather than go back and forth," he said.

Jyun Yamamoto, a member of the Wahiawa Neighborhood Board, said he's glad the state is finally fixing the problem near the bridge and at Kipapa Gulch. The gulch site has been a serious problem for 30 to 40 years and the only solution was to fix the fence every time it was knocked down by a slide.

Yamamoto said he wasn't aware that the slopes near the Karsten Thot Bridge were hazardous until the state did a study of the slide sites on O'ahu. But now that it has been identified, it should be fixed, he said.

"People don't look upon it as being a real danger ... but I wouldn't want to be the one under there when it comes down," he said.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.