KAILUA — A $5.8 million rockfall stabilization project in Kailua will be substantially complete within weeks but workers still need an additional two months to complete realignment and landscaping of the adjacent highway, officials said.

Workers have finished installing a mesh curtain strung along the hillside near the entrance to Kailua, securing it with more than 900 bolts drilled 30 feet into volcanic rock, said Cliff Tillotson, vice president of Prometheus Construction.

The mesh net is just one component of the work designed to prevent rockfalls and landslides that have slid across busy Kailua Road during heavy rains in recent years. Other parts of the project include a wide rock catchment basin halfway up the hillside, pinning individual boulders in place and a concrete drainage ditch to divert water away from the rocks, Tillotson said.

"It's one of the most complex jobs we've worked on," Tillotson said. "We had to come up with a smorgasbord of solutions to deal with different conditions on the site."

The work, paid for by the state Transportation Department, is part of several ongoing or planned projects dealing with landslides near state highways, said DOT spokesman Scott Ishikawa.

Other big projects in the works include replacing a rock catchment fence damaged by a landslide near Waimea Bay earlier this year, and a project at Makapu'u aimed at preventing slides on the Sea Life Park side of the slope, Ishikawa said.

Unlike another rockfall project, on the Pali Highway at Castle Junction, the contractor in Kailua did not try to haul away large parts of the hillside. Instead, it worked to secure most rocks in their existing locations, in some cases bolting or tying down individual boulders, Tillotson said.

The company used special drills to anchor 30-foot-long bolts into the rock and then attach the wire mesh, which will keep rocks from moving, he said.

At the peak of the project, passing motorists could see three teams of workers moving up and down the hillside, Spiderman-like, on specially engineered contraptions that combined winches and pneumatically-powered drills the size of a small car.

"The geology of the area was real tricky," Tillotson said.

Once the hillside work is done, the contractors will spend several months realigning adjacent Kailua Road and landscaping the median strip. The landscaping will include old trees that were removed from the site during the construction and more than half a dozen new royal palm trees.

The area had been on the state's Top 10 list of most dangerous rockslide areas for several years, but the work became essential in the spring of 2006, when a series of landslides and falling boulders occurred during heavy rain.

Once the highway was realigned to use the median strip during construction, work proceeded with little traffic disruption, Ishikawa said.

"This was one of the least intrusive construction projects we've done in a while," he said.

Ishikawa said the state hopes to work by the end of the year on the replacement fence in Waimea and the second phase of the Makapu'u project, a new catchment fence on the Waimanalo side of the slope.

Meanwhile, the department is studying ways to address the No. 2 site on its list of dangerous places, a nearly sheer cliff above Kamehameha Highway on the Hale'iwa side of Waimea Falls park.

"Right now, we're trying to figure out ways to keep traffic moving when we do the work," Ishikawa said.

When a rockfall closed the highway on the other side of the Waimea River in 2000, engineers were able to build a temporary road across the beach. That option will not be possible for the new location, Ishikawa said.

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.