It will cost an estimated $2 million to strip loose rocks and boulders off steep slopes above two sections of Pi'ilani Highway on Maui, and part of the highway around the southern slope of Haleakala likely will remain closed for about two months while the work is done, said Maui County Managing Director Keith Regan.

Some frustrated rural residents are urging the county to reopen that section of Pi'ilani Highway, after county workers set up concrete barricades Monday to block traffic between the Kaupo area and Kipahulu.

That half-mile section of highway has been officially closed since the Oct. 15 earthquakes, but a number of area residents and tourists had been using the road anyway. The county had set up signs announcing the closure, but the signs were repeatedly stolen, county officials said.

The new concrete barricades were set up at 'Alelele and Kalepa to finally block all traffic after heavy rains in east Maui dumped rocks and debris from the cliffs above the highway onto the road Saturday, said Lynn ArakiRegan, economic development coordinator for Maui county.

"They're not just pebbles, they are actual boulders that fell on the highway, and had there been pedestrian traffic, had there been cars on the highway, the boulders would have hit them," Araki-Regan said.

The concrete barricades prompted complaints from residents such as Linda Domen, proprietor of Kaupo Store. Domen said she was in Kahului on Monday when she learned the county had blocked the road.

Domen's daughter was at Hana High School, and the newly installed barricade meant the girl faced a four-hour journey around Haleakala to get home. After Domen complained, she said, a Maui civil defense official made arrangements to have the girl flown to Kahului so Domen could pick her up there.

Domen said county officials gave residents no notice that the barricades were going up. She also faulted the county for failing to do more to stabilize the cliffs above the road despite the well-known rockfall hazards in the area.

In 2004, Haleakala National Park ranger Suzanne E. Roberts was killed when a falling boulder struck her after she stopped to remove rocks in the roadway in the Ka'apahu section of the park, where Pi'ilani Highway meets Hana Highway.

"For them to put blockades up there and all of a sudden pretend that's it's this big emergency situation, it's a slap in our face," Domen said.

Regan said the rural road was built by the state many years ago and turned over to the county, and that it never met federal highway standards. The rockfall hazards were aggravated by the Oct. 15 earthquakes, which opened new fissures, loosened debris and "made it worse than had ever been."

"The area is unstable, these rocks will come down," he said. "It's not a matter of if, it's a matter of when, because rocks are gonna come down."

Domen said the county should install a locking gate to limit access to the roadway. With a locking gate, residents who are willing to sign liability waivers and drive at their own risk would still be able to use the road, she said.

Regan said the county is considering that possibility but said scaling work to begin clearing debris from the slopes is expected to start within two weeks. There is no way traffic can be allowed on the road while that work is under way, he said.

A consultant's study is expected in mid-December that will make clear what additional work may need to be done, Maui officials said.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.