The state public housing authority is kicking off a long-delayed $500,000 project this month to mitigate rockfall concerns above Palolo Homes.

The low-income housing development has had several close calls with large boulders over the last several years, including a rock about half as big as a car that rolled down a steep hillside in 2006 and came close to apartments, according to Dave Nakamura, executive director of nonprofit Mutual Housing Association of Hawai'i Inc., which owns Palolo Homes.

Mutual bought Palolo Homes in 2002, but the Hawai'i Public Housing Authority held onto the land under the development and so is responsible for making sure the rocky mountainside is safe.

Chad Taniguchi, executive director of the authority, said the state is working to hire a geotechnical consultant within the next three weeks who will survey rockfall hazards above Palolo Homes and try to determine the best course of action in securing the hillside.

Some $20,000 has been appropriated for designing a rockfall mitigation project. An additional $480,000 will cover construction.

Possible remedies could include constructing a fence behind apartments butted against the hillside, putting in a moat to catch any falling rocks, or manually removing boulders that pose a threat.

The design phase of the project will take three to four months.

Construction is expected to be done by the end of year.

Taniguchi said the project is a priority. He added there could be cost overruns during the work, in which case the state would have to figure out where more money for the project could come from.

The $500,000 for rockfall mitigation behind the 306-unit Palolo Homes was appropriated by the Legislature in July 2006, but staffing shortages stalled work. A civil engineering consultant was hired six months ago. But he never started because he told the authority the work would be better handled by a geotechnical engineer.

"One and a half years later is not good," Taniguchi said.

"We should have done it (the project) sooner."

That's a relief to Nakamura, who said residents have long been concerned about the possibilities of boulders coming down.

"We've been very frustrated," he said. "It's just taken a very long time."

Palolo Homes isn't the first affordable housing development to need rockfall mitigation work. Kalihi Valley Homes, which also butts up against a steep hillside, has a moat behind it to catch falling rocks.

It is still unclear whether the work will require Palolo Homes residents to vacate their apartments temporarily, as has been the case during some other rockfall mitigation efforts. And if they do have to leave, officials are not yet sure where residents would stay.

Reach Mary Vorsino at mvorsino@honoluluadvertiser.com.