The community concern over a boulder perched above homes in Kalihi Valley in recent weeks served as a fresh reminder that Hawaii has a persistent problem because of its crumbling geological conditions.

But it’s really every day that Patrick Onishi remembers, waking up in the same Nuuanu home where his family was born and raised and, on one horrible morning almost 10 years ago, changed forever.

A boulder, perched unseen far above, came loose and tumbled downhill at 1:40 a.m. Aug. 9, 2002. It crashed into the back third of the house and took the life of the Onishis’ daughter, 26-year-old Dara Rei, who was soon to pursue a graduate degree at Columbia University.

In the years that followed, Onishi pursued legal remedies. A wrongful death suit brought a settlement among some parties; another lawsuit unsuccessfully sought an injunction to force the city to change its drainage system. The rainwater was funneled through a ditch on the side of Pacific Heights Road and through a pipe that emptied onto the hillside above the Onishis’ home. Erosion, the plaintiffs contended, eroded support for the boulder and set it loose.

"I had to look back on my naivete," said Onishi, now 67. "We purchased our home when I was 27 years old. The point is, as we’ve urbanized our city, we’ve ended up pushing our urban boundaries against the hillside."

To this day, elected officials have struggled to figure out a systematic way, rather than a reactive approach, to deal with the problem. In the Onishi case, neither the court actions nor the various attempts at legislative change ever yielded any new preventive programs. Lawmakers resolved to convene a task force to come up with solutions but never did so, Onishi said.

Still, he believes there’s been a distinct if low-profile government response to the tragedy within the agency that handles most of Honolulu’s residential development permits, the Department of Planning and Permitting. Onishi, still active as an architect, had directed the predecessor agency of DPP, the city Department of Land Utilization.

"They’re aware of the need to be much more vigilant about reviews and assessments about developments," he said.

Of course, the current DPP officials say there have been procedures on the books going back decades. The Land Use Ordinance requires the developer "to address the suitability of a site," in the course of getting various permits, such as for cluster housing and planned development housing, Jiro Sumada, deputy director of the department, said in an email response to a Star-Advertiser inquiry.

Developers would have to look at aspects including rockfall and other potentially harmful features and conditions of the site, he said.

"Similarly, our subdivision rules and regulations require developers to identify hazardous conditions and mitigate all of these conditions before a site is determined to be suitable for development," Sumada said.

"Each project is evaluated on a case-by-case basis. The project developer is required to assess the property and show the city that the site is suitable for development."

In addition, he said, more than 20 years ago the City Council identified higher-risk regions — Manoa, Palolo, Kuliouou, Moanalua and Aina Haina — where hillside development would require the property owner to do additional engineering studies in advance of receiving a building permit for a new structure; building permits for interior projects would not be held to this.

But risks are encountered all around the island — and throughout the state. The state Department of Land and Natural Resources maintains a special fund for resolving hazards such as rockfall zones. That’s the fund that was tapped for removal of the Kalihi boulder, located above the Kula Kolea Street area homes, said department spokeswoman Deborah Ward.

DLNR hasn’t conducted a comprehensive survey for risk zones on public land, she said, a project that would present practical challenges and expenses as immense as the state’s vast land holdings.

In 2001, however, the state Department of Transportation did a more limited evaluation of areas prone to landslides and rockfall along state highways on Oahu. It was driven in part by a March 2000 rockslide that blocked Kamehameha Highway near Waimea Bay, which ultimately led to the installation of "impact fences" and other measures to control hillside instability.

The result was the 2002 publication a roster of areas needing improvement (see map on page F5), ranked by priority so there could be a rational way of budgeting projects.

An update of the study, to include sites statewide, is due for completion near the end of this year, said DOT spokesman Derek Inoshita.

Another of the high-ranking sites was near Makapuu, and stabilizing that rockface was what brought Cliff Tillotson to Hawaii from his California home base. He never went back. Job after job came through for his employer, the rockfall mitigation firm Prometheus Construction, and Tillotson is now a Kaneohe resident working on various locations, most of them on Oahu.

Tillotson said his work now is distinct from what he did in California and other West Coast states because of location.

"It was almost all for CalTrans (the California Department of Transportation), and it was all dealing with public sites, not residential, like here," he said.

Further, he added, the islands’ basic geology gives Hawaii a uniquely worrisome situation, compared to other states. Volcanic flows left the islands fairly stratified, Tillotson said, with the slow-cooling lava layers forming the hard boulders and the porous surface rock creating what the experts call the "clinker zone."

The clinker rock erodes more quickly, he said, frequently exposing the boulders, which can become increasingly unstable over time.

Rockfalls have always been the result, Tillotson said, citing the earlier efforts to stem the slides by bolting chain link against the rock face of road cuts. The engineering of the solutions has improved, he said, but the real change that has raised the profile of rockfall cases is urbanization: Development has pushed residential areas against those crumbly valley walls.

The recent Kalihi case sparked a discussion among lawmakers about how to proceed. State Rep. John Mizuno, whose district includes those threatened Kula Kolea homes, said the Legislature may consider requiring insurance for private property owners that could cover the costs of mitigation, rather than having the state step in the public funds.

Onishi acknowledged that this may be part of the solution, but he’s concerned that it’s not proactive enough.

"Insurance is after the fact," he said. "The boulders are going to be life-threatening, and we want to be able to save a life."