Bud and Cindy Johnstone worried that something like this would happen once a developer started clearing land above their Nu'uanu Valley home for a proposed subdivision. Yesterday, their fears were realized.

A boulder the size of a large Pilates exercise ball came tumbling down a steep hillside, slamming into the back of their home at 3429 Kahawalu Drive yesterday afternoon.

No one was injured when the boulder, an estimated 28 inches in diameter, struck the Johnstones' home at about 2:45 p.m., but the large rock crushed a shelf, blew a toolshed door off its hinges and caused other structural damage to the home.

Bud Johnstone was on the lanai about 20 feet away from the impact area when it hit and he said it "scared the hell out of me." He said he had been working with plants at the shelf about 15 minutes before the boulder came crashing down.

"I was in the lanai area, and all of a sudden I heard this huge crash and I saw the shutters in the bedroom pop back out. I came out and saw this boulder," Johnstone said.

He said he did not hear the boulder as it came rolling down the hillside, although he pointed to several large divots in his back lawn where the rock bounced and the muddy skid mark on the wall just outside the master bedroom where the boulder came to rest.

Luckily, he said, his wife, Cindy, was running errands or she could have been in the bedroom or out in the yard when the rock came down.

For years, residents along that hillside have opposed plans to develop the area above their homes. Despite that, developer Patrick Shin several months ago began construction on the 45-acre parcel for his Dowsett Highlands subdivision.

Shin could not be reached for comment yesterday.

Members of the Nu'uanu Valley Association filed a lawsuit against Shin and the city, claiming the city failed to follow open-records laws in the permitting process and that the project did not undergo environmental assessment before being approved.

The residents feared that the project would cause safety risks, such as rockfalls and mudslides. Johnstone said yesterday's incident, although terrifying, came as no surprise.

"I didn't know what had happened but I kind of thought it might be a rock because we had raised the issue of developing back here," Johnstone said. "We thought it might happen and it did."

Johnstone said he was visited by a worker with the contractor soon after the boulder hit his home. But he said the man did not offer any help.

"One person came down and he said, 'Why are you getting upset?' I said, 'It could have killed somebody.' Then he said, 'It's an accident and people die in accidents all the time,' " Johnstone said.

He said the man also wanted to remove the large rock, but Johnstone refused to let him touch it. Johnstone said the worker denied that the construction had anything to do with the rock's fall.

"We haven't had any rockslide problem in the 35 years that we've been here, but as soon as the development starts, suddenly we have one come down. There's some relationship there," Johnstone said.

The construction work is being blamed for another incident on Kahawalu Drive, where a large tree fell and crushed a workshed/studio in the backyard of Dr. Gabriel Ma's home on New Year's Eve.

Ma said the grading work for the development reaches the back of his property and has undermined the ground beneath many trees. He said he's lived in the home since 1967 and has not had any problems until now.

"There's nothing to support the trees," Ma said.

Ma said Shin came by his home yesterday, but that Shin said the fallen tree wasn't caused by the construction. Ma said another tree is leaning dangerously and that a similar incident may occur.