The rain-weakened hill that let loose tons of rock and mud outside the Pali Highway tunnels is now structurally sound, the state said. Last night, after clearing the debris, the state reopened the highway's two town-bound lanes.

Also, heavy rain contributed to the spill of an estimated 330,000 gallons of partially treated sewage at the Sand Island Wastewater Treatment Plant, the city said last night.

Most of the sewage emptied into Honolulu Harbor, the city said. The public should stay clear of the area.

A geologist and an assistant from Hirata & Associates Inc. climbed the muddy hillside next to the Pali tunnels yesterday. They moved around the remaining earth and rocks and concluded that all of the loosened debris had already fallen and the remaining material posed no immediate danger, said state Department of Transportation spokesman Scott Ishikawa.

"The water slowly built up below weathered or fractured rock and brought everything down," Ishikawa said. "Otherwise the slope is stable. He is convinced that if we don't have torrential rains, the hillside will hold up."

He said there is no need for more work to shore up the hill.

The geologist, who did not grant interviews, came out on an emergency basis to inspect only the damaged hillside. He did not look at nearby hills to see if they posed a threat, Ishikawa said.

TREES CUT DOWN

On the town-side of the Pali tunnels, nearly 75 workers from the state Department of Transportation and Tajiri Lumber rotated through 30 hours of shifts to fill four dozen dump truck loads of debris from the Pali Highway. They also cut down several dozen loosened pine trees that threatened to fall onto the road and rerouted the waterfall that triggered the slide to stop more mud from covering the highway.

They dug a trench about 75 yards long and installed sandbags to reroute the waterfall toward the town-side of the hill and push the water into a 30-degree, grassy trail that workers use to trim trees.

"We had a makeshift stream so we decided to make a makeshift" solution, Ishikawa said.

Workers also installed temporary, concrete barriers to keep mud from landing on the Pali.

"It's just basically rain water coming off of the mountain side, but it's bringing mud on the road and creating a dangerous and slick surface," Ishikawa said. "That has nothing to do with the integrity of the hill. But it's dangerous for people coming out of the tunnel."

The slide left a muddy scar on the side of the Pali about 100 feet long and 40 feet high.

State officials reopened the town-bound lanes of Pali Highway at 9:05 last night, allowing traffic to flow in both directions for the first time since Wednesday morning's mudslide. All lanes will be open this morning, Ishikawa said.

Morning traffic from Kailua was contraflowed onto the Kailua-bound lanes from 4 a.m. to noon. After that, the highway was open to Kailua-bound traffic.

More rain yesterday across the Islands, one day after the landslide, continued to disrupt people's routines. The rain helped cut power to about 3,000 O'ahu residents, triggered a second day of sewage spills on the Windward side and forced a cancellation of the state Board of Education meeting on Moloka'i when some members could not fly into the Friendly Isle.

DRIER WEATHER

At one point yesterday, the rain gauge at the Hawai'i Kai Golf Course recorded 4 inches of rain per hour.

In the back of Kamilo Nui Valley, the usual road that Judy Nii takes to her farm behind Mariners Cove was under water so she had to use a newly created emergency access route.

"The road was flooded out," Nii said. "The water is deep and it's running really fast."

Later in the day, the National Weather Service canceled flash flood watches for O'ahu, Kaua'i and Ni'ihau but left the watch in effect for the Big Island. While isolated scattered showers are still possible through the weekend, the National Weather Service said the threat of heavy rainfall has ended, except on the Big Island.

The weekend will be drier than the past two days, said Maureen Ballard, forecaster and meteorologist, but light winds out of the south will make the air humid and sticky.

At the Sand Island wastewater plant, the city said, primary treated wastewater spilled yesterday between 11:45 a.m. and 1:30 p.m.

Runoff from the rain triggered three other wastewater spills on O'ahu yesterday totaling about 20,000 gallons — including another one at the city's Kane'ohe Pretreatment Facility, where untreated wastewater also overflowed Wednesday.

"Several days of heavy rains not only saturate the earth, but leave our wastewater system vulnerable to being overwhelmed by additional runoff," said Ken Shimizu, deputy director of Environmental Services.

SMOOTH COMMUTE

Honolulu Mayor Mufi Hannemann said the city on Wednesday quickly got news to the public about how the afternoon commute was affected by the mudslide. Officials went to the Traffic Control Center and communicated directly with radio and TV stations about which buses were rerouted and to where.

They learned from the problems of the Oct. 15 islandwide blackout triggered by the earthquakes, Hannemann said.

"We were frustrated because we could have told people there was no tsunami threat," he said.

So he said he felt good about the state-city cooperation following the Pali mudslide.

The result during yesterday's morning rush hour was a smooth traffic flow that brought commuters into town quicker than usual, Hannemann said.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.