Fearing a catastrophic dam break, state and Hawai'i county officials drained two 50-million gallon reservoirs above Waimea yesterday after inspectors determined they were unsafe after Sunday's earthquakes.

"We will never know how close we came to a major disaster," said Lanny Nakano, Hawai'i County assistant civil defense administrator.

"This is the force of Mother Nature."

Waikoloa Reservoirs 1 and 2, which hold drinking water for Waimea and surrounding communities, are expected to be empty by this afternoon.

Officials started draining them on Friday night, sending torrents of water into two formerly dry streambeds. By 6 p.m. yesterday, about 19 million gallons of water had been drained from Waikoloa Reservoir 1.

About 30 million gallons had yet to be drained.

The second reservoir still held about 34 million gallons at about 6 last night, and had already lost 21.5 million gallons.

Nakano said officials noticed water leaking out of holes on the earthen walls of the reservoirs on Friday night. Reservoir 1 had three so-called "boils," or 2- to 3-inch-diameter holes, while Reservoir 2 had two boils.

Though no evacuations were ordered yesterday, residents and business owners in Waimea were put on alert.

"It was very uneasy for a while," said Wayne Gocke, who lives in Waimea and closely watched the reservoirs with his neighbors yesterday.

Police and firefighters were stationed in Waimea until about 12:40 p.m. yesterday, when officials determined there was no longer an immediate threat.

The situation comes as aftershocks are still being felt on the Big Island and federal and state officials continue to gather damage reports and tally estimates from last Sunday's back-to-back major earthquakes.

About 4:30 a.m. yesterday, a 3.4-magnitude aftershock was centered eight miles off Kailua on the Big Island, according to the U.S. Geological Survey. It was one of six small temblors off the state yesterday.

Also yesterday, Maui Civil Defense officials closed Pa'ahi Bridge, about seven miles south of Hana, after it was deemed unsafe. The bridge suffered structural damage during the earthquakes and is closed until further notice.

ENOUGH DRINKING WATER

The drainage of the Waikoloa reservoirs means there is only one remaining reservoir to provide drinking water to Waimea, said state Civil Defense Vice Director Ed Teixeira. The Hawai'i County Department of Water Supply said yesterday the remaining reservoir will provide enough water for the town.

There are also at least two private water wells near Waimea, which could also feed drinking water to the community, Teixeira said.

The three Waikoloa reservoirs are owned by the Big Island Department of Water Supply. The two drained yesterday were built in the 1970s, and have earthen dams that are about 35 feet tall, a state inspection report shows.

The third is 21 years old.

State inspections conducted in April dubbed the three reservoirs "high hazard" because of the potential loss of life and economic impacts if a dam breach were to occur, not because of the conditions of the facilities.

In the inspections, state and federal engineers noted some minor seepage at Waikoloa Reservoir 1. But overall, the engineers determined the reservoirs were in good condition, and posed no safety hazards.

Teixeira said the reservoirs were inspected from the ground and by air on the day of the earthquakes last week, and again Monday.

Officials found no problems in those inspections.

But Friday, the state Department of Land and Natural Resources checked the reservoirs again and found the seepage points.

Initially, officials had planned to empty the reservoirs only enough to stop the leaking. But the decision was made yesterday afternoon to drain the reservoirs completely to do more extensive repairs.

'NO IMMEDIATE THREAT'

"There really was no immediate threat," Teixeira said. "It was a controlled drain. All the protective measures were taken."

The water from one reservoir was drained into Waiaka Stream, a normally dry streambed cutting through Waimea. The second reservoir was drained into the Waikoloa Stream, also a normally dry streambed.

Though the Big Island Water Department has assured residents there will be enough water for Waimea, some Big Island farmers worry the loss of the reservoirs could spur a ripple effect that cuts into their water supply.

Lorie Farrell, administrator of the Big Island Farm Bureau, said the earthquakes already have cut off some reservoirs to farmers.

Though the Waikoloa reservoirs aren't used by farmers, some private wells in the community are, she said. And if those wells are used for drinking water, some farmers could be without water or be forced to cut back.

Reach Mary Vorsino at mvorsino@honoluluadvertiser.com.