Wednesday afternoon, AVO lowered the alert level to watch and the aviation color code to orange after seismicity decreased on the volcano about 75 miles northeast of Homer. A small explosion at 5:12 a.m. yesterday emitted some ash, but no ash was seen on radar for a second small explosion at 10:17 a.m. AVO continues monitoring Redoubt 24 hours a day and will change the alert level if necessary.

"This is going to be a wait-and-see game," said Christy Wallace, an AVO research geologist.

Although people in Kenai reported smelling sulfur on Monday, no ash was seen on the Kenai Peninsula from the recent explosions. Ash from 1/8- to 1/4-inch thick did fall Monday on Skwentna, Talkeetna and Cantwell as far as 250 miles away. Ash clouds caused flights into Anchorage International Airport to be canceled, with some Homer area passengers reported delayed including the Pee-Wee hockey team returning from a state tournament in Juneau.

Following a near-disaster during the last eruption cycle of Redoubt in December 1989 when a KLM Boeing 747 jet flew into an ash cloud, airlines have been extremely cautious about avoiding volcanic ash. Power noted that ash clouds can drift thousands of miles.

"It can impact communities in the Lower 48," he said.

The National Weather Service does daily wind-direction projections for varying altitudes. The National Ocean and Atmospheric Administration also does "puff ash" projections showing the spread of ash at varying times if Redoubt should blow. High-altitude ash is not likely to fall, with lower altitude ash of greater concern.

Links to both of these projections can be seen at the AVO site at www.avo.alaska.edu. That site also has advisories, images and other information about Redoubt and Alaska volcanoes. The National Weather Service issues ashfall advisories as needed.

Ash, debris and ice choked floods, or lahars, roaring down Drift River threatened the Cook Inlet Pipeline Company's Drift River Terminal, about 22 miles from the Redoubt summit. AVO scientists did an overflight Tuesday of the Drift River Terminal and valley.

Lahars covered a runway and ran up the side of a hangar, but did not breach an outside berm surrounding a seven-tank farm. No oil or oil sheen was seen. Muddy water did lap over the top of the outside berm. Ice the size of cars from the Drift Glacier littered the valley. Hundreds of fallen trees were seen in the valley and in Cook Inlet.

The lahar flood stripped off bark and branches 10 feet up the sides of mature trees. A muddy high-water mark of 20-25 feet also was seen.

"There was a huge flow of muddy water cascading down Drift Glacier," Wallace said.

The Drift River Terminal holds oil shipped in a pipeline from the Trading Bay Production Facility, which receives oil from Cook Inlet drilling platforms. Each of seven tanks can hold 3.108 million gallons of crude oil. Oil from the Drift River tanks is piped to a loading dock in Cook Inlet.

Each Drift River tank also has a second berm surrounding it. Two of the tanks have oil, with approximately 6.216 million gallons total of crude in both tanks, or about half the size of the 1989 Exxon Valdez oil spill.

The terminal is operated by Chevron Pipe Line Company. Cook Inlet Pipeline shut down the Drift River Terminal on Monday and evacuated 11 people during a lull in the eruption.

"The safety of our employees and our community is our top priority, and we have been coordinating with the U.S. Coast Guard, the Environmental Protection Agency and the Alaska Department of Environmental Conservation to prepare for this event," said Rod Flicken, Cook Inlet Pipe Line Company vice president.

Engineers flew in Tuesday to inspect the terminal and did not see any structural failure of the containment berms, said U.S. Coast Guard Petty Officer Sara Francis. More surveys were planned for Wednesday.

Cook Inletkeeper, the Homer environmental watchdog group, on Tuesday called for Chevron to draw-down its oil tanks.

"Now it's time for Chevron and the responsible state and federal agencies to safeguard Cook Inlet fisheries and the families and businesses they support, and to get the oil out of the terminal in a safe and responsible manner," said Inletkeeper executive director Bob Shavelson.

Inletkeeper had previously asked Chevron to publicly divulge the amount of oil in the Drift River tanks.

Francis said the U.S. Coast Guard gets daily reports of volume amounts as well as tanker off-loadings at Drift River. Oil from Trading Bay is being stored there temporarily, but if those tanks fill, Trading Bay might have to shut down, Francis said.

A decision to move the oil from Drift River would be made cooperatively by the Coast Guard, DEC and Chevron.

Cook Inlet Spill Prevention and Response has skimmers, boom and vessels standing by at Nikiski, Francis said. As of Wednesday morning, the Nikiski side of Cook Inlet was ice free.

The Coast Guard has not assessed the worst-case scenario of what would happen if oil spilled from Drift River, Francis said.

"Certainly it would have significant negative impacts," she said.

Oil spill response works best in calm waters. How well a response would be in ice or debris-filled waters is unknown.

AVO and other agencies also have not done a detailed hazards assessment from a Redoubt eruption on the Drift River Terminal, said Stephanie Prejean, a U.S. Geological Survey geophysicist with AVO. How lahars could affect the terminal is a question for Chevron.

"We can understand what's going on at the volcano," Prejean said. "They understand the engineering."

Redoubt began its latest phase late last Friday. Seismographs on or near Redoubt showed an increase in discrete seismic events, with up to 26 events per 10-minute period. The concern levels went up to warning and red late Sunday.

Unlike the first eruption in 1989, when Redoubt quickly went from increased seismic quakes to an eruption within days, this phase has been more drawn out. Scientists expect Redoubt to go through periods of dome building, when magma moves up from below the earth to the surface, collapsing of the dome and explosions with steam, gas and ash. Redoubt went through 20 such periods in 1989-90.

"The domes ooze out of the earth like toothpaste," Prejean said. "It's not a lava flow Hawaiian style," she added.

A big unknown is how much magma has been moving up toward the surface. Because Redoubt has so much ice, it's difficult to place GPS survey stations to detect subtle changes in upwelling of the ground.

"What we don't know is how much magma is driving this. It could go quickly or persist for months," Prejean said.

Michael Armstrong can be reached at michaelarmstrong.@homernews.com.