ANCHORAGE, Alaska — A plan is under way to draw down millions of gallons of oil stored in two tanks near Mount Redoubt — the Alaska volcano that has had 18 major eruptions in the last two weeks but has been relatively quiet in recent days.

The volcano 100 miles southwest of Anchorage began erupting on March 22. Since then, it has produced numerous large explosions that have sent mud and rock cascading down its flanks. Some of that mud and debris has reached the Drift River Terminal, 22 miles away from the volcano.

That has led to concerns that the terminal, where more than 6 million gallons of oil is stored in two tanks, could be damaged and there could be a catastrophic oil spill that would damage Cook Inlet’s valuable fisheries.

The Coast Guard said again Thursday that a concrete-enhanced dike surrounding the 42-year-old, Chevron-operated terminal is doing a good job of protecting the tanks.

Plans now are under way to draw down some of the oil in the two tanks. The facility’s other five tanks are not in use.

On Saturday, a Tesoro tanker will be brought to a platform near the terminal to remove some of the oil. The plan is to leave nearly 1.7 million gallons in each tank. Some oil needs to remain in the tanks to prevent them from becoming buoyant and floating away if there was a flood, according to the Coast Guard and officials with the Cook Inlet Pipeline Co. The tanks now are each holding 3.1 million gallons.

The tanker also will be taking on oil from two other facilities that feed Cook Inlet oil to then refill the terminal’s two tanks to the current levels through a 20-inch pipe. With the shutdown of the Drift River Terminal, those facilities are either critically short of oil storage capacity or are fast approaching it, said Capt. Mark Hamilton, the Coast Guard’s federal on-scene coordinator.

The oil also needs to begin flowing again as it is an important component of the Cook Inlet economy, he said.

“We are looking to remove as much of the product as we safely can,” Hamilton said.

During the transfer of oil, Hamilton said the risk that exists now at the facility will not be increased. That means that oil in the two tanks will not increase over its current level of 3.1 million gallons each.

The goal is to remove about 6.2 million gallons from the system.

The pipeline that runs from the terminal to the offshore platform is being tested in preparation for Saturday, Hamilton said. When the oil is off-loaded, it will be taken by tanker to a storage facility at the Tesoro refinery in Nikiski where the fairly light crude will be processed into gasoline and other petroleum products.

In the meantime, the Coast Guard, working with Cook Inlet Pipeline Co. and the state Department of Environmental Conservation, is working on a more long-range plan that will look into, among other things, how often a tanker will be needed at Drift River.

While it is encouraging that a plan is under way to draw down the level of oil in the tanks, it appears that the priority remains the same for the government and oil industry — to keep the oil flowing, said Bob Shavelson, executive director of conservation group Cook Inletkeeper.

One question does not get answered, Shavelson said: “What would it cost Cook Inlet to have a catastrophic spill?”