Damage is estimated in the millions.

The release began Thursday night, just as many communities were beginning to recover from the two days of heavy rain and snowmelt that turned area rivers into raging torrents.

The Corps alerted King County Emergency Management officials Wednesday, but Pacific residents later said they weren’t warned that a possible flood was coming.

Once the floodwaters arrived, angry residents took aim at the Corps, which has operated the flood control dam on the White River east of Enumclaw since the 1940s.

Residents wanted to know why anyone would add water to a swollen river, and who’ll pay for the damage.

The Pacific flooding was upsetting, said Wayne Wagner, the Corps’ deputy chief for operations at the dam.

“It’s our mission to protect people and property,” he said, “and to have that happen is surprising and very embarrassing.”

Corps staff members said this week that they took the actions they usually do at the dam when a flood occurs.

During a similarly sized flood in 2006, the Corps released the same volume of water – 11,700 cubic feet per second – as the flooding began to recede. Water topped the levee in Pacific but flooding stayed in Pacific Park in the southeast part of town.

Not so this time.

“We have to review what we are doing,” Wagner said Monday. “Something has changed” in the river.

The change, he said, could be many things, from a lower carrying capacityby the White River because of sediment or gravel deposits, to a higher flow of water from the rainfall and small tributaries.

Or the water-saturated ground in the city might not have been able to absorb floodwater as readily as in the past.

Regardless of what the change turns out to be, Corps staff members say they know one thing: They can’t again release that high of a volume of water from the reservoir during a major flood.

Built in the 1940s, the dam controls floods in the lower White and Puyallup river valleys. The Corps also built levees on the lower Puyallup River. Together, the system helps protect the homes and businesses – including the Port of Tacoma – of about 400,000 people.

The dam controls about 40 percent of the Puyallup River system, and is meant to help prevent water from topping the levees in the Puyallup, Fife and Riverside areas.

Releasing water from the dam to deal with potential flooding is a balancing act, said Ken Brettmann, the Corps’ senior water manager who oversees control of the dam reservoir.

The idea is to hold water during a flood and then, after the flood, empty the reservoir to be ready for the next flood. The decision to begin emptying the reservoir is made only when the floodwaters finally begin to recede.

The decision last week followed the usual process, Brettmann said.

Before the storm that drenched the South Sound, the narrow, 5-mile-long reservoir behind the dam was empty.

But as rain and snowmelt poured into the reservoir, the Corps decided to close the dam’s outlets and not let more water flow into the White River, which empties into the Puyallup River in Puyallup.

The reservoir filled to 75 percent of capacity, or 260 feet of water. A full reservoir is 300 feet deep.

No water was let out during the record flooding, but when the flood peaked Thursday, officials began to release water from the reservoir into the White River.

Pierce and King counties were notified Thursday that the dam would begin emptying, Brettmann said.

The action was taken, in part, in preparation for another storm forecast to bring even more rain.

The reservoir could have held more water, he said, but the dam’s reservoir flood control managers working out of their Seattle center were worried about more heavy rain.

“At the time, we were looking at a pretty significant weather system hitting British Columbia over the weekend,” Brettmann said. “Should it change course and come down here, we were concerned that the reservoir pool was already 75 percent full.”

The worst-case scenario, he said, would be to have another storm hit when the reservoir was still nearly full. In the end, the system didn’t move south into the state.

Early Friday, Col. Anthony Wright, the district commander for the Corps’ Seattle district, was flying over the flood-prone areas and spotted the new flooding in Pacific. He called and asked whether the water released from the dam could be reduced.

Brettmann said the release was dropped to 9,700 cubic feet per second.

Overall, he said, the dam did its job for the Puyallup River.

Mike Archbold: 253-597-8692

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