The nearly 30,000 residents of the Green River Valley need to buy flood insurance and make plans to evacuate their homes or businesses this winter, because of the potential from floods, due to seepage problems at an abutment next to the Howard Hanson Dam.

That was the message Gov. Christine Gregoire drove home at a press conference Monday morning, along the shores of the Green River by the Riverbend Golf Course in Kent. Gregoire also said the state has taken steps to help find additional funds to combat flooding and to make plans to evacuate and temporarily house residents, if necessary.

King County Executive Kirk Triplett organized the press conference to spread the word about the potential for flooding, as well as what government agencies are doing to prepare for a flood and what residents can do.

“We are here to help prepare our citizens and businesses that live here for what could be a difficult winter,” Gregoire said. “We can’t stop the rain, but we can get prepared in case you get another 100-year flood.”

The problems with water storage behind the dam started when a 10-foot-wide depression formed on the embankment next to the dam after heavy rain in early January. The dam is about 20 miles east of Kent.

Flooding from the Green River could strike the cities of Kent, Auburn, Renton and Tukwila this winter because the U.S. Army Corps of Engineers will not be able to store as much water as normal behind the facility because of the damaged abutment. The federal government built the rock-and earth-fill Hanson dam in 1961 to control major flooding in the Green River Valley.

“They need to get flood insurance,” Gregoire said of what residents can do. “They need to make plans for their families so they know what to do if the water rises and so they know where to go. They have to have an emergency kit and supplies and move valuables from ground level up.”

Col. Anthony Wright, commander of the Seattle district of the Army Corps, said there is a one in three chance the river could overflow its levees this winter.

The Corps is spending $8.8 million to install a grout curtain by Nov. 1 as a temporary fix. But Wright said he did not know at this time how much the temporary fix will help reduce the risk of flooding.

“I’ll have a better idea by Nov. 1, but it’s too early to say what the (dam reservoir) capacity will increase to,” Wright said.

Corps officials plan to spend as much as $3 million to study whether a concrete cutoff wall would be the best permanent fix. Construction of a cutoff wall could start in 2011 and would cost in the hundreds of millions of dollars.

With a long-term fix several years away, city, county and state officials want the federal government to help fund levee repairs and pay for sandbags if a flood does strike.

“We are doing what we can as a state to be a good partner,” Gregoire said. “I sent a letter to the Army Corps of Engineers asking them as a precaution to provide us early materials and equipment to help improve the levees where they are too low and to provide us with sandbags if the emergency does occur.”

Gregoire issued a directive Monday to all state agencies to assist King County just as though the county already faced an emergency.

State agencies will work on plans with the county to provide temporary shelters during floods, to work with businesses on formulating plans for dealing with floods and to work to find evacuation routes along highways.

“The valley has grown to more than 30,000 people and is a major area for industry and for family, so it’s very important we do everything we can to ensure their safety and protection,” Gregoire said.

Gregoire continues to work with the state’s congressional delegation to help find short-term mitigation dollars as well as a long-term solution to the problems facing the dam.

County Councilwoman Julia Patterson, whose District 5 includes most of Kent, said she appreciated the support of the governor and the city officials.

“A flood doesn’t know or care about boundaries, where one jurisdiction ends and another begins,” Patterson said at the press conference. “It will affect each and every one of us who lives, works and relies on the Green River Valley. That’s why it’s so important that all of us — King County, the King County Flood Control District, the valley cities, the U.S. Army Corp of Engineers, and the state, take a collective, proactive response to prepare.”

County officials estimate as many as 4,500 residents would need government-provided shelters if the valley needs to be evacuated. Triplett said potential shelter sites include Green River Community College, the Tacoma Dome and public schools. County officials have not yet finalized the evacuation routes and shelter plans.

Triplett said Monday he is sending three pieces of legislation to the King County Council this week to increase protection of people and businesses, their property, and county facilities and services in the event of a flood in the Green River Valley. He will request approximately $40 million for 2009 flood-preparation costs.

Triplett will request $8.4 million to temporarily increase the height of Green River levees and for other items to increase flood-fighting capabilities. He plans to ask for another $32 million to plan and provide for continuity of regional services such as Superior Court, elections, animal control, wastewater treatment and public health.

That money would help protect county facilities such as the Norm Maleng Regional Justice Center in Kent and the South Wastewater Treatment Plant in Renton.

For more information, go to King County flood plans. Click on National Flood Insurance Program on the county site for property searches on flood risk and insurance rates.