Farmers and homeowners along Green Valley Road crammed into the lodge building at Flaming Geyser State Park last week to hear about possible flooding of the Green River this fall and winter owing to the compromised holding capacity of the Howard Hanson dam.

They also got the latest on what the county, state and federal government is doing and picked up tips for helping themselves, their animals and their property.

Col. James Rollins, deputy commander of the Seattle District of the Army Corps of Engineers, described how last January’s storm raised the water behind the dam to record levels, put unprecedented stress on the structure and opened up two holes in the dam’s right abutment, a natural support made of 20,000-year-old landslide material.

Engineers soon noticed abnormally high seepage rates in the drainage tunnels that run underneath the embankment downstream. While some seepage through the abutment is expected, this water carried dirt and rocks, the basic structural components of the embankment. The loss of this material could undermine the structural integrity of the abutment itself.

“It makes us very nervous,” Rollins said.

The upshot is that engineers have lost some confidence in the holding capacity of the 48-year-old dam.

Last summer the Corps hired two contractors to work on projects aimed at improving the integrity of the abutment and putting the dam in a good position for flood season. The first contractor is drilling holes in the abutment to a depth between 90 and 160 feet and filling them with a cement mixture called grout. Rollins said the idea is to create a seepage barrier that will at least slow the water to acceptable levels. The second contractor is drilling “relief wells” in the drainage tunnels, wells that will collect seepage and draw it out at a controllable rate. These temporary repairs are scheduled to be completed by Nov. 1.

Rollins said these repairs, coupled with levee projects downstream and other measures, should put the Corps in the best position to help reduce, but not eliminate, the risk of flooding this rainy season.

Corps District Commander Anthony Wright recently estimated the chance of flooding at one in three.

Rollins said if the water behind the dam rises too high, engineers would have to release some to protect the integrity of the dam itself, causing flooding downstream. A more permanent solution in the form of a multi-million dollar barrier wall is at least three to five years off, but Rollins said that everything possible is being done to speed things along.

He urged residents to buy flood insurance.

“Even if you don’t see your house necessarily covered by one of those colors on the inundation maps, buy flood insurance,” Rollins said.

Robin Friedman, director of King County’s Office of Emergency Management, said his staff will monitor weather systems in conjunction with the Corps and with King County’s Flood Warning Center to make sure everybody has the latest information on rainfall, knows how the dam is operating and is aware of all the circumstances that might require evacuation. He said a duty officer will be gathering information from a variety of sources around the clock.

Friedman said the county would probably decide whether to evacuate based on weather outlooks. He said it will take a little more time to move things from agricultural areas like Green Valley Road than just to drive away from a house.

“We haven’t nailed down 100 percent what the circumstances would be that would cause us to tell you to evacuate,” Friedman said. “We think that 24 to 48 hours out we are going to have a pretty good idea what the weather is going to look like.”

Friedman stressed the importance of personal preparation, including having a ready-to-go kit handy should the need arise to move immediately. He urged people to get a NOAA radio, a useful device that turns itself on in an emergency. He said residents should follow news reports and be on the lookout for alerts from the National Weather Service, the King County Office of Emergency Management and the King County Sheriff’s Office.

Friedman said there are 288 shelter locations now, but the problem is selecting them and making them big enough.

“Right now, we have five potential mega shelter locations. We’re looking at things like the Tacoma Dome, we’re looking at things like warehouses and warehouse spaces. We’re talking with the Red Cross about bringing in national level resources if we need to shelter at those locations. If the event happened today, I could find shelter for everybody that needed to be sheltered. The problem is we want to do it more effectively,” Friedman said.

Gretchen McCallum, president of the non-profit Washington State Animal Response Team (WSART) said her organization trains its volunteers to evacuate and shelter animals, livestock and pets in disasters and emergencies. All members are credentialed as emergency workers in the state and work closely with the King County Office of Emergency Management. She WSART will staff an emergency livestock shelter in event of flooding valley, 24 hours a day, seven days a week.

“I must stress that the prime mover in evacuating your animals is you. You must be planning now to get them out,” McCallum said.

Van Strong, a Snoqualmie Valley farmer with 40 years of experience dealing with flooding, advised Green Valley Road residents to make an inventory of their farm equipment before the event so they would know where everything was afterward.

“You are really going to need these things after the flood, because the worst part is cleaning up after the mess has been made. You can’t move your equipment around when you are wading through three feet of water, you can’t put your generators up, you can’t take care of your waste oil, your gas cans. If your house goes under, you can’t believe the silt and the muck that is just everywhere. It’s just an unbelievable mess to clean up,” Strong said.

Strong said he had built “critter pads,” pads of dirt up to 10 feet or more high to keep livestock away from floodwaters. When residents learned it was too late to obtain a permit in King County in time for the flood season, tempers boiled over.

One man castigated officials for moving too slowly.

“It’s obvious you folks don’t live in the Green Valley,” the man snapped. “Why is it that people who live rurally always have to sacrifice for people that live in the city? You’re not taking our concerns to your office and really getting the job done. You’ve got no plans for us, how are we supposed to sit here and take that?”

“Everyone up here is working their butts off, trying to figure out answers to this,” responded Mamie Brower, Corps Program Manager for the Howard Hanson Dam.