Erosion inside the Howard Hanson Dam on the Green River could directly impact Issaquah by causing major traffic jams, disrupt businesses and cut off the city’s sewer system, said officials at an Oct. 27 meeting.
City of Issaquah Emergency Management Director Bret Heath and Emergency Coordinator Steve Campbell addressed the Council of the Whole on the flooding potential this coming winter and outlined the local threats residents and businesses face. But the city is also keeping a wary eye on the potential for flooding in the Green River valley, which flows through southern King County and passes through Auburn, Kent and Tukwila downstream.
While the river flows through an area several miles to the south, the city’s residents and workers are reliant on the network of highways, utilities and transportation networks that lace the Puget Sound region together.
“It may impact us,” Campbell said. “This affects, not just that valley, but the entire state.”
Tukwila Emergency Management Director Hillman Mitchell reviewed the condition of the dam, which now has a new reinforced grout curtain but still can’t handle more than 30 percent of its capacity. Extra water will be passed through to the Green, which Army Corps of Engineers says has a one-in-three chance of reaching flood stage this winter.
Hillman also reviewed the various efforts made to repair or mitigate potential flooding, which could cost billions and displace thousands of residents. At it’s worst, he said, the flooding would inundate an eight-mile wide area at depths of 3 to 24 feet.
“We’re expecting that we could see 27,000 to 30,000 could be displaced from their homes,” Hillman said.
He said the flooding could create a “cascading effect” throughout the region, impacting roads and utilities — such as gas and electricity lines that are connected to area bridges.
Hillman has been working since January with King County and the cities of Auburn, Kent, Tukwila, Renton and Seattle to form a joint response plan to deal with the flooding.
News of the threat seemed to take some by surprise, including Council President Maureen McCarry.
“We didn’t know our wastewater would be affected,” she said.
Heath later reassured the council that the city had received assurances that the Sammamish Plateau Water and Sewer District would continue to pump the sewage to Renton, even if the wastewater plant there was overwhelmed.
Prior to Mitchell’s nighmare scenarios, Campbell and Issaquah Communications Coordinator Autumn Monahan reviewed the Issaquah’s own damage assessment and lessons learned from last January’s flooding.
Damages of over $1 million were caused by the Issaquah and Tibbetts Creek running over their banks and cresting twice, much as had happened in 1990. Issaquah has experienced five major flood events in the last 50 years.
Campbell said the city has undertaken $10 million in major capital improvements to remedy flooding issues in the flood plain, upon which much of the city rests, including the replacement of nine major bridges on Issaquah Creek, East Fork Issaquah Creek and Tibbetts Creek, buttressing channels of Issaquah and Tibbetts Creek and purchasing flood-prone homes & vacant land in vulnerable areas.
FEMA awarded the city a Class 5 status rating for flood mitigation efforts, a designation which significantly brings down the price of flood insurance. Campbell strongly encouraged business owners to take advantage of the discounted insurance, noting that 219 residents and businesses applied for the assistance after Issaquah was declared a Federally Declared Disaster Area.
“We’ve got to tie in our business community as well as our residential community, knowing what they can do to prevent some of these things happening to their businesses,” he said.
The most expensive damage The most expensive damage was focused on the Gilman Square shopping center, one of Issaquah oldest commercial districts. Greybeard’s Gilman Antique Gallery was one of several businesses flooded by nearly a foot of water. Owner Noel Fosnaugh said volunteers and free sandbags helped, but couldn’t prevent water from seeping inside and severely damaging his merchandise and the interior of the business.
Now working from the Tuxedo’s Junction Antique Mall in Duvall Fosnaugh said losses from the flooding and the bad economy are forcing him to close his antique business for good.
“It was a complete disaster,” he said. “It pretty much cost me the business in the end.”
Fosnaugh said he did not have flood insurance.
