AUBURN, Wash. – The Army Corps of Engineers said yesterday that hurried repairs this summer at the Howard Hanson Dam have greatly lessened the chances the Green River will flood this winter.
The corps put the likelihood of flooding at 1-in-25, compared with previous estimates of a 1-in-4 chance a flood would inundate the heavily developed Green River Valley downstream. The corps has been working around the clock to prevent flooding, pumping tons of grout into the problem area, an abutment at the dam that was badly weakened by a torrential storm last winter.
Residents, businesses and local governments in the long, flat valley south of Seattle have been working feverishly to fortify their property and the levees along the winding river against a potentially catastrophic flood during the winter rainy season.
Col. Anthony Wright, the corps Seattle district commander, said he could safely accept more water behind the dam than he was comfortable with before.
But he noted that while the 1-in-25 chance seems like a big reduction in the danger, flooding is still much more likely than when the dam can operate at capacity – when there’s about a 1-in-140 chance of flooding.
In recent weeks, some 40 miles of levees have been raised with sandbags, evacuation routes and emergency warning systems have been set up, and residents have been urged to assemble ‘go kits’ – documents, medicine and other valuables they’ll need if forced to flee on short notice.
Friends and neighbors gathered at Bobby Kendall’s place on a recent weekend to help him build a 2-foot barrier of sandbags around his home just a few hundred feet from the river in this Seattle suburb.
‘My house is my biggest asset,’ Kendall said. ‘I don’t want it to wash away or get filled with mud.’
A similar effort is under way at a Boeing Co. facility, where workers put up an 8-foot-high floodwall. Managers of a nearby Starbucks roasting plant are in constant communication with federal disaster officials. Other efforts have ranged from homeowners installing one-way valves to prevent toilets backing up, to Boeing erecting the sandbag wall around its sprawling Space Center in nearby Kent.
The valley cities and King County have held scores of informational meetings, passed out hundreds of thousands of sandbags, posted extensive information on special Web sites and organized a ‘reverse 911’ system to automatically call or message residents if an emergency is declared.
Besides Boeing, the valley floor has miles of malls, warehouses, and businesses small and large, including Recreational Equipment Inc.’s headquarters and Starbucks’ regional roasting plant. Starbucks did not provide specifics about its flood-preparation plan and how it will protect its beans and employees, but said it is doing its best to ‘minimize impact to our supply chain and operations.’
The four major cities in the Green River Valley – Auburn, Kent, Renton and Tukwila – all face the threat of flooding. An estimated 25,000 to 30,000 people live in flood zones, but Hillman Mitchell, the emergency management director in Tukwila, points out that 200,000 to 300,000 work or shop in the valley each day.
‘The number of people who may have to move could be very large,’ he said.
Beyond the physical damage, planners are warning people and businesses to prepare to be displaced for three weeks or more.
If a deluge comes, it will be because nature found a way to thwart a half-century of flood prevention.
Earlier this year, an abutment to the dam on the upper reaches of the Green River was found to be seriously weakened after record January rains. To reduce the danger the abutment might fail, the Corps of Engineers, which operates the flood control dam 22 miles east in the Cascade foothills, immediately restricted the reservoir to about 30 percent of capacity, greatly reducing its ability to limit how much water is released downstream.
Wright had said earlier that to avoid further damage to the abutment, there was a 25 percent chance he might have to release enough water this winter to flood much of the valley.
‘The Corps of Engineers tells us to be prepared for inches to feet,’ says Capt. Kyle Ohashi of the fire department in Kent, which could see 8 feet or more of water in worst-case scenarios. ‘All we can do is assume the worst, prepare for it and hope it never gets to that point.’
Mamie Petersen remembers the pre-dam floods near the Auburn home she and husband Roy have shared for 59 years. She and her husband loaded up on free sandbags at a city park.
‘Let me tell you, that river is boss,’ she said.’
