On a sunny fall Saturday, friends and neighbors gathered at Bobby Kendall's place to help him build a 2-foot barrier of sandbags around his suburban Seattle home. Such get-togethers have become a familiar ritual on the block in recent weeks as people lend a hand to neighbors to barricade homes.

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.

It is all part of a feverish effort to fortify the heavily developed Green River Valley against a potentially catastrophic flood during the winter rainy season.

Engineers have said there is a 1-in-4 chance that a flood will inundate the valley. The U.S. Army Corps of Engineers has been working around the clock to prevent flooding, namely by pumping tons of grout into the problem area _ a dam abutment that was found badly weakened by a torrential storm last winter.

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.

"My house is my biggest asset," Kendall said. "I don't want it to wash away or get filled with mud."

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. Boeing also is barricading its costly aircraft flight simulators in Renton.

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.

And beyond the physical damage, planners are warning people and businesses to prepare to be displaced for three weeks or more.

Boeing spokesman Bill Cogswell said the 3- to 4-mile barrier around the Kent complex is necessary insurance to protect about 3,000 employees, a data center and the plant's valuable defense work. Boeing is putting its valuables on higher floors, moving equipment out and planning which of its other Seattle-area facilities can take over if water reaches the plant or more likely, blocks valley roads.

"Our aim is to insure the safety of our employees, to make sure we minimize the potential business impact and that everyone knows where to go and what to do in the event of a flood," he said.

If a deluge comes, it will be because nature found a way to thwart a half-century of flood prevention. Continued...