Bob Cowee eyes with confidence the 6-foot high flood wall that surrounds the Continental Mills office near the Green River in Tukwila to protect the property from flooding.
Cowee, director of engineering manufacturing for the company, oversaw the installation of the Hesco barrier, a wire mesh container filled with stones, gravel and sand. The company installed the barrier last year in case the Howard Hanson Dam failed to control the Green River from flooding.
No heavy rainstorms caused flooding last year. But the threat remains for a second consecutive winter as the U.S. Army Corps of Engineers still cannot operate the dam at full capacity as crews continue to repair the damaged abutment next to the dam.
“We heard the warning last year to get ready so we did,” said Cowee as he walked around the barrier at the two-story building at 18125 Andover Park West that sits west of the Green River and just south of South 180th Street. “No rain came, but we made the decision to keep our posture. Now that’s a good thing because forecasters are calling for above average rainfall because of La Nina.”
La Nina weather systems occur when the temperatures of the Pacific Ocean near the equator are colder than normal, which could mean more rain and snow.
The corps has lowered the threat of Green River flooding this winter to 1 in 60 from 1 in 33 last year because of installation of a grout curtain last year that stood up to summer tests to allow for more storage capacity in the reservoir behind the dam.
“We’ve made progress but there is still work to do,” said Casondra Brewster, an Army Corps public affairs specialist in Seattle. “The grout curtain is performing as well or better than we expected.”
But the odds of flooding are 1 in 140 when the dam is fully operational. An additional $44 million in repairs, including more drains and the extension of the existing drainage tunnel to put the dam back at its top level, will not be completed until after this flood season.
“When it’s all said and done, it will be the end of 2012 before we are completely finished,” Brewster said of the repairs to be done in phases over the next year. “Then we will see how good everything is.”
Meanwhile, Continental Mills and other Tukwila businesses and property owners in the valley must go through another winter of uncertainty about flooding.
“We are getting back to readiness stage,” Cowee said.
Nearly 180 employees work at the headquarters of Continental Mills, which also has a second building across from its main structure.
Continental Mills, which started in 1932 in Seattle, manufactures dry mix products under several brand names, including Krusteaz and Ghirardelli. The company has manufacturing plants in Kent, Pendleton Ore., and Kentucky.
As far as the Hesco barrier around the company’s main office, the flood wall has several gaps to allow access to the building. In case of a flood warning, a contractor has been hired to install the rest of the barrier at a moment’s notice. A large pile of stone and gravel sits on the property in order to fill the barrier.
“We have the materials staged so it can be done within 12 hours,” Cowee said.
Cowee declined to reveal how much the flood wall cost the company. The business also owns flood insurance.
“It was expensive,” he said about the Hesco barrier. “But we wanted something that would be effective and we feel we came up with that.”
Cowee said several other businesses in the area checked out the Hesco barrier at Continental Mills and decided to install the same type of flood wall.
Continental Mills also has an evacuation plan in place.
“We’ll protect the building and then relocate to Kirkland,” Cowee said. “We can get up and running in an hour.”
Ken Behrens, president of Mitchell Moving and Storage, 18800 Southcenter Parkway, said his company didn’t take extra flood protection steps because of a 13-foot high Hesco barrier installed by King County along the banks of the Green River on the southern border of his property.
“We’re hoping that will be efficient,” Behrens said. “There was nothing we could do to make it any better.”
Behrens, Cowee and the rest of the Green River Valley property owners hope the flood walls and giant sandbags can come down once the corps finishes repairs at the dam.
The grout curtain helped control the problems with water storage behind the dam that were discovered by the corps when a 10-foot-wide depression formed on the embankment next to the dam after heavy rain in January 2009. The corps stored a record amount of water in the reservoir during that storm to prevent flooding.
The federal government built the rock-and earth-fill Hanson dam in 1961 to control major flooding in the Green River Valley. But the dam won’t be at the same strength for at least one more winter.
“Nothing was necessary last winter,” Behrens said about the flood protection measures. “Who knows what happens this year.”