'The News Tribune' Article Featuring Tacoma's Central Wastewater Treatment Plant Project

Event Date:
Tuesday, December 1, 2015 - 12:00pm

New Wall Eases Flooding Fears at Tacoma's Biggest Waste Treatment Plant

The News Tribune article by Stacia Glenn

View the Tacoma Floodwall Project Video here.

A link to the full article can be found here.

“The whole premises of this project started from the... fact that this is the single most critical component in the city’s infrastructure,” division manager Geoffrey Smyth said recently.

“We started looking at it from a long-term perspective on how to protect the plant.”

The answer was a $9 million flood wall that wraps 2,700 feet around the outside of the plant at 2201 Portland Ave. The wall is on the opposite side of the facility because studies showed the biggest flood threat would come from the Puyallup River flooding upstream and running through the Tideflats and into the plant on the nonriver side.

“It’s a regional asset, and if it fails, it will have significant regional impact with significant economic and environmental harm,” Mello said.

The treatment plant serves 80 percent of Tacoma and another 20,000 customers in Fife, Fircrest and unincorporated Pierce County. It treats about 30 million gallons each day. That number jumps to 130 million gallons a day during winter storms. If the plant was flooded, officials say, it would short out $9 million to $10 million worth of equipment and effectively shut down the facility for months.

That means millions of gallons of waste would flow into Commencement Bay and the Puyallup River, causing irreparable harm to the environment.

It also would hurt the economy, because business at the Port of Tacoma would be halted during the cleanup.

Officials considered building a levee around the plant but didn’t have enough property to build on. Poor soil conditions ruled out a concrete flood wall, which left builders with steel.

Along the wall are five floodgates, two of which are raised manually and three that are raised automatically by water pressure. One of the manual gates is over a railroad track.

The floodgates, designed by Houston-based FloodBreak, were the first and the highest in the western United States.

The plant has two pumps to ensure that wastewater doesn’t spill into the Puyallup River if surface water inside the plant begins to rise. In case of heavy rain, the surface water is pumped out below one of the floodgates.

“We’re basically creating an island, shutting off all utility from the outside area,” assistant division manager Eric Johnson said.

A major challenge to construction was driving sheet piles into the ground within 12 inches of 23 utilities, including a sanitary sewer line and a water pressure main.

The project was finished on schedule and under budget.

That, coupled with several unique construction components, helped the city and contractor IMCO General Construction win the Northwest Construction Consumer Council’s distinguished project award for a public project under $10 million."