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SPU’s plan to get Seattle out of deep sh*t

The steps on the scaffolding are steep and slippery in the rain. Slowly we navigate downward to an underground tank that will eventually hold 2 million gallons of raw sewage and polluted stormwater overflow to keep it from entering Lake Washington. Last year, more than 154 million gallons overflowed from city-owned pipes into all of the city’s dozen water bodies and, with it, 8,000 tons of toxic metals and volatile chemicals.

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Seattle is one of nearly 800 U.S. cities that uses a combined sewer system, which collects rainwater, industrial wastewater and raw sewage in one set of pipes. Built in times of smaller populations and less use, combined sewer systems often overflow during heavy rain or storms, shunting extra wastewater and sewage into nearby bodies of water.  

Here on Lake Washington, Seattle Public Utilities (SPU) is building the tank to stop the city’s highest frequency overflow. In 2012 pipes in the basin on the western flank of the lake — which includes View Ridge, U Village and Sand Point — overflowed 149 times.

A map, updated hourly, of sewer overflows in Northeast Seattle on January 14th, 2014. Photo: King County 

"Once the tank is used, we'll be able to operate and control this whole tank from back in our operations and control center down in Sodo," says Keith Ward, an engineer with Seattle Public Utilities. "And when the storm is over, we'll pump the combined sewage back up 65th, down Sandpoint Way and back into the system." 

Real time controls and underground pipes will carry the toxic overflow to King County’s treatment plant at Discovery Park.  

Roughly 20 feet deep, the tank has three vaults for odor control and massive amounts of electrical, instrumentation, controls and steel. Construction manager Dennis Davis of CDM Smith points to layers of rebar reinforcing the construction.

Lake Washington's Windermere Basin tank will hold 2 million gallons of wastewater when complete. Photo: SPU/ Susan Stoltzfus

"This is going to have a massive tipping bucket. This is what we're all waiting for — when they test this tipping bucket and it comes roaring down here and then washes this out," said Davis. The bucket, which was designed to work in both stormy and dry weather, will be filled with fresh water to clean out the holding tank. 

The tank can handle 2 million gallons of stormwater, but since an estimated 47 million gallons overflowed into Lake Washington last year, it may need to operate continuously during big storms. Those generally happen only two or three times a year.

"The idea is when there's a big storm, we fill up this tank. We let the storm go out, we pump it back into the system. If there's another big storm we fill up the tank," said Ward.

The Windermere Basin tank — which hasn’t been given a name just yet — will cost the city $50 million and will be just one of a larger system of tanks dealing with Seattle's stormwater runoff and pollution problem, which violates the Clean Water Act. Their construction comes on the heels of years of water quality and public health violations, penalties and compliance orders issued by state and federal regulators.

In 2012 alone, there were 355 overflow events in the city’s 12 receiving waters. One hundred forty nine of those were in Lake Washington. Salmon Bay had 96, which spilled some 59 million gallons of polluted stormwater and sewage. Several years ago, one Seward Park storm caused a million gallons of sewage and stormwater to overflow.

SPU began excavation on the Windermere Basin tank a few years ago to show good faith to regulators, says Ward. Since 2001, the agency has also been working to contain the stormwater problem with rain gardens, retrofits and green infrastructure.

Last year it signed a “Consent Decree” with the Environmental Protection Agency that sets deadlines to make more headway. "We're talking not usual enforcement cases, we're talking like superfund enforcement cases here," said Rob Grandinetti of the EPA. "When we're looking at the long-term period this is going to take, as well as the amount of money it's going to take to do it, then the consent decree is really the only mechanism."

Under the decree, the holding tank on Lake Washington must be completed by 2015, but is expected to be up and running by November. Another tank near Genesee is slated to be completed in early 2015; Seward Park's is scheduled for 2017.

Polluted stormwater is a nationwide problem. New York suffers 27 billion gallons of overflow annually to Seattle's 200 million and EPA enforcement cases like Seattle's are underway in San Antonio, Miami, Boston and Pineville, Louisiana, among others. Each region’s challenge is different due to climate, rain fall and finances.

Solutions aren’t cheap. It’s not uncommon for superfund costs to be in the hundreds of millions of dollars, says Grandinetti, and while there are opportunities to fund cleanup with state money, it’s usually cities who are on the hook. When a smaller city doesn’t have the money, legal wrangling, citizen lawsuits and polluted waterways are the end result.

Seattle will spend an estimated 500 million to try and contain its combined sewer overflow problem by 2025.

Nearly 50 years ago, a public campaign of ballot initiatives called Forward Thrust tried to rein in Northwest problems, including polluted waters, unregulated sprawl and gridlock.

“The conditions were so abysmal,” wrote councilmember Jean Godden in a 2012 Crosscut article, “that visible bits of toilet tissue and other alarming detritus floated in Lake Washington."

Money was raised to begin to clean up the lake, but other waterways were left untouched and the combined sewer system remained. It wasn't until the 1980s that the city began to separate combined sewer and storm water pipes along shorelines.

When the EPA codified regulations for combined sewer systems in 1998, all of the city’s 12 waterways suddenly came under scrutiny. Seattle's new goal is to get overflows in the city’s 87 oufalls down to just one a year. Combined sewers built a hundred years ago have made the job extremely difficult.

"Every year the volume of overflow changes with the amount of rain, and it's not just the amount. It's the frequency, the duration and the intensity. It's all a factor," said SPU spokesperson Susan Stoltfus. “And because the pipes weren’t built for 154 million gallons of stormwater, when it rains in Seattle and it mixes with the sewage it's going to overflow because that’s the release mechanism for the system when its overwhelmed.”

Add a 20 percent jump in population from 1960 to the present, Growth Management Act mandates which require high density development in cities rather than urban sprawl, too few urban trees to absorb and contain runoff, and you've arrived at Seattle's new normal; a place where holding tanks and tipping buckets are required to — well — keep the shit from hitting the fan.

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