When it rains heavily in Magnolia, it pours - sewage into Elliott Bay.
The event is called a combined sewer overflow (CSO) and takes place when stormwater overwhelms the system so that untreated sewage mixes with the stormwater and is dumped into the bay.
It happens an average of 10 times a year at the CSO several hundred feet out in the water from a popular beach at the end of 32nd Avenue West, according to Annie Kolb-Nelson from King County's Wastewater Treatment Division.
That poses an obvious health risk to people and animals in the waters off the heavily used beach, but the county has plans to reduce the local CSO to once a year, she says. "King County has plans to control all of our CSOs by 2020."
It's a change mandated by state law, Kolb-Nelson explained, and the south Magnolia CSO fix is one of four priority projects the county plans to tackle in the near future. One of the others is at North Beach near Carkeek Park, and two of them are in West Seattle, she added.
"We're still in the very preliminary stages of design right now," Kolb-Nelson went on to say.
But the county will have a list of alternatives ready by next fall, she added. "And that's when we're going to go out to the public and get their ideas."
Still, there are only three approaches that can be taken, according to an informational flier the county has released about the projects.
One way, Kolb-Nelson said, would be to store the combined sewage and stormwater until it can be treated at the West Point sewer plant by using either a tank that would probably be above ground or a large pipe that wouldn't.
The second is to reduce the flow of stormwater into the sewage system. "So one of the options ... is working with community members to disconnect downspouts that [drain] into the sewer system," she said.
That could be a problem because the stormwater still has to go somewhere, and it could pose a danger to steep slopes, Kolb-Nelson conceded. "That's one of the things engineers are looking at. It may not be feasible."
The third alternative would be to treat the waste and stormwater at the site before it is discharged into the bay. "Actually, if we pursue that option, we're looking at something with a small footprint," she said of a facility that would most likely be located above ground.
A ballpark estimate for the neighborhood CSO project comes in at under $10 million, and the money would come from ratepayers throughout King County, Kolb-Nelson said.
There is a two-tiered system in place. The rate for new homes is $42 a month in addition to a $27.95-a-month charge existing customers pay, she said.
"The idea is the rates should stay stable for existing customers."
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