Wintertime street sand clogs sewers in Seattle

SEATTLE – Sand spread on streets during snowstorms in December is now sand in the gears of the largest sewage treatment plant in the area.

Sand flushed into the sewage system by rainfall this spring is clogging filters, filling catch-basins and wearing out pumps at the West Point plant in Discovery Park in Seattle, the latest in a series of problems caused by sanding rather than salting icy streets, the Seattle Times reported Monday.

On April 16, a pump was shut down, and one of four basins where grit is filtered from sewage before it is treated was subsequently closed for cleaning weeks earlier than usual at a cost of $1,200 in overtime.

Master maintenance mechanic Todd Smith said that in a decade of work at West Point, which has an average capacity of 133 million gallons of sewage a day, he has never seen so much grit.

The plant is owned and managed by King County but serves as the primary treatment facility for sewage and storm water originating in Seattle.

“We’re getting hammered,” said Wade Schrader, another maintenance mechanic.

It didn’t exactly come as a surprise.

Plant manager Pamela Elardo recalled her boss sending her a newspaper article about the 12,400 tons of sand spread by city transportation crews after a series of unusual snowstorms in the weeks before Christmas.

“I looked at it, and thought, ‘Oh, no,’ ” Elardo said.

The plant receives sewage mainly from Seattle but also from some of the suburbs north of the city.

In an e-mail to the Times, city transportation spokesman Richard Sheridan said more than 11,300 tons of the sand, nearly 91 percent of the total, had been swept off the streets since January. A private contractor was paid $42,000 to help with that effort after bicyclists complained of being injured in falls after skidding on sand heaps along some streets.

Annie Kolb-Nelson, a spokeswoman for King County’s wastewater division, said most of the grit at West Point – 2,800 tons this year compared with 300 tons in 2007 – came from the street sanding but could not give a precise figure. Other sources of grit include gravel and other inorganic substances.

Seattle Public Utilities has vacuumed sand from street drains but couldn’t say how much of that was from the snowstorms.

Under a long-standing policy, city officials declined to use salt to clear the roads because of concern about the impact on salmon habitat. The policy was reversed only after the storms had passed.

In an e-mail to the Times in February, Sheridan wrote that officials were confident the street sweeping was “preventing significant amounts of sand from entering catch basins and drainage pipes.” He did not respond to a telephone call for comment Monday from the Associated Press.