Month: June 2011

By Allison Barrett

On the side of Mark Davison’s house stands a huge tank. Over 6 feet tall, the cistern is designed to capture runoff from his roof. It only drains a small, 400-square-foot portion of the roof, but during a recent spring rainfall that section of the roof produced enough runoff to fill the 650-gallon tank to the brim.

Without the tank, those hundreds of gallons would have poured directly into Ballard’s sewer lines, an outdated system that frequently overfills and dumps a mess of dirty rainwater and raw sewage into Salmon Bay, making Ballard one of the city’s top perpetrators of polluting Seattle waterways during a rainstorm.

But the city is offering Ballard residents ways to slow down the rain, diverting it into cisterns and rain gardens, as part of a program that is designed to decrease the frequency of polluted overflow.

“We took away a lot of natural infrastructure for dealing with rain,” said Ann Butler, who works with People for Puget Sound and helped lead a bicycle tour on Saturday, June 4, to look at Ballard homes with successful catchment systems.

An intern with People of Puget Sound examines the landscaped retaining wall on a Ballard rain garden. They can vary in design depending on the site.

Impervious rooftops and hard cement surfaces funnel rain into our waterways instead of letting it filter into the ground, she said. On the way, runoff picks up all kinds of pollutants like heavy metals, oil and fertilizer chemicals.

“Percolating it into the ground slows the process,” Butler said.

And the city has to slow the process and cut back on the occurrence of sewer overflows in order to comply with the Clean Water Act. According to Seattle Public Utilities, there are two major sewer outfalls in Ballard that comprised about one quarter of the city’s entire overflow problem in 2010. More than 43 million gallons of sewage and stormwater were discharged into Salmon Bay. Sometimes the overflows happened after as little as one tenth of an inch of rainfall.