New storm-water guidelines differ technically

For most homeowners, storm water isn’t something they think about until their basements are filled with it.

But to engineers, developers and environmental agencies it’s a big deal. Big enough, in fact, that the federal government ratcheted down requirements for handling excess runoff in 1999, and those changes have finally made their way into regulations proposed for Spokane County.

“You can’t make it worse for anyone downstream,” said Matt Zarecor of Spokane County Development Services, summarizing the ethos of storm water regulations. That’s not a departure from rules in the county and its cities for two decades, he said. The differences in the new storm water manual will be in refined technical specifications slated for approval in Spokane, Spokane Valley and the county, he said.

With a few exceptions, new building projects on more than one acre can’t produce more runoff than the naked land. The manual addresses how that’s done, specifically how builders funnel petroleum-laden storm water from parking lots and other hard surfaces into the ground. The most noticeable change from the old rules likely will be smaller swales – the grassy pits designed to collect that water and filter out most of the pollutants before they reach the aquifer.

In Spokane Valley, a visible demonstration of that change might be the 20-yard by 40-yard fenced-off swale near Mission Avenue and Burns Road. Under the new regulation, similar to those adopted by Spokane Valley early this year, that pit could be about a third smaller.

Zarecor said design requirements that spread water over more of the grass would make the new swales as effective as the old ones and take up less space.

The city of Spokane is double-checking that to make sure the new swales meet federal pollution filtering requirements said Lars Hendron, principal engineer in the city’s Wastewater Management Department. Still, Spokane has worked closely with the other municipalities for the last year, and he said it will be beneficial to establish a consistent policy across jurisdictions.

The next step in moving the guidelines forward will be approval by the planning commissions and elected governments of Spokane, Spokane Valley and Spokane County in December or January.

For more information on the manual or to comment on the new standards, call Zarecor at 477-7255.

A draft of the document is available online at http://www.spokanevalley.org. Comments on the draft will be accepted through Wednesday.