January 26, 2009 in City

Stormwater diversion will ease river pollution

Mike Prager
 
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Current system

 Stormwater on the South Side is piped into sanitary sewers. The system is designed so that, during heavy runoffs, excess water spills into the river as a mix of diluted sewage and stormwater to prevent flooding at the wastewater treatment plant.

 The proposal calls for diverting about three blocks of stormwater into a subterranean trench on the west side of Cannon Hill Park.

Spokane city stormwater engineers think they’ve come up with a way to reduce pollution going into the Spokane River, and they have enlisted the support of residents in the Manito/Cannon Hill Neighborhood to get the idea moving.

The experimental project involves building small stormwater collection basins along Lincoln Street near Cannon Hill Park this summer and diverting some of that water from the city’s sewer system.

It comes as the city is about to tear up and rebuild Lincoln Street from 17th to 29th avenues during the next phase of a 10-year, $117 million package of street repairs approved by voters in 2004.

Dale Arnold, director of the city’s wastewater department, said wastewater engineers hope to piggyback on the street reconstruction to try out a system that’s been used in other cities but not in Spokane.

A resolution endorsing the proposal goes before the City Council during its 6 p.m. meeting today at Council Chambers at City Hall.

Neighborhood council Chairman Dennis Anderson said the idea has won support because it provides an environmental solution to a long-standing problem of keeping the river clean from pollution.

“It’s a win-win situation from an ecological point of view,” he said.

City officials and neighborhood residents have been working together over the past year to fashion the project, estimated to cost about $1 million out of the city’s wastewater utility fund.

Engineers are asking the City Council for permission to use a small portion of the street along the curb to install small new stormwater collection areas in the form of “curb extensions” that would use soil and naturally existing bacteria to hold and treat the first half-inch of stormwater that flows into them. The collection areas would double as small planting strips, and the soil would break down residues that come from motor vehicles and fertilizers.

That would reduce the volume of water going to the city’s wastewater plant and keep pollution out of the Spokane River.

The idea enhances city efforts under the federal Clean Water Act to reduce pollution in the river.

Stormwater on the South Side is piped into sanitary sewers. The system is designed so that during heavy runoffs excess water spills into the river as a mix of diluted sewage and stormwater to prevent flooding at the wastewater treatment plant near Riverside State Park.

The proposal also calls for diverting about three blocks of stormwater into a subterranean trench on the west side of Cannon Hill Park.

The idea is similar to stormwater collection systems used in Western Washington and in Portland, but it would be the first time the concept has been used in Spokane, Arnold said. “It’s going to set the stage for other projects,” he said.

Lincoln Street was chosen because traffic flow allows for one lane in each direction, rather than two. That means there is enough space adjacent to the existing curbs to build small collection areas without impeding traffic. Concrete curbs with inlets would be built in strips about four feet wide along each block to collect the water.

The collection areas would also have the effect of slowing traffic through the area, including a school zone for Wilson Elementary School.

Arnold said city workers have contacted residents along Lincoln as well as the neighborhood council to enlist their support, and have so far received a positive response. Anderson said the idea received approval of about 80 percent of residents, and that those living along Lincoln who object to the curb extensions would not have them built in front of their homes.

The city is in the middle of a $500 million project to upgrade the city’s sewage collection and treatment system to meet evolving standards for water quality in the river. Arnold said he expects that the state and federal governments will continue to press Spokane to make additional improvements. The small street collection systems are part of that larger effort, he said.

Stop sign removal

Spokane city workers last week posted a notification that stop signs at 26th Avenue and Arthur Street are going to be removed after a citizen complained that few drivers were actually stopping at the intersection, city officials said.

Traffic engineers took a look and found that the stop signs did not meet citywide standards for four-way stops, which are typically used on arterials, not residential streets, and that traffic volumes are low and visibility at the intersection is good, according to Ann Deasy, spokeswoman for city public works.

In addition, the intersection has had no reported accidents in the past 10 years, she said.

The notification period lasts for 30 days. Comments can be directed to traffic engineer Bob Turner, 232-8812, or bturner@spokanecity.org, until Feb. 23, Deasy said.

Mike Prager can be reached at (509) 459-5454 or by e-mail at mikep@spokesman.com.


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