Collateral Improvements: Spokane Rainwater Project means upgrades on the Downriver Disc Golf Course

On a hot Tuesday at 9:30 a.m., golfers played 18 holes on the Downriver Disc Golf Course, trying to thread their discs between bushes or looping around towering ponderosas.

It’s not surprising that people were willing to sweat buckets and get up early to find the links here. The northwest Spokane course is picturesque, nestled in a bend in the blue-green Spokane River, and full of blooming flowers and birdsong.

The course is nice, but also a bit disheveled. That should change soon when the square is renovated and redesigned this summer as part of a major rainwater management project.

The disc golf course upgrades are an added benefit. The course is being redesigned so that the city can install infiltration ponds that filter pollutants from the rainwater from the Cochran Basin. The disc golf makeover is tangential.

“We care about a cause that we have, but at the same time we deliver a better community life,” said Marlene Feist, Spokane public works director.

Rainwater management may not be a priority for many Spokanites, but the city has been working on improving its system for decades. The Cochran Basin makes up a large part of the city’s rainwater management.

The basin covers 5,328 acres of northern Spokane and represents approximately 60% of the city’s segregated rainwater system. It extends east to west from Alberta Street to Market Street and north to south from Francis Avenue to Montgomery Avenue.

All of the rainwater in the Cochran Basin that does not seep into the ground has to go somewhere. Every year the city drains between 350 and 500 million gallons of rainwater from the Cochran Basin into the Spokane River. When it rains, a large pipe near the TJ Meenach Drive Bridge gushes water.

That may sound good. After all, rainwater is just rain and snowmelt – at least initially. But as it flows through the streets, it picks up a range of contaminants: motor oil, scrap rubber, metal filings, and landscaping chemicals, to name a few.

These pollutants pollute the Spokane River and can have a negative impact on wildlife. There’s no immediate need for Spokane to clean up the Cochran Basin stormwater system – at least there are no urgent government contracts – but Spokane’s estimated $ 20 to 30 million investment in pipes, storage tanks, and infiltration basins for the Cochran Basin project will help the city comply with possible future regulatory changes.

The disc golf course’s infiltration ponds are key to keeping toxins out of the river.

There will be six ponds that will cost $ 2.5 million that will hold and filter rainwater. Plants at the pond edges suck up contaminated water. Sand, compost and fine materials filter out more pollutants when water seeps into the soil.

“The goal here is to treat it like nature would,” Feist said.

Kyle Twohig, Spokane’s engineering services director, said the infiltration ponds may sound uncomfortable, but they do an excellent job of cleaning rainwater before it gets back into the river.

“When it’s 3 meters underground, it’s really very clean,” said Twohig.

The ponds will be able to handle most of the rainfall and snowmelt in the Cochran Basin on their own. Twohig said they will be built to hold 240,000 cubic feet of rainwater. That’s how much water it takes to fill 2.7 Olympic pools.

The system won’t be able to handle the biggest storms and snowmelt, but Twohig said the ponds are designed for anything but six-month rain events. This means that roughly twice a year rainwater either flows untreated into the river or flows into additional storage capacities that will be built along the TJ Meenach Drive over the next year.

Twohig said the pond water poses no threat to people who play disc golf. Dumping large amounts of rainwater into the Spokane River could cause ecological damage, but rainwater won’t hurt anyone’s hand when they reach for a stray glass.

The asymmetrical ponds will cover a large part of the disc golf course. They are integrated into the new course layout – golfers have to throw themselves over the water on several holes.

The infiltration pond project has not yet been tendered, but Feist said construction will start this summer and finish in the fall.

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