Filtering Street Runoff Through The Natural Filters Found To Help Salmon.
By Andy Walgamott
SHORELINE, Wash.—Even if it’s an almost miniscule bandage on a region that needs so many more of them, I’m feeling pretty good about turning a gravel strip into a rain garden.
Yeah, there’s a lot less parking at our house just north of Seattle, and we probably hurt our property value, but new research suggests that filtering street runoff can really help out young salmon and the bugs they feed on. And while I was thinking more about adult coho than wee ones when we came up with the idea, it’s kind of hard to get any of those to return if they can’t survive in urban streams in the first place.
IT ALL BEGAN one rainy Saturday morning several years ago as I absent-mindedly washed the dishes. Staring out the kitchen window, my eyes settled on water running down a slight divot in the street.
A lot was actually flowing past.
It wasn’t the first time I’d noticed the little “creek” that springs up every time it comes down hard. One winter day, when warm temps were rapidly melting snow, our oldest son, River, and I put our boots on and tried to dam the water as it gushed towards a grate that funnels into Thornton Creek.
But it was that exact moment I decided to do something about it. In giving our house a lodge look with a few of my bucks’ racks over the door, Amy, the boys and I have worked to certify our yard as wildlife habitat. (In addition to tweety birds and the neighborhood squirrels and raccoons, a blue heron has stopped by twice – albeit to try to poach our goldfish.) And along with raising chickens for eggs and putting in gardens to grow wholesome berries, tomatoes, potatoes and peas for ourselves, we wanted to do something for salmon too.
When I’ve looked closely at the street runoff, it’s grayish. Maybe that’s because of the asphalt underneath, but the water carries drippings from our cars and those parked up the street, plus pesticides, herbicides – just all sorts of bad mojo that can’t be good for Thornton’s fish.
And it’s not, scientists have shown in recent years. Intuitively, it just makes sense that salmon and trout wouldn’t do well in that brew, but it wasn’t until researchers began to monitor West Seattle’s Longfellow Creek that the magnitude of the problem became jaw-droppingly apparent.
According to a 2013 report, adult coho hens fresh out of Elliott Bay were dying in Longfellow within hours of rainstorms. Tribal and federal researchers were able to establish that untreated storm runoff collected from highways was the cause, but it’s still unclear what compound(s) is responsible. The upshot is, with the return of salmon coinciding with the onset of rainy season in the Northwest, if fish can’t live long enough to spawn, theoretically that leads to fewer and fewer in the future.
And then, this past winter, scientists at the U.S. Fish & Wildlife Service, National Marine Fisheries Service and Washington State University showed that runoff taken from a highway cutting through the Emerald City killed every single juvenile salmon subjected to the swill in less than half a day. So, not only are returning adult silvers getting hit by poison during fall, but the offspring of those that spawn have to somehow withstand it during the year or so before they escape to sea.
It’s kind of staggering. Go to Google or Bing Maps and see all the gray in Pugetropolis and Portlandia that is pavement and parking lots. Add an average of 35 to 45 inches of rain on top of it, and that water’s gotta go somewhere – and it doesn’t always get piped to treatment plants.
It’s a problem on par with The Blob that hung out in the Northeast Pacific last year and the persistent ridge of high pressure that kept us warmer this past winter: Just how in the heck do you wrap your mind around something this big, let alone do something about it?
It’s not like we’re going to rip up the streets – or are we?
Essentially, that’s what we decided to have done outside our house.
AMY, RIVER, KIRAN and I live near where the mainstem of Thornton Creek sneaks in and out of the old peat digs known as Ronald Bog and Twin Ponds. (Not to brag, but I’ve got the bass – as in the only one – of the bog dialed in, and will catch him again this spring.) The creek is then collected to pass underneath busy Interstate 5 and NE 145th, reemerging at Jackson Park Golf Course inside Seattle city limits, thence through the densely populated Pinehurst, Lake City and Meadowbrook neighborhoods, before gurgling into Lake Washington at Matthews Beach.
Last November, we walked a trail along the golf course. As the boys showed off their balancing skills (as well as their lack thereof) on the creek’s slick rocks, I looked for coho, either alive or decaying back in the weeds.
Cars and trucks roared past on I-5 just dozens of yards away, and while under one footbridge there was a pile of spawned-out beer cans, there was no sign of salmon, nor smell of dead ones.
We walked on.
Talking with a longtime Shoreline resident awhile back, she told me about two adult salmon that were found above the interstate several years ago; her expression told me she didn’t buy the story. However, a city report says a state fisheries biologist observed a 2-plus-foot-long steelhead finning in a pool between the ponds and bog. The fish had minor abrasions, but appeared all right. Coho fry were also seen in the golf course reach.
However, that city document is from way back in May 2004; it’s been far bleaker in recent years. Seattle and King County biologists tell me 2014 was a “bust” for salmon. Students at Nathan Hale High School, located on the lower end of Thornton near where two branches of the creek come together, saw no Chinook, coho or sockeye during daily inspections last fall.
If there’s good news, it’s that the biologists believe lots of cutthroat – something like 600 annually – use Thornton for spawning in winter and spring.
NEITHER COHO NOR cutts will ever swim into our rain garden, but being in the headwaters of the creek and with more than a passing interest in salmon and wild things, we had a chance to do something. We broached the idea of turning the gravel pad in the public right-of-way into a rain garden with Shoreline’s Public Works Department. They liked it, drew some designs up, and, after some more discussion, hired a contractor.
Last summer, crews brought out their backhoes and dumptruck, cleared off the gravel and asphalt, and made a V-shaped trench 25 feet long, 7 feet wide and up to 4 feet deep. At the bottom they put in a French drain connected to a new elevated grate. The trench was filled with sand and pebbles topped with a funky mix of soil that was sculpted with some berms to try and slow the runoff so it percolates downwards. Crews came back in winter and planted ferns and sedges.
To be honest, the berms haven’t stood up so well to gullywashers, and some water still flows down the street, meaning it bypasses the rain garden entirely and gets into Thornton Creek untreated. But overall I’ve been impressed at how much water can otherwise be trapped in the garden.
And as it turns out, filtering like this is an “affordable and remarkably effective” treatment for street runoff, according to federal and university researchers. They found that pouring it through a “simple” 60-15-15-10 mix of sand, compost, shredded bark and water-treatment residuals “reduced toxic metals by 30 to 99 percent, reduced polyaromatic hydrocarbons that are byproducts of fossil fuels to levels at or below detection and reduced organic matter by more than 40 percent,” according to NMFS.
Not only did that provide juvenile salmon with “complete protection against the lethal toxicity of stormwater runoff,” but the bugs they prey on were shielded from damage to their reproductive capabilities too.
“This is a simple approach that can make a big difference in the quality of water flowing into our rivers and streams,” said Jenifer McIntyre, the WSU postdoctoral researcher who has been running the street water through barrels in her lab. “In this case, the salmon and their prey are telling us how clean is clean enough.”
AROUND 200,000 LIVE in Thornton Creek’s 12-square-mile watershed, Seattle’s largest creek system, and driving around it with the boys in early March reinforced to me just how tiny of a fix our rain garden really is. But it’s a start.
Actually, it’s more like part of a building movement that aims to trap or slow runoff, be it from streets, parking lots, driveways, roofs or other impervious surfaces. A website, 12000raingardens.org, has an ambitious goal to register that many in Puget Sound by next year (they’re currently up to 1,000), and the rural town of Eatonville east of Tacoma has been dubbed the “rain garden capitol.” Many Puget Sound cities offer rebates for installing them on private property, and federal funding is also available. Ours cost us nothing except lost parking space.
Trapping polluted runoff is but one part of helping urban salmon recover. Removing passage-blocking culverts, shading lakes and streams, removing invasive species, and improving habitat are more visible things that can help, and generate good headlines, like last fall’s first return of coho to Crystal Springs Creek in Portland.
In Thornton’s lower end near Nathan Hale, the City of Seattle’s Meadowbrook project is Goliath to our David of a rain garden. While created primarily to address flooding – a settlement pond also captures sediment so it can be removed – it includes a new, more fish-friendly streambed complete with large embedded logs and stumps, and a 2-acre floodplain.
When the boys and I surveyed it, signs in the area warned us not to enter the creek because of pollution – a travesty, I thought, because it seems like half of my days growing up outside Sultan, Wash., were spent wading nearby waters – but waterfowl fed in the pond while crows frolicked in the new channel. The creek was a lot bigger there than up at our house, where a rain garden attempts to slow and treat street runoff in hopes that one day salmon will again run up Seattle and Shoreline’s backyard stream, and the eggs they lay will hatch and grow and return again.