Remember the good old days when you could self-righteously point to spewing smoke stacks and foul outfalls as the big polluters? These days, when it comes to Puget Sound’s water pollution, we’ve met the enemy and he is us.
For the majority of contaminants sullying the Sound, they’re getting there via stormwater. Stormwater is the rain that streams from roads, parking lots, roofs, highways, and some landscapes washing toxic chemicals along with it.
Stormwater flowing from the developed landscape is the No. 1 source for lead and petroleum products getting into the Sound. Runoff contributes 35 times more mercury to Puget Sound than industrial polluters, according to estimates from a Department of Ecology study. A follow-up report estimates that stormwater is dumping 134 metric tons of copper into the Sound each year—that’s the weight of more than 53 million pennies (copper can prove deadly to salmon by deadening their sense of smell, which is used for finding food and mates and avoiding predators).
How can a little rain wreak so much havoc?!
It turns out that the wet Northwest produces tidal waves of stormwater each year. There aren’t great numbers available for the total amount (Ecology’s trying to better answer this question in upcoming studies), but you can get a sense of the volume just by looking at what comes from a single house.
A good-sized rainstorm falling on a house with a 1,200-square-foot roof could send about 10 bathtubs full of water out of the home’s downspouts. And that’s just one storm, at one house. Over the course of an average year in Seattle, approximately 400 bathtubs worth of water are gushing off that single roof.
And the stormwater situation will only get more challenging as the Puget Sound likely continues its rapid pace of sprawling development. That’s because when you take farmland, grassland, or forests and turn them into houses and roads, you can expect to double or even triple the amount of runoff racing off the landscape (again see Ecology’s phase 2 study). That argues for more compact, high-density development that leaves more of the natural landscape untouched so that it can sponge up the rain where it falls.
So how does a drop of rain make its way to the Sound? In an older city such as Seattle or Tacoma or Everett, the rain runs from roads and roofs into gutters and ditches, which empty into creeks and streams, and they lead directly to the sea. That’s a largely straight shot to the Sound, bypassing any kind of treatment to remove toxic chemicals and sediment, or to slow the flow to reduce erosion.
In some cases, the stormwater is piped into the sewer system, in which case it gets treated along with the waste from your toilets and sinks (unless there’s so much rain that the system overflows and untreated sewage and runoff get dumped into the Sound through a Combined Sewer Overflow, or CSO).
In newer developments or redevelopment, the stormwater might be channeled into ponds that hold the water and allow it to soak more slowly into the ground, or it goes into underground “vaults”—perhaps under a big parking lot—that also catch and hold some of the water allowing dirt and other particles of pollution to settle out. The trouble with these systems is that while they can provide some level of treatment, it only works if the dirty basins are regularly cleaned out and the sediment disposed of, which is a costly undertaking and may occur infrequently.
What’s better is something called “Low-Impact Development” where buildings and landscapes are designed to trap most of the rainfall on site rather than allowing it to runoff. LID projects—which can be applied to new construction or retrofitting developed areas—use strategies including porous driveways and sidewalks, rain gardens, and rain barrels. Stay tuned for more on LID in a later post.
Rain gutter photo courtesy of Flickr user jc.westbrookunder a Creative Commons license.
Uncle Vinny
Where in the world is all that copper coming from!? Is it from the lining of the gutters, downspouts and other water channels? This is incredible to me…
Lisa Stiffler
According to research done in San Francisco, it’s mostly coming from car and truck brake pads. In fact, they’ve formed a coalition there called the Brake Pad Partnership that’s studied the source of copper in the Bay and brake pad alternatives. They’ve proposed a phased-in ban of copper-free brake pads (they’re already available), but held off on pushing the legislation until next year.
Uncle Vinny
Thanks! I hadn’t considered that source, or had only generically thought of “cars” as a possibility… Yet another reason to find other ways to move around.
Uncle Vinny
I’ve been mulling this over all day, and it just seemed crazy to me that we could be dumping so much copper in the Sound. “134 tons of copper per year!?”, I kept thinking. So, in true Sightline fashion, but in my own amateur way, I started Googling. (Well, I’m a former MSFT-ie, so I’m “Binging”. Ugh.)How many cars are there in the Puget Sound area?~250,000,000 cars in the US. Greater Metro area of Seattle is 3.34 million people, to the US’ 308 million, means we’re about 1.1% of the population (Puget Sound as a whole probably has more than that, but I’m ballparking.) 1.1% of 250M cars is ~2.7M cars.134 tons of copper/year works out to 1.6 ounces per car per year, or .4 ounces of copper/brake pad/year; this is about 1.2 cubic centimeters in volume, or the weight of 10 plastic pen caps. These numbers don’t seem crazy to me…(I’ve left out trucks, which also wear down their brake pads, so each car probably only needs to contribute half of that .4 ounces per brake pad. My guess is that railroad cars also grind a heck of a lot of copper dust when they apply the brakes, but that may be only a tiny contributor.)I would love to find some info on the web about typical brake pad dimensions, to guess how much material is wearing off between when it’s new and when it needs to be replaced; this would be another reality check on whether we’re in the right ballpark. But based on my little calculations, I’d say it’s entirely plausible that a big part of that copper really is coming from brake pad dust. Incredible.
Lisa Stiffler
Well done! (And I’m glad that penciled out!) That’s the crazy thing about stormwater. I think it’s hard for people to get their head around the idea that the small actions that they take as an individual are having this detrimental effect when taken en masse.
WorkingDad
Lisa, It is great to see you are still on the beat. I missed your great writing and clear style. We’ll need to review what we are doing around our house. Great story.