By Lisa Stiffler
Stormwater -- the rainwater that streams off roofs, parking lots, roads, and yards, carrying with it toxic pollutants -- poses a costly, intractable problem for governments and businesses. In Washington, efforts to control stormwater have cost its cities hundreds of millions of dollars.
The problem with stormwater comes from its massive volume, which floods homes and blasts through streams, flushing salmon eggs, gravel, and everything else out to sea. And it comes from the pollutants that are picked up by the torrents of rain along the way, including copper, oil and grease, and pesticides.
Stormwater presents a daunting challenge considering the Northwest's rapid pace of development, and the fact that residential areas have three-times the rate of runoff compared to forests and fields (see page 12). Polluted stormwater kills salmon returning to urban streams to spawn before they can lay their eggs. It forces the closure of acres of shellfish beds made unsafe for human consumption. The rush of water causes erosion and fills basements with muddy water.
The good news is we already know some of the best, cheapest solutions for controlling runoff. The bad news is the solutions aren't being widely used.
A smart strategy for coping with stormwater is to prevent it from forming in the first place, and an elegant way to do that is to keep it from ever hitting the ground. Turns out that pine and fir trees are rain sponges, catching between 19 and 25 percent of the rainfall, according to a study of conifers in the Western Cascades (Table 1 of this study). Trees also trap rain by sucking it out of the ground and into their branches, and their roots help it penetrate the soil. Combining all three routes of rain capture, conifers in our region can catch about one-third of the rainfall, depending on how hard it's coming down.
A few governments are wisely putting a value on trees in the name of stormwater controls to encourage developers to protect them. Portland offers tree credits as a way for landowners to meet part of their stormwater mitigation obligation. Seattle is for the first time including credits for trees in its stormwater manual update (see section 4.4.6), which is expected to be approved by the end of the month.
But clearly even with incentives to keep trees, stormwater will be created in the Northwest by the barrel-full. So the next best strategy is to keep pollutants out of the runoff. Otherwise the stormwater has to be captured and treated, and many of the pollutants are difficult and costly to remove.
One of the bad actors that's been getting a lot of attention in recent years is seemingly innocuous copper. You can hold a penny in your hand with no harm done, but when the dissolved metal gets into streams it can wreak havoc on a salmon's sense of smell -- and they use their noses to find food, mates, their spawning streams, and to avoid predators. Scientists at the Northwest Fisheries Science Center in Seattle find that super low levels of copper -- levels that match what is found in nature -- deadens coho's response to an alarm pheromone that warns schoolmates that a predator is near.
So where does the copper come from? Research in the San Francisco Bay area found that the top two sources of human-caused copper pollution come from pesticides (42 percent) and brake pads on cars and trucks (36 percent). Some of the pesticides' copper gets trapped in the soil and plants, putting more of a focus on the brake pads copper that travels from roadways and the air to waterways.
Now California's Brake Pad Partnership, a nonprofit coalition of environmentalists, engineers, and auto reps, is working to get legislation passed that will get copper-containing brake pads off their roads. Their Q & A sheet gives a great explanation of how the copper is scraped off the pads when a car brakes, why it's used, and what the substitutes are (they include steel and iron). Here's the most important piece:
"Copper-free brake pads of all types are available and in common use.
Because zero-copper products are currently used in many vehicles that
meet federal vehicle safety standards, it appears that the presence of
copper is not necessary for brake pads to function safely, providing
that the friction material, in conjunction with the brake system, is
suitably engineered for those vehicles."
Stormwater flooding photo courtesy of Flickr user technokitten under the license.
This piece originally appeared in Sightline.org