Commentary By Kristin Carpenter
For The Cordova Times
Just because this is the time of year when we expect to see our precipitation in the frozen form, rather than rain, doesn’t mean efforts to mitigate stormwater pollution can be set aside until spring. In its pure state, snow is a beautiful blanket of white that brightens up our winters. When it’s plowed from the streets and stored until spring, though, melting snow releases a big pulse of street pollutants that drain to our creeks and ocean. Stormwater is water from rain or melting snow that “runs off” across hardened surfaces instead of seeping into the ground.
A rural, coastal village like Cordova, with its population of 2,200, might not seem to be a likely source of excessive stormwater run-off pollutants. But water quality sampling conducted by the Copper River Watershed Project in 2015 – 2016 found that levels of copper exceeded State of Alaska water quality standards in 9 of 12 samples, at rates ranging from 5 to 30 times the State limits for salt water, and from 2 to 6 times the limit for fresh water. The samples in which copper did not exceed the allowable limit were collected during dry periods.
Levels of copper as low as 2 parts per billion impair salmon’s sense of smell, inhibiting their navigation and predator avoidance abilities (Brown, 2007). Lead and zinc were also found to exceed State standards in several of the samples. For a community that depends on commercial fishing supported by clean streams and ocean waters, this is a conflict.
The Copper River Watershed Project has been working with the city of Cordova to analyze snow handling and storage practices, and to look for “best management practice” (BMP) improvements that could be implemented to allow for more filtration of melting snow. Upgrades to the City’s largest snow storage site behind the old library were just completed two weeks ago so that the site will be ready for use this winter. Improvements include excavation of a sediment basin, and re-grading the adjacent parking area to direct drainage of melting snow to the basin. Rip rap channels sloping to the basin and the basin itself will slow down melting snow, allowing sediment to settle out before the meltwater drains to the storm drain system, and ultimately to the near shore marine environment of Orca Inlet. Sediment, like road sand, can be a pollutant itself in rivers and creeks, and it also picks up the hydrocarbons that drip from our leaky vehicles and heavy metals which come from brake pads and tires.
The challenge of stormwater, or “non-point source” run-off, is that it’s diffuse, as indicated by its technical name. And even though it drains through the “storm sewer” system, polluted run-off typically isn’t treated by municipalities before it drains to our creeks and ocean. But by intercepting that surface flow at key points and directing it to constructed BMPs, stormwater can be filtered before it’s discharged to community waters. These treatment structures can be engineered bio-swales, small constructed wetlands, or detention ponds that collect run-off where wetland soils and plant roots break down pollutants. Have you noticed the vegetated channel behind our medical center that drains to Odiak Pond? Then you’ve seen a bio-swale!
Stormwater is considered a leading threat to clean water, but solutions for treating it are available on several levels. Individually, we can take care of our leaky vehicles by repairing those leaks, or placing an absorbent pad under the vehicle or piece of equipment when it’s parked. Another action we can take to reduce stormwater pollution is consider installing copper-free brake pads the next time you replace your brakes or buy a new vehicle. California and Washington have already enacted legislation to phase down the amount of copper and heavy metals in brake pads to .5 percent by 2025. In a memorandum of understanding with the EPA, auto manufacturers have agreed to use pads that contain no more than 5 percent by weight of copper by 2021.
Leaving vegetated buffers along stream banks and lake shoreline allows for natural filtration of polluted run-off. The CRWP will continue to work with the city of Cordova to identify key locations where surface run-off can be intercepted for filtration before it makes its way to fish-bearing water bodies within our community: Eyak Lake, Odiak Pond, Eccles Creek, Heney Creek, and Orca Inlet.
Funding for this project came from the Exxon Valdez Oil Spill Trustee Council and th National Fish and Wildlife Foundation.
Kristin Carpenter is the executive director for the Copper River Watershed Project.
