Green infrastructure protects salmon waters

Learn to filter stormwater so that we don’t run off salmon. By Kristen Carpenter For The Cordova Times

Andy and Laura Hanson stand in front of the engineered sediment basin on their Center Drive lot in July. Photo courtesy of Copper River Watershed Project
Andy and Laura Hanson stand in front of the engineered sediment basin on their Center Drive lot in July. Photo courtesy of Copper River Watershed Project

This past summer Copper River Watershed Project worked with private property owners Ardy and Laura Hanson to install the latest piece of Cordova’s “green infrastructure” to prevent stormwater pollutants from draining into Odiak Pond, home to pink and coho salmon, waterfowl and beavers.

CRWP used Alaska Department of Environmental Conservation grant funding to install a perforated pipe drain that collects water below the earth’s surface and directs it to an existing creek bed, keeping rain water from washing across the Hanson’s lot where it could pick up pollutants.

What is “green” infrastructure, and why is it important?

Stormwater runoff, or all the water flowing across parking lots and streets, is a leading cause of water pollution in developed areas. Leaked vehicle fluids, heavy metals, sediments and bacteria are all swept into our creeks, lakes and nearshore ocean waters during heavy rain. Traditional street design uses “gray” infrastructure – pipe drainage and water treatment systems – to move water away from our homes and stores, but it doesn’t filter those pollutants out.

“Green” infrastructure uses a combination of vegetation, soil and drainage structures (e.g. sediment basin or slope drains) to filter stormwater at its source before the runoff is discharged into nearby waterbodies.

Water sampling conducted by CRWP in 2015-2016 at Odiak Pond and at the outfall to Orca Inlet showed levels of heavy metals (copper, lead and zinc) above State water quality standards, demonstrating the need for filtering stormwater before it hits our local waterbodies. Copper is harmful to fish because even very low levels inhibit their ability to smell, which they use to avoid predators and navigate.

The Hansons’ lot is marked on a 1980 sub-division plat map that shows a stream flowing down the hillside above the Copper River Highway and across several properties that now line Center Drive.

Kate Morse in front of the bioswale planted with native wetlands plants, behind Cordova Community Medical Center in June 2015. Photo courtesy of Copper River Watershed Project
Kate Morse in front of the bioswale planted with native wetlands plants, behind Cordova Community Medical Center in June 2015. Photo courtesy of Copper River Watershed Project

The stream was filled in to create the lot they now own but the hillside drainage still flowed, resulting in standing water on the property and a lot that was hard to build on.

The new filtration system constructed on the property includes a trench drain and a sediment basin to collect water below the lot’s surface and filter remaining surface runoff before discharging water to a stream channel on the neighboring property.

To make way for water exiting the trench drain, Ardy Hanson and Eagle Contracting helped bring the stream channel on the adjacent property to daylight by excavating stumps and buried concrete chunks.

A Student Conservation Association crew working in Cordova this summer planted native vegetation along the streambanks to prevent erosion and provide additional bio-filtration.

Another significant element of this project is the “matching” contributions made by local contractors. State and federal grant sources often require an applicant to bring additional funding or a “match” to the project.

Wilson Construction and Eagle Contracting helped us meet this match requirement by spending their own time moving piles of equipment away from the channels adjacent to their properties that drain to the Center Drive/Odiak Pond neighborhood.

With the equipment cleared, they created vegetated buffer zones that will intercept and filter rain or melting snow flowing across their yards to the drainage channels that both lead to Odiak Pond.

Other points of filtration that we’ve added to Cordova’s green infrastructure include a bioswale behind the Cordova Community Medical Center where a channel meander and plants slow down and filter street and parking lot runoff, and improvements to two snow storage sites (Hollis Henrichs Park and 2nd and Adams streets, behind the old library) for filtering sediment and attached pollutants from melting snow.

We can all help prevent storm water pollution from entering our salmon creeks, ponds, and lakes by checking our vehicles for leaky fluids (look for dark spots in your parking area), and planting or maintaining vegetation around our property to help filter surface run-off.

For more information on what we’re doing to reduce stormwater run-off, visit copperriver.org to sign up for our newsletter or follow us on Facebook.