Our Little Creek with a Mind of Its Own

 

by Judith Starbuck, Grand Avenue, interview with Peggy Gaynor, Gaynor, Inc.

Our Madrona Woods restoration group hopes you’re enjoying the Madrona Creek as much as we are. I especially love the sound of it from the bridges. Landscape architect Peggy Gaynor is the mastermind behind the Madrona Woods restoration, and in particular the daylighting of Madrona Creek. Our January work party included repair to that creek, with Peggy’s guidance on patching and shoring up places where the water was going where it wasn’t intended to. Here are some of Peggy’s thoughts on creek maintenance.

JS: Did you foresee how many times our group would need to bring the creek back into its constructed banks when it had either gone off to the side or into a hole?

PG: No. We have discovered a lot of concrete debris that was dumped in the ravine where the creek flows. The dumping was done back in the days when environmental concerns were not on the radar. This has created voids under the surface, and water has a way of finding the path of least resistance—these voids in this case. A number of times the water has seemed to disappear into a hole, and we’ve had to patch the stream bed to get it back on course at the surface. We don’t want the stream to continue underground and possibly undermine Lake Washington Boulevard. We use a natural clay called Bentonite, which expands when mixed with water and seals off these areas like the caulk in a bathtub. First filling the void with mud and gravel, then a mix of Bentonite and sand topped with a protective layer of rocks and gravel plugs the “leaks,” but some have required more than one fix.

JS: How does our creek compare with other daylighted creeks you’ve worked on?

PG: This creek daylighting was more challenging due to elevation change (over 750 feet elevation gain from Lake to headwaters) and the unknown soil/landfill issues along the creek corridor mentioned above. So far this is the only daylighted stream that goes from its headwaters in springs in the hillside between 37^th and 38^th streets into the lake. Though the distance is short, just over a quarter of a mile, it’s providing fresh water and nutrients for salmon migrating along the shore of Lake Washington.

JS: How do you see creek maintenance in the future?

PG: Future maintenance should be more of a partnership between Seattle Parks and Friends of Madrona Woods, and it will likely involve some additional expertise and consultation for long-term solutions, especially for the “leaks” and sinkhole issues. Experts could include geotechs and even stone masons. It will still be up to Friends’ volunteers to keep watch on the creek and notice when it seems to be going astray and needs attention.

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• Mission Statement

  The Friends of Madrona Woods strive to restore the Woods to a healthy, natural state by removing non-native invasive plants and revegetating with diverse native plants and to make the Woods safe and accessible through an environmentally friendly trail system.