OPINION: THE SR520 EXPANSION BETWEEN THE SAMMAMISH RIVER BRIDGE AND REDMOND WAY - From 4 lanes in 1992 to 8 lanes in 2008. But at what cost?

How many people remember what traffic was like on 520 in Redmond in 1992 when the freeway expansion and improvements were first approved? Back then, the eastbound lanes of 520 ended at the stoplight on Redmond Way and cars waited in line to cross onto Avondale Road or turn left or right onto Redmond Way. A trip from Overlake in Bellevue to UPS on Union Hill Road in the afternoon could take an hour or more. The addition of the flyover so that cars didn’t have to stop at the light on Redmond Way was such an improvement (although everyone was dismayed when it only had one lane in each direction.) In the past year, an additional flyover was built to allow traffic from westbound Redmond Way to flow directly onto 520 without stopping at the traffic lights on Redmond Way. This summer the Department of Transportation plans to start adding four additional lanes to 520 so that there will be four lanes in each direction. The new lanes are to be built on the north side of the freeway in the area now occupied by the Bear Creek floodway. click picture to enlarge


In 1992, the Redmond Town Center site was an empty field that had been a golf course and before that, a farm. The land was part of the Bear Creek 100-year flood plain so when a major storm occurred, storm water from Bear Creek could flood north towards the railroad tracks where the main parking garage, REI and Macy’s are now located. The whole area could flood to a depth of 2 to 3 feet for a day or two and then the floodwater would recede. When Redmond Town Center was constructed, most of the site was filled in with millions of cubic feet of trucked-in dirt and the elevation of the entire site was raised about 5 feet. Stores, offices, parking lots, roads and sidewalks have been built and the empty fields that once stored floodwater from Bear Creek now contribute to the run-off that flows into the creek. Even more of the flood plain was filled when the Bear Creek Parkway was built around the perimeter of the mall.

Upstream along Bear Creek and Evans Creek, new developments have dumped their overflow runoff into tributaries and storm channels that drain directly to the creeks. The creeks now overflow their banks when the valley gets more than 2 inches of rain in a day. The Keller Farm fields between Avondale and Union Hill Roads regularly flood with storm water from upstream. With the extra floodwater from upstream and the flood plain north of Bear Creek filled and built up, the floodwaters from Bear Creek fill the entire channel between the Bear Creek Parkway and SR520. During the December 3, 2007 storm, the floodwater was within 3 feet of the shoulder of the westbound lanes of 520!

There is way too much water flowing through a channel that has been narrowed by the Town Center development on the north side of the creek. And the Washington Department of Transportation (WSDOT)wants to reduce the channel and floodway on the south side of the creek even more by adding four more lanes to 520. The new lanes will extend 40 feet north of the westbound shoulder where floodwaters gush whenever we get a major storm. Untreated run-off from the new lanes will be washed directly into Bear Creek during major storm events. Salmon depend on this channel to get to their highly productive spawning beds upstream in Bear Creek, Evans Creek and Cottage Lake Creek. Narrowing the floodway with the new lanes could also cause severe flooding upstream especially near the Bear Creek Shopping Center and along Redmond Way.

The SR520 expansion plan was approved in 1992. Since then, a lot has changed in Redmond and the Department of Transportation’s plans for 520 and Bear Creek have become obsolete. Maybe it’s time for a new plan – for the sake of the salmon and the city.

[Historic Bear Creek flood plain boundary drawn from the 1992 Environmental Impact Statement (EIS) for SR520, Figure 3-8: FLOOD PLAIN AND FLOODWAY BOUNDARIES, p. 3-47 and from the Flood Insurance Rate Map (FIRM) Parcel 390 of 1725, Map #53033C0390G, March 30, 1998.]

Bob Yoder
Susan Wilkins, co-author