| November 16, 2000
News Release As autumn rains saturate King County, chronic landslides have created a threat to public safety on an unstable slope above Garrison Creek in Kent. That's why the King County Department of Natural Resources is now knee deep in a project to stabilize the slope and stop the slides. After dumping as much as 30,000 cubic yards of sediment and choking the creek over the last 11 years, the landslides have worsened to the point that erosion threatens 216th Street and building sediment threatens a bridge at 218th Street. "Quick action before the rainy season was very important in this case," said Nancy Hansen, division manager of the county Water and Land Resources Division. "A washout, particularly at night, would endanger the lives of drivers on these roads." To stop rain from saturating the eroding slope and causing landslides, the response by the Water and Land Resources Division involves installing a 60-inch, 15-foot deep catch basin atop a steep ravine that will drain a 40-acre area. The catch basin will route water to the bottom of the slope with 400 feet of 24-inch diameter high-density polyethylene pipe. At the bottom of the pipe is an energy dissipater, which essentially is an engineered collecting box that will slow high velocity (up to 25 mph) water down to a non-erosive flow, drain it out the top and into the creek. Construction work began last Wednesday and is scheduled to finish in about two weeks. Cost of the project is estimated at $150,000. The county is saving money by repairing the damaged site with surplus fill dirt from other King County projects nearby. The crews have been careful to ensure the project is salmon friendly and have salvaged native plants for use in county salmon restoration projects. Areas disturbed by construction will be replanted. More than six feet of sediment has filled the stream at the bridge, located a mile downstream from where the sediment seeps into the creek. The City of Kent has had to dredge the stream in the past as a temporary fix and to protect a sewer line and two water lines. The city has since elevated the lines. The county's emergency work provides a long-term solution. "The City of Kent appreciates King County's quick response on this major sediment source and will continue to work with the County on a long range program to restore conditions in Garrison Creek" said Bill Wolinski, Manager of Environmental Engineering and Public Works for the City of Kent. "Despite its location in an urbanized area, the stream has great potential to support healthy runs of salmon. This was reinforced when five adult coho salmon appeared at the 218th bridge earlier this week." In addition to working with the City of Kent, the county has also enjoyed excellent cooperation from the private landowners on whose property the project is located. The county provided fir trees that were cut down during the project for the landowners. ... Photo opportunity: County crews are welding together the 24-inch diameter pipe and using heavy equipment to set the 200-foot sections into place within the ravine this week. Contact Media Relations Specialist Logan Harris (206) 263-6550 if you are interested in setting up a picture. Be advised the site is in a ravine -- photographers will need a safety vest, hard hat and boots. On site, you will check in with crew leader Julius Tiangson (206) 296-8509; pager (206) 409-1635.
Office of Emergency Management: Landslides Drainage and Water Quality Complaints
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