Flood Control Zone District

No 1 Canyon Debris Basins

No 1 Canyon Debris Basins

(PHOTO: 2015 photo of the first debris basin project in No. 1 Canyon.)

 

Project Description

Located immediately west of Wenatchee, the No. 1 Canyon basin sits along the east slopes of the Cascade Mountain foothills. The canyon’s natural drainage system has a long history of experiencing occasional heavy runoff – and even debris and mud flows. But these flows, typically caused by high intensity storms, have grown more destructive as the Wenatchee community’s urban area has grown. When these flows leave the basin’s natural channel, they flow into existing residential developments, the City of Wenatchee’s stormwater system and, at times, the Columbia and Wenatchee rivers.

A consultant for the Chelan County Flood Control Zone District is designing a series of four flood debris basins on 21 acres at the end of No. 1 Canyon Road that will capture and release flood flows downstream in an attempt to minimize future damage. When built, the project will allow sediment, woody debris, rocks and other materials to be deposited within the basins and overflow channels before the material is conveyed downstream and, potentially, causes a system failure. The project’s design is now nearly complete.

On a much smaller scale, a similar series of detention basins was built in 2015 further down No. 1 Canyon Road, at milepost 2.6. Over the last five years, it has proven to decrease the amount of sediment entering the City of Wenatchee's stormwater system, with the sediment being replaced with an increase in the volume of water.

Preliminary Plan Sheets

Project Vicinity Map

Photo Page: 2015 Project

 

Project Benefits

Numerous studies of the No. 1 Canyon drainage conclude that some type of debris basin facility is needed to detain and release flood flow in a controlled manner. By building the four flood debris basins, Chelan County is trying to be proactive. At this time, the county and property owners are acting in a reactionary way; when a flooding event occurs, county crews and private homeowners clean up the aftermath. This proposed approach will be a step in minimizing future disturbances and hazards.

The project should reduce the chance of potential flooding, require less maintenance (material would be retained in one location rather than throughout the basin or on roads), and allow the already established stormwater system to work at a higher capacity because of less debris and sedimentation in the urbanized system.

 

Construction Schedule

Construction on the basins has been pushed back to summer 2022. When construction starts, property owners will see three months of active work.

During construction, neighbors can expect an increase in heavy truck traffic. Some 10,000 cubic yards of dirt will be removed from the site and about 400 loads of rock will be brought in to line the basins and channels.

Because the roadway will not be closed, there should be minimal impact on services, such as garbage and delivery services. We will contact emergency services as well as Waste Management and the Wenatchee branch of the U.S. Post Office to alert them to the construction project.

 

Funding

The construction portion of the project will cost about $1.3 million. It will be paid for with a nearly $1 million grant from FEMA and with money from the FCZD.

 

Questions?

Please submit any questions or comments to FCZD@co.chelan.wa.us. Or you can call our public information officer, Jill FitzSimmons, at 667-6415. You can also sign up for the FCZD e-updates so project updates are sent to you via email. 

 

Frequently Asked Questions

No. There is no need for road closures because the basins are being built on property the county purchased for this project.

The biggest traffic impact will be the increase in truck traffic for about three months. Property owners will see heavy truck traffic as trucks not only haul out about 10,000 cubic yards of dirt but also bring in 400 loads of rock needed to build the debris basins. Minor traffic delays may occur with the increase in truck traffic. At times, flaggers may be needed to direct trafic. Construction has been moved to summer 2022.

The debris basins are manmade but natural, earthen structures that use rock and natural vegetation. To see a similar but smaller project, drive by the series of basins completed by Chelan County in 2015 that are closer to the Wenatchee city limits, at milepost 2.6. The new project will have four basins that are connected by an overflow channel and weirs. So when snowmelt or sudden rains overflow the No. 1 Canyon drainage, the water will progressively fill each of the four manmade basins, slowing down the water and depositing sediment and debris into the basins. After the water recedes in the basins, the debris will be cleaned out.

The Chelan County Flood Control Zone District will be tasked with the maintenance of the basins.

If you have questions or concerns, contact Chelan County Public Works public information officer Jill FitzSimmons at 667-6415 or jill.fitzsimmons@co.chelan.wa.us.

Posted: 07/30/2020 02:24 PM
Last Updated: 03/03/2021 10:52 AM

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