Chelan PUD Monitoring Chelan Gorge Slope

The slope along 1,200 feet of Reach 2 in the Chelan River Gorge is being closely monitored Chelan County Public Utility (PUD) staff reported to commissioners at Monday’s board meeting. One location, Site A (see map), is a known area of ground movement. The PUD has been watching this area for more than 25 years with little activity. It’s located about 750 feet from the Gorge Road.

Site B is a more recent movement area. Chelan PUD employees were scouting the area with Chelan-area residents to identify potential locations for extending the Reach 1 trail. What looked to be an old road was actually a newly formed striation or furrowed ground at the north end of the PUD property. On closer examination, it was obvious that there had been a slide area just below Site B and it traveled down to the river shoreline.

Bill Christman, PUD Chief Dam Safety Engineer, said PUD staff has determined this new location seems to be more active than Site A. This earth movement is natural phenomena. Out of precaution, the area is being closed off to public access and signs will be set up to make the public aware of the potential hazard.

The PUD is contracting with a geotechnical firm to help with the assessment. PUD staff and the consulting engineers will look at what might occur if an earthen dam resulted from a large rockfall. Also to be studied is what impact an earthen dam would have on hydro operations, as well as conditions further downstream in Reach 4. Likely, there would be a large release of water below the dam, similar to what occurred in the 1990s, leaving sand and gravel in Reach 4 on its way to the Columbia River.

Until more information is known, the public is urged to stay out of the signed area. Christman went on to say that there are no structures in the path of the unstable ground. While it is possible a large ground movement could release material that could block the gorge, the gradual nature of the ground movement makes it unlikely that there would be a large release that could block the gorge.

No protected fish travel to Reach 2. There are resident fish in the area. If there was a greater slide release into the river, a potential response might be to increase flow into the Chelan River from the Chelan Dam to create a “flushing” action to push the debris downstream, similar to what would naturally occur. The PUD would monitor this action carefully to protect listed species in Reach 4 and to minimize water quality impacts.

The PUD has reached out to state and federal agencies, stakeholders and tribes to advise them of the situation. All those who have been contacted agree with the approach being taken by the PUD.