Landslide shifting as Sunset Falls project looms

As the Snohomish County Public Utility District continues to study the feasibility of the Sunset Falls Fish Passage and Energy Project, the landslide directly south of Sunset Falls continues to shift, change and move.  

Located south of the town of Index in the Mount Index Riversites neighborhood, the hydroelectric project proposed for Sunset Falls would reroute water from the south fork of the Skykomish River, sending it through a roughly 2,200-foot subterranean tunnel to a semi-underground powerhouse at the base of Sunset Falls. The horseshoe-shaped tunnel would extend for 800 feet at a 22-foot diameter and another 1,400 feet at a diameter of 21.5 feet. The tunnel would be constructed using controlled dynamite charges, which is concerning to nearby property owners.

Residents who live in the area feel the instability of the region should preclude such a proposal. The hillside directly south of Sunset Falls started sliding in December 2013 and has been moving ever since. Mt. Index River Road, the small private roadway that formerly wound through the area, is completely unrecognizable and impassable. 

A cement Jersey barrier hangs in limbo, stuck in the muck and jutting precariously out over the river. 

It’s been ongoing for close to three years, and only one thing about the slide has remained constant: it’s never completely still.    

There are striking differences in the way the hillside looked last week, in comparison to what it looked like in April. In April, the entire scene looked like a moonscape; the face was solid grey and covered over by an unstable and unpredictable layer of quicksand-like muck. Now, there is foliage growing from the root balls of felled trees, large rocks have begun to collect in concentrated locations and the ground is sprinkled with weeds, including grasses and horsetails, which are indicative of moisture.

Last week the ground was firmer and less treacherous than six months ago, however, clumps of dirt could be seen tumbling from one of the highest points of the upper scarp.   

Roughly three-quarters of the way up the slide, a constant flow of water streams out from multiple locations, seeming to come from inside the hill. The rivulets of water have begun to carve out pronounced ravines that travel down the face of the slide that weren’t there in April. 

Objects left behind by evacuated homeowners have continued to move down the hill, crawling slowly towards the base of Sunset Falls.

The constant release of water from the slide has led residents of the area to speculate that the river is rerouting itself, reclaiming an old course.  

Project opponents who wanted to remind commissioners that the slide still exists and it doesn’t appear to be going anywhere brought up the landslide during a recent PUD Commission meeting. Additionally, there has been another major landslide event southwest of the Sunset Falls landslide, which is negatively impacting Bridal Veil Creek.  

Opponents have asserted that because of the landslide, Sunset Falls no longer meets PUD’s own criteria for locating new hydroelectric projects. A total of seven criteria were outlined in PUD’s 2013 Pre-Application Document submitted to the Federal Energy Regulatory Commission (FERC), the federal agency tasked with approving new hydro projects. One of the criteria stipulates that areas of consideration should have “no known geological hazards or unstable areas that would preclude construction.”

The Snohomish County Planning and Development Services Department is actively monitoring the landslide. Earlier in the year, they considered the possibility that the river could be rerouting itself, but quickly reevaluated that assessment. The department’s position remains unchanged.  

“Experts who have visited the site have not concluded that the river is rerouting into the slide area at this time,” states the PDS department. “Snohomish County will continue to periodically monitor the site for changes. We would also recommend property owners in the area notify Snohomish County if any changes to the current conditions occur.”