Condit Dam Removal Update #5

The timelapse camera at Station 1 below the dam has been woozy since late June, which has required repeated trips to reprogram, change batteries, and just today replace the power converter circuit.  Thanks to Mark at Harbortronics in Ft. Collins, we have new parts installed that will hopefully solve the problem and get things running.

In the meantime, work on both dam removal and restoration of the old reservoir is happening fast.  I figure I’ll use the rest of this cloudy morning in Husum to provide some mid-July progress updates.  Here they are… and remember you can click on images to enlarge…

Two weeks ago I was given the opportunity to cross the dam and go through the  demolition area with Stephen Caruana of Kleinfelder and Associates (prime engineers on the project).  This photo was taken from the west hillside, and shows the ramp that leads to the original wooden flow-line route, where concrete from the demolition is being placed in the trench for later recontouring, retopsoiling and revegetation.  

This second photo was taken today (7-14-12) from Station 1, and shows how much of the dam has been busted, loaded and hauled to the spoils location along the old flow-line route.  I’d hazard a guess that 30% of the dams original height has been reduced so far.  I also noticed that Merit seems to be doing a good job of preventing the broken concrete from entering the river above and below the site.  This picture shows them using three hydraulic excavators (with jackhammer heads) to precisely break the cement into chunks that can be handled by the loaders and off-road dump trucks.  If drilling and blasting methods had been used, the difficulties with containing the broken concrete would have been much higher, and there would have been more likelihood of impacting downstream water quality and aquatic life.  

This third photo shows the White Salmon River immediately downstream of the currently breached dam.  As such, this reach was the first to feel the impact of last October’s (2010) breach.  Surprising is the fact that it has not changed much from the pre-October condition.  Note that turbidity in this section, and in the now exposed reservoir reach, is visually almost back to normal, except during days when the contractor is actively pushing reservoir sedments into the river during regrading operations (see below).  The same thing can’t yet be said for the lower river, where the gradient shallows prior to entering the Bonneville pool.  The lower river’s sediment transporting ability is still adjusting to the high sediment load, although the two are coming close to a balance.

In my way of thinking (as a person who used to earn his buck doing mined land reclamation in the Black Hills of South Dakota), this view of the old reservoir about 1/2 mile above the dam shows the most exciting aspect of the rapid-flush river restoration method employed at Condit.  The Condit rapid-flush method is interesting given that it relies on the power of water stored behind the dam to complete the first and most important phase of restoration, that being the removal and regrading of many of the near shore and low-wall sediments. The success, at least in this reach, is evident at the bottom of the photo, where sloughing of reservoir sediments to the original ground surface has occurred.  Note the 100 year old and well preserved stumps!   Above this level, where hillside gradients are shallower and sediments were more stable, thick terraces of reservoir sediment still remain.  Providing for the long-term stability of these upland terraces (to minimize erosion, sedimentation, and water quality degradation), therefore, came to be recognized as the most important component of restoration surrounding Condit Canyon.  Restoration at Condit (and all other landscape restoration projects) primarily involves “kick-starting” processes that lead to improvements in a) hydrology, b) topography, c) soil mantles, and d) vegetation.  By far, the most important targets for this work are riparian (stream side) areas and hillsides, as opposed to river channels themselves.

The active restoration seen in the background and foreground is bulldozing to regrade the perched sediment veneers back to more stable slope angles.  A small side channel has also been regraded to restore the hydrology, and enable establishment of a permanent plant cover.  Seeding and planting will occur in fall 2012 and spring 2013.  The photo also shows where the company has placed logs salvaged from the reservoir.  Logs were recently placed both horizontally and vertically on the slope, to provide sites for plant germination, shading, colonization by invertebrates, and habitat for cavity nesting birds.  

As a final note… just as PacifiCorp is successfully using very old cable logging technology and local knowledge to accomplish important aspects of the dam removal, it will be vital to use established, time-tested revegetation methods and plant materials for regenerating the forests that once occupied the slopes around the canyon.   Local foresters, natural resource specialists and nurserymen have, for the past 50 years, developed proven methods of reestablishing forests… something that is vital to addressing weed colonization, soil erosion, river sedimentation, loss of stream shade, and insufficient large wood recruitment for fish habitat.  To ensure restoration success, it will be important for the company to put high emphasis on establishing the climax forest vegetation types as quickly as possible, which is something the old-timers found a good method of doing.