Condit Dam Timelapse Update: Buildup to Breach

Our two timelapse cameras have now been shooting 10 images a day for the last 67 days.  With more than 1,200 images in the can, we thought it was time to let everyone see how the project is developing.

(tip: click the little arrows and make it full screen)

So, what’s happened since we installed our cameras?  Here’s what you can see in the first video:

  • The lake was drawn down more than 10 feet
  • The minimum flow has been diverted around the site, and the pool below the dam has been drained
  • A scaffolding was installed to allow better access to the site
  • Cables were strung high across across the river and machinery lowered into the riverbed
  • A huge floating crane has been moved into position upstream of the dam
  • Blasting of the drain tunnel is progressing well
The final countdown to breach day: October 26th, 2011 has begun.  If you’re wondering, no, there won’t be a way for you to watch the blast in person (I was wondering).  Access will be restricted on both sides of the river.  There’s rumors of security planned for the west shoreline and the NW Lake Community access is private property, so be respectful.  Fortunately, PacifiCorp will be live-streaming the breach via the Internet, so you’ll be able to watch it from home.  More details on that to come.
Cheers to a soon-to-be freeflowing White Salmon River!

Condit Dam History – Part 6

The total workforce employed by Stone and Webster of Boston Massachusetts (Northwestern Electric Company’s contractor) averaged 900 men during the 11 months required to build the Condit dam and powerhouse. Most of the men were recent Greek immigrants, having been contracted through an employment firm in Portland, OR.

After diverting the river’s flow, the next major step in dam construction involved preparing the river channel for pouring of the dam foundation. This highly illustrative photo shows important components of this work, including survey of river channel, using high pressure water jets to wash sediment from the bedrock channel, and hoisting of resulting debris from the canyon for disposal. Meticulous cleaning of the dam’s foundation was absolutely critical to preventing water leakage below and through the dam, which could cause subsequent erosion and dam failure.

Up to 12 feet of alluvium (i.e., river rock) had to be removed from the original river bed before reaching stable bedrock. By all accounts, an excellent job was accomplished by Stone and Webster. The integrity of the dam’s concrete and foundation are still excellent today

Above is a downstream view of the dam site.  The photo below shows an upstream view… both taken 99 years ago.  Remember that you can click on any of the images in this blog for a larger view.

Condit Dam Removal Update #3

A routine camera download from the two time-lapse stations was accomplished last Saturday (17Sep11).  Progress observed at the deconstruction site was significant, with tunneling approaching the 40 foot mark (almost half way toward the upstream target at the dam’s face).  The photo above shows a first view of the tunnel site.  This tunnel will be used to breach the dam in late October, and allow flushing the entire reservoir volume (and the majority of the accumulated sediments) from the upstream reservoir (soon to be canyon), in six hours, at a rate of 10,000 cubic feet per second.  This will be the first time that this method of dam removal has been employed… and historic in many respects. 

Note the steel mesh blanket above the tunnel, which is draped over the opening during blasts to prevent fly-rock.  This is a very important consideration, since one of the two deaths occurring during original construction in 1912-13 was consequent to a worker being struck in the head by a flying rock.  The tunnel is being excavated on the far eastern edge of “Cameron Canyon”, and the native basalt contact is readily visible on the right of the tunnel bore. 

As previously mentioned, all equipment is being delivered to the canyon using a cable yarding system.  This same system is being used to “fly-out” all resulting concrete and steel debris in a large aerial bucket.  The photo above shows the cable anchors and blocks used to affix the yarding cable on the west wall of the canyon.  This attachment point is along the “goat trail” being used by the authors to access time-lapse Station 1. 

Finally, another major activity occurring Saturday was mobilization of the floating crane near the upstream face of the dam.  Soon, the crane will be used to dredge sediment and logs from the base of the reservoir to allow free and rapid draining of the reservoir in October.

Condit Dam History – Part 5

This May 28, 1912 scene shows the White Salmon River banks shortly before being merged by Condit Dam, and first phase of dam building at the Cameron Bridge site.  If the current dam was transposed onto this photo, the reservoir drain tunnel would be in the center of this image, and its course would follow upstream along the bottom of the river channel.  And too, the canyon that re-emerges from the concrete next summer will look similar to what is shown.   

On the left, workers are in the process of boring one of three tunnel segments needed to divert the river’s flow around the dam site during construction. This tunnel opening is still visible today.  Without diversion and the utilization of mining technology to construct the tunnels, building Condit would have been impossible.  In many respects, this work phase (constructing a diversion tunnel to provide a dry environment for building the dam), is analogous in reverse to happenings today (boring a tunnel to drain the reservoir and allowing deconstruction in a dry environment).  Almost 100 years later, construction has intersected deconstruction (see the last post).

Two months later (August 3, 1912), this photo shows the Cameron Bridge dam site from upstream, and the canyon topography we expect to see after the dam is breached in late October 2011.  Illustrated here is construction of the rock-filled crib dam used to divert the river into the three diversion tunnels and connecting wood flumes, which are visible on the west bank.  Once diversion was completed and the river re-routed, actual dam construction began. 

(Note that time-lapse Station 2, being monitored and reported on during this project, is located just upstream of this view, along what’s currently the west shoreline of the reservoir at Cypher’s cabin.  This crib dam should be visible after the October flush, along with the Jaws river canyon).

Condit Dam Removal Update #2

Drilling and blasting on the 90 foot long drain tunnel began on the morning of Thursday, September 1, 2011.  This shot taken from time-lapse Station 1 (below dam on the west shore) shows Kiewit’s small excavator and dozer that will be used to remove tunnel debris after each blast.  Behind the platform (visible on the right side of the dam’s base) workers are using air-powered rock drills to bore the array of holes for loading explosives and blasting. 

Meanwhile, a marine construction  subcontracor was busy at the east shore boat ramp, building a large barge with mounted crane.  The barge will be towed across the reservoir to the face of the dam using the pictured tug, to begin removing sediment and logs from the upstream face of the dam (i.e., bottom of reservoir that will be intersected by the 90 foot drain tunnel, via a final blast scheduled for late October 2011).