Engineering/Dam Removal – Barnard Construction Co.

Dan and Aaron from Barnard Construction are giving an update on the deconstruction of the dams, starting with the Elwha Dam.

The Elwha Dam included a gravity dam, penstock, powerhouse and floodgates, plus a walkway allowing workers to walk across the dam. The logboom kept logs out that would come through at  high water, which would be sent through the floodgates so not to block up flow.

On Sept. 19, 2011, an excavator with a hydrolic hammer came in and starting hammering away at the structure. They started on the east side of the dam (right spillway). They were creating a spot to divert the water to help with deconstruction. Another diversion was created later, using rocks and concrete to control the water flow from the reservoir.

An overhead shot shows the railcart bridge that allowed access for construction workers to various parts of the dam while working around water channels.

Left spillway (west side) were hammered away, with debris being put into trucks that hauled it all away.

Once all the piers and gates were removed, there was a concrete base to work on, which they blasted away and also to use later as another diversion channel.  Nine total diversions were created back and forth across the old dam to get the water level down so could work on dam removal.

Powerhouse was gutted and then the structure was removed. Search tank was taken down and removed. Powerhouse was finally removed, and the reservior elevation was down to 140 feet. After riprap was placed where the powerhouse used to be, crews started rebuilding the area as a hillside.

March 9, gravity dam demoiltion was completed. The coffer dam was removed and the river was able to flow through its original channel. Crews continued to excavate the channel to help rebuild the hillside.

Today, where the dam used to be is a large hillside covered in straw for erosion protection.

Glines Dam Canyon update:

Used to be: Arch dam, left spillway, thrustlock, intake from the reservoir to the gatehouse through the hill and turned into a penstock and to the surge tower and to the powerhouse.

At Glines, started with a excavator on a barge hammering on the wall, breaking off concrete and let it fall to the toe of the dam.

Excavator working on dam, the crews had to navigate around rocks, logs and other parts of the dam structure.

Water had to go through the spillway before crews had the dam lowered enough to send water through the deconstructed part of the arch dam. Water were passed through notches created in the dam.

First drilling and blasting scenario was in the snow.

Powerhouse demolition included gutting the innards, with major equipment used to take apart the insides. Equipment and hardware and transmissions were recycled. A few items were donated to local museums, but anything with monetary value was recycled.

Aug 1, 2012 – started the fish window, so blasting has been put on hold until end of September.

Question: How does this compare to other projects you do?

THis is our first entire dam removal we’ve done. We’re usually doing dam modifications.

From the Internet: What’s happening to the dam rubble being removed? Being sent to a gravel pit, where it will be crushed and used as road material.

 

 

 

 

 

This entry was posted in Uncategorized. Bookmark the permalink.