Duncan Dam, British Columbia. The dam was built to create a storage reservoir in 1966-67 to supply water into the Columbia River system in winter. It is at it's lowest level in around April. At that time of the year, you can walk out onto the roadbed (the old road that went up alongside the river.) It is on this road that the NW&BIT telephone line used backwards-2 purple ponies.

I got some from a fellow who drove along that road in 1965 after the poles had been dropped. All the trees and buildings were being dropped and burned off in the area below the future waterline. He said he stopped his car and took whatever he could get unscrewed off one pole, and threw them in his trunk. He wound up with 8 backwards-2's and 2 NWBIT's!!!!!!! off of just one pole. This is the Lardeau area where Grant Salzman got ahold of the first known all-horizontal Canadian whithycombes! There was a road and 2 railways in the valley that was flooded.

Here's a good slideshow of the building of the dam:

http://www.virtualmuseum.ca/Exhibitions/Hydro/en/dams/duncan_gallery.php?id=53