Photo Credit: Aerial of Boundary Dam, 1991. Image 130648, ImageBank Digital Photographs (Record Series 0207-01)
The dam is 340' (103.6m) tall. The turbine hall was carved out of the rock on the right side of the above photo behind the six portals."The eggshell-like double curve of the dam's thin arch achieves great strength with exceptionally low mass. The concrete ranges from 32 feet thick at the base to only 8 feet thick at the crest." The six units have been upgraded over the years so the dam now has a capacity of 1,117.4mw. "Currently, Boundary Dam generates up to 35 percent of Seattle’s energy needs."
Plan of Boundary Dam and Power Plant, 1967
Progress Report, February 28, 1967, Record Series 1201-11
Boundary Dam machine hall, June 27, 2004
Item 151247, Record Series 1204-19
500,000 cu. yd. of limestone was removed to create a cavern that is 477' (145.4m) long x 76' (23.2m) wide x 170' (51.8m) deep.
A million cu. yd. of rock was excavated to create the forebay. [Seattle]
Aerial view looking downstream, showing forebay, trashracks and dam, August 28, 1966
Item 183461, Record Series 1204-01
[At the bottom near the middle is the opening to the diversion tunnel.]
Aerial of Boundary Dam spilling, 1991
Item 130648, Record Series 0207-01
"Spillways cut into the rock are oriented in such a way that full-capacity discharges from both will meet in mid-air to dissipate the falling-water energy that might otherwise erode canyon walls. The spillways have a combined capacity of 108,000 cubic feet per second."
|Harold Coleman, May 2020|
Boundary Dam spilling, Nov. 6, 1998, Item 149513, Record Series 0207-01
[I wonder what the smaller spillway is for. This photo taught me that the purpose of the portals is to allow the exit of the high-tension power lines.]
|1:21 video @ 1:15|
Another license was issued in Mar 2013 because the original license had expired in Sep 2011. The new license is valid for 42 years. The voltage of the transmission lines is 230kV. [nsenergy]
This history provides more details about the legal issues that had to be resolved before construction could begin.
Comments on this post is what motivated the research of this dam. Some comments speculated that it was the Boundary Dam. But the turbine hall photo shows that this is a different dam.
|Tavis Bender posted|
Rotor pull at work today 240 ton 75 mw. Hasn't been out in 40 years. Alot of operators go through a whole career and never get the experience. I'd like to say where but really can't. Cool
Rob Jordan: High Speed Unit
Travis Bender: Rob Jordan 400 rpm.
I didn't like this video, it is raw footage and they had two 15-sec ads at the beginning.
|14:31 video @ 1:11|
Construction of Boundary Dam Part 2, 1965-1967
I did push the slider across the next video. If they edited the footage of the five videos down to one, I think they could have an interesting video. It sounds like a good student or intern job.
|14:31 video @ 11:40|
Construction of Boundary Dam Part 3, 1965-1967