Tuesday, March 7, 2023

1973 400mw Dworshak Dam on Clearwater River near Ahsahka, ID

(Satellite)

USACE
"Dworshak Dam has one 220-megawatt turbine unit that is the largest hydroelectric generator in the USACE inventory. The other two units are 90-megawatt, for a total project generating capacity of 400 megawatts."
At 717', it is the third tallest dam in the US. The length is 3,287 with a spillway capacity of 180 kcfs and a hydraulic capacity of 10.5 kcfs.
Because it is too tall for a fish ladder, the USACE constructed a fish hatchery just below the dam.
"Dworshak is operated to benefit salmon and steelhead in the Snake River by releasing cool water from the reservoir during the warm summer months. Water is drawn from various depths in the reservoir to adjust the temperature, which typically ranges from 46°–48°F.
"Wildlife mitigation lands are managed to offset habitat losses that occurred when the reservoir filled. About 7,000 acres are managed specifically for habitat for the Rocky Mountain elk."

Evidently the units have been upgraded because this shows a capacity of 459mw.
Andy Michel posted

WorldAtlas-top7 (source).
Dworshak Dam Concrete Gravity North Fork Clearwater River Idaho.
It has "the tallest non-curved concrete face in the Western Hemisphere."

USACE via cbr 
The dam was designed for six bays, but units 4-6 were deauthorized in the 1990s.
via WorldAtlas-dam
"Supporters of the Dam would cite the horrific 1948 flooding of the Clearwater River as the main reason the Dam was needed....The Dworshak Dam was named after Senator Henry Dworshak of Idaho, who was crucial in gaining approval for the project."

USACE-Feb 2, 2023 (source)
"The U.S. Army Corps of Engineers-Dworshak Project is announcing that Dent Acres Campground will be closed for camping between August 1 and September 30, 2023, due to a repaving project."

"Dworshak Dam Project 81 (Batch plant)", Dworshak Dam Collection, Digital Initiatives, University of Idaho Library via uidaho, 1 of 215 photos
Photo taken May 1968. 
"Shows top of the batch plant where they mixed the concrete. Note on reverse reads 'Note one of the cable towers at the extreme downstream end of the track. This would indicate that they were placing concrete on the very downstream edge of the dam. Also seen is some of the crushed rock used for concrete -- the long tubes carries fly ash, a cement ingredient from Chicago that sets the concrete and makes it harder.'"
[I've been wondering where we are going to get fly ash for concrete after they close all of the coal-fired power plants.]

"Dworshak Dam Project 100 (dam base)", Dworshak Dam Collection, Digital Initiatives, University of Idaho Library via uidaho, 1 of 215 photos
1969 photo looking upstream

budowle
"Dworshak barrage is the fourth largest dam in the US and 25 in the world. It is also the highest dam with a straight axis in the northern hemisphere."

It made another "top 7" list of dams.
TataAndHoward
 "Building the highest straight axis gravity dam in the Western Hemisphere, on a river with a mean flow of 5,000 cubic feet per second, at a cost of $312 million, in the name of flood-control, is the second-funniest joke in Idaho. The funniest joke is inside the visitor center: a government sign entreats, ‘…help protect this delicate environment for future generations.’ The North Fork of the Clearwater was an exceptional river with a preeminent run of steelhead trout, and the drainage contained thousands of elk and white-tail deer. The Army Corps of Engineers proceeded to destroy the river, habitat, and fish; then acquired 5,000 acres for elk management and spent $21 million to build the largest steelhead hatchery in the world, maintaining at a cost of $1 million dollars a year what nature had provided for nothing."
[The low flow of 5 kcfs is probably why they didn't build a powerhouse for the remaining three generator bays.]

nwesi

2 of the photos posted by Andy Michel with the comment: "717 feet [219m] high and 3rd tallest dam in the United States!!"
a

b

U.S. Forest Service - Nez Perce-Clearwater National Forests posted four photos with the comment:
56 Years Ago Today [Jun 22, 2024]: Dworshak dam Construction Begins
On this day in 1968, the first bucket of concrete was placed at the Dworshak Dam. The dam, built for flood control purposes after a devastating 1948  flood in which the North Fork increased to 11 times its normal flow, would rise to become the third highest dam in North America. Its construction would last five years, providing many jobs for local residents.
The dam provides excellent recreation opportunities, but is not without its drawbacks. Built without fish ladders, the dam significantly impacted anadromous fish migration, leading to the construction of the nearby Dworshak national Fish Hatchery, which releases over 3 million juvenile fish into the Clearwater River annually. Additionally, construction of Dworshak and its attendant reservoir (Dworshak Lake) led to the loss of winter Elk habitat, which the US Army Corps of Engineers, who built the dam, accounted for by purchasing and managing 9,100 acres of nearby land for elk winter range.
Today, Dworshak not only provides flood control but also for recreation. Boat ramps enable recreators to take to the water to jet ski or enjoy its placid waters. A network of hiking trails provide a wide variety of possible hikes or camping opportunities. Fisherman can cast at numerous lakeside areas and hunters can enjoy the forested land that is a part of Dworshak.
Gretta Hodapp: It needs to be recognized as one of the most dangerous dams in America. Patched cracks, continuous cement reinforcement needs, badly leaking where it connects to the bedrock. Its installation killed an amazing steelhead run, rafting rapids. And destroyed some of the best elk overwintering valleys we had. Its full for one month a year and looks like a drained dirty bathtub the rest of the time. The dam got a c safety rating over a decade ago. One of the worst. But then the army corps changed the evaluation metrics and gave themselves a b rating. Thus getting rid of the possibility of dam decommissioning. Wish I couldve done that for my grades in school. One more even minor earthquake and that dam poses an extraordinary danger for everyone downstream. It doesn't even produce much hydroelectric because the resevoir is drawn down most of the year. They say its to help the salmonid smolts out-migrate. But I have a hunch it's also to help relieve water pressure on the dam for most of the year to keep it from cracking more. It has my vote for dumbest dam in the states. I vote boo.
Andy Michel shared
1

2

3
Denny Greene: Three lines with 8 yard buckets and cooling tubes between each lift I was working there when we hit the one million yards. A month later I was Drafted for Vietnam. Returned in early 1972 Dworshak was nearing completion so I went to work on Lower Granite.

4

Fish Man commented on the above post
The construction of Dworshak dam substantially reduced the distribution of anadromous fish in Idaho, as depicted in this map…

No comments:

Post a Comment