Thursday, May 7, 2020

McNary Dam on the Columbia River near Umatilla, OR


I'm saving a satellite image because the flow appears to be so strong.
3D Satellite
But none of the gates are up! So I'm confused. More on this later.
3D Satellite
The dam was built between 1947 and 1954. All of the power units were operational by Feb 1957. [ColumbiaRiverImages] The dam covers the Umatilla RapidsLewis and Clark referred to them as "Muscle Shell Rapid."

USACE via ColumbiaBasinResearch

Powerhouse Capacity:
Nameplate capacity: 14 @ 70 MW, 980 MW total
Overload capacity: 14 @ 80.5 MW, 1127 MW total
Station service units: 2 @ 3 MW, 6 MW total
Hydraulic capacity: 232 kcfs
This is a rare example of a hydroelectric power plant that can produce as much power as a modern coal-fired plant, about a gigawatt. Note that its 232 kcsfs flow to achieve a gigawatt is more than the 160 kcfs record flow through the spillway of the Oahe Dam. In fact, that is more than the flow that tore up the spillway of the Oroville Dam. The McNary Dam produced 5.27 gigawatt hours in 2015. Since there are 8,760 hours in a year, that is an average of just 600kw. That is less than 0.1% of its advertised capacity. So I assume this dam is used as a peaking power plant. That is an advantage of a hydroelectric plant because increasing the output is just a matter of opening some gates a little  further. In contrast, a coal fired power plant can consistently produce its nameplate capacity. In fact, they need to produce a rather constant output. It takes a while to "heat them up." The Kaplan turbines have a 280" runner, rotate at 85.7 rpm and are rated for 95,400 horsepower. [USACE]

This satellite image shows the lower gates, which are "arch gates." I looked closely after reading about an arch gate in the specifications. This is the first time I have seen an arch gate. I presume they keep the lock full between tows to relive the stress of a 75' head on the miter gate on the upstream side. The dimensions of 86' x 683' are weird in my Midwestern experience. I'm used to locks being 110' wide and either 600 or 1200 feet long. Do they have a different barge size standard in the Northwest?

The structure at the bottom of the arch gate image is one of the two fish ladders.
3D Satellite

This is the fourth dam on the lower Columbia River (Bonneville, The Dalles, John Day and McNary) and it is 293 miles from and 344' above the mouth at Astoria, OR. [UnionBulletin]

This photo allows me to understand how the gates of the Kentucky Dam work. They use a powerful gantry crane to lift the sluice gates and let the water free fall onto a spillway apron. A Tainter gate reduces the force needed to lift the gate at the expense of larger gate abutments to hold the shafts of the Tainter gates. And with 22 50' x 51' gates it is easy to fine tune the flow by varying the number of gates that are open. Speaking of the force needed to lift the sluice gates, the capacity of the two deck cranes is 200 tons. [USACE]
thebbz via Bridge Hunter, Photo taken by Derrek Stewart
Derrek's photo helps explain what looked like a large flow in the above satellite photo because of all of the white turbulence. Somehow they have gates near the bottom of the spillway. The USACE photo at the top caught the dam with all of the gates closed. The USACE photo above from Columbia Basin Research and the satellite photo shows them all open. The research photo is like the above one, a couple of the main gates are completely open. And the following photo is another example of all of the lower gates being open with two additional main gates. The reason they open the main gates next to the powerhouse is to keep the more turbulent flow as far as possible away from the shipping lane, which would be over at the lock side. I assume the flow from near the bottom has something to do with fish management and/or water temperature control because the above photo shows that a main gate can be partially lifted for a small flow.
Travis Stoltenberg, Jun 2017
I tried using Google Earth to get more data points concerning the gate usage, but I got reminded that Washington State has a lot of cloud cover. I found only one photo that was not a photo of clouds!

Should that 1894 date be 1994?
I was really impressed by the 2.2 mcfs until I realized that this dam is more of a run-of-river dam than a reservoir dam. I wonder what the cfs on the Ohio River is when it is in flood stage.

It appears they are finally upgrading the powerhouse from 1950s technology to the 21st Century. I wonder what the ratings will be for the new equipment. It is disappointing that I didn't see anything about this upgrade on the USACE site other than they are working with the Bonneville Power Authority to develop an upgrade plan for the region. All those rocks in the foreground made me notice that they have completely drained the reservoir pool!
Bradford Needham, Aug 2017

When they built the Oahe Dam, they simply drowned the towns and farms of the people, mostly Native Americans, who had lived on the land. When they built the St. Lawrence Seaway, they moved some of the towns. When they built this dam, the USACE built levees along the three towns upstream of the Snake River.
The cities of Pasco, Kennewick, and Richland, Wash. are surrounded by 16.8 miles of levees. Drainage and groundwater levels landward of these levees are controlled by 15 pumping plants.
Street View

Street View

I don't normally use exclamation marks, but I noticed I used them three times in these notes.

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