1938 Lock and Dam #9 on Allegheny River near Rimer, PA

(Satellite)

I could not find a capacity number for the powerhouse.

"This is the last lock on the Allegheny River and is about 7 miles south of the nominal limit of navigation at Brady, PA.  Built in 1938 this and other structures allows one to navigate a boat or barge from Brady all the way to the Gulf of Mexico." [Jersey Mike's Rail Videos]

USACE
"Allegheny River Lock and Dam 9 is in a caretaker status (IMTS Level 6). It will remain closed indefinitely except for commercial appointment lockages.
"Lock and Dam 9, like all navigation facilities on the Allegheny River, consists of a single lock chamber and a fixed crest dam. This type of dam is basically a concrete weir, or wall, across the river which keeps the river channel upriver of the project deep enough for navigation -- about 9 feet or more.  Water which flows over this type of dam cannot be controlled locally. Consequently, it cannot provide any control over flood waters.  An incidental benefit derived from the pool formed by the dam is the availability of a source of municipal and industrial water."

The spillway is 918' (280m) long with a hydraulic height of 30' (9m) and a structural height of 55' (17m). The lock is 360' (110m) x 56' (17m). [data]

The Allegheny River Development Corp. paid the USACE to operate Locks #6-#9 for recreational use during the Summer of 2023 with this schedule.

They had been closed for recreational use since 2011. [TribLive]

If you follow the Armstrong Trail upstream from here you come to a former Pennsy coaling tower and turntable.

USACE, Pittsburgh District posted five photos with the comment: 

Yo Dudes and Dudettes! We’re taking you back to the times of big hair, synth music, and neon colors, presenting the 1985 Allegheny River Lock and Dam 9. 

These photos were taken at river mile 62.2 near Rimer, Pa., in Armstrong County.   

So, we’re talkin’ about Lock and Dam 9, right, and it’s got this single lock chamber and a radical fixed crest dam, just like all the other navigation hotspots on the gnarly Allegheny River! This dam is basically a concrete weir, or like, a super solid wall, stretchin’ across the river to make sure the water upstream is deep enough for navigation—it’s like 9 feet or more! Cowabunga!

Now, the water that’s crashin’ over this type of dam, ain’t under our control, locally. Total bummer—it’s like, no shield against the surgin’ flood waters! But, dudes, on the flip side, the pool made by the dam is a primo source for municipal and industrial water! Totally radical bodacious incidental benefit, right?! 

Keep it cool and stay tubular!

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0:24 video @ 0:04

4:05 video @ 2:20