1906-2018 Bloede Dam near Ellicott City had a hidden power plant

(Satellite)

This dam was downstream of the mill town Ellicott City.

F Guidry, Jan 2018

Matt Pyle posted six photos with the comment: "Its been a bit so I figured I'd drop something interesting in. Bloedes dam out here on the east coast used to be in MD.  Odd plant with everything under the spillway.  A normal powerhouse is fine, but I am not sure I want the river running over me."

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Dennis DeBruler commented on Matt's post
The dam was built in 1906 and quit generating power in 1924. It was removed in 2018,
https://www.chesapeakebaymagazine.com/video-bloede-dam-blast-to-reopen-important-habitat/

"Bloede Dam was the first underwater hydroelectric dam in the world, made possible by the hollow construction of the reinforced concrete slab and buttress dam." It was built in 1906 and removed in 2018. [hydroreform] (I left feedback that they indicate the dam was removed in 2018 but they show the status as active. Let's see if I remember to check back to see if it gets fixed.)

CheasapeakeBayMagazine
Bloede Dam Blast To Reopen Important Habitat
[This page had links to the following two videos.]

0:29 video @ 0:28

Not only did the dam block fish migration, it was an "attractive nuisance" in the Patapsco Valley State Park.

2:38 video @ 1:48
 Here is the bridge shown in the video.

AmericanRivers
It generated power for less than two decades because it went dormant in 1924. $1.5m was invested in 1992 to build a fish ladder. It would require $1m in repairs to comply with Maryland dam safety requirements.
"Historically, river herring (blueback herring and alewife, collectively) and American shad were a major fishery resource throughout the Chesapeake Bay and a common food staple for Native American tribes. The commercial harvest for American shad peaked in 1890 when landings in Maryland exceeded seven million pounds. Unfortunately, the absence of policies to manage this fishery resource at the time contributed to the rise in commercial exploitation of American shad and river herring, not only in the Bay, but also along the entire Atlantic seaboard. As a result, river herring and American shad landings began a precipitous decline. By 1979, these fisheries were near collapse, as evidenced by only 18,000 pounds in American shad landings in Maryland." The fish ladder did not help. The 34' (10.4m) high by 220' (67m) long dam is also a serious public safety hazard. There have been at least nine dam-related deaths since the 1980s.
[NOAA specifies the height as 26' (11m).]

AmericanRivers
Because two other dams have been removed, the removal of this dam will add more than 65 miles (105km) of spawning habitat for river herring and create 183 miles (295m) of open river for the American eel. This will improve the health of the Chesapeake Bay ecosystem.

noaa_removal
The removal restores spawning habitat for "blueback herring, alewife, American shad, hickory shade and American eel."

 

noaa_removal

noaa_retrospective
Unlike fish ladders, dam removal has realized the hoped for improvement of the fish populations.