1941 Morris Sheppard Dam and Possum Kingdom Lake on Brazos River

(Satellite)

brazos_inspection (source)
"BRA’s largest dam, at 2,700 feet [823m] long and 190 feet [58m] high, or about half a mile long and as tall as a 13-story building."

"The dam consists of nine crest "roof weir" [see more information below] type gates, each approximately 74 feet [22.6m] long and 13 feet [4m] high for the passage of floodwaters. Each gate passes approximately 9,600 cubic feet per second (cfs) of water when open. The Morris Sheppard dam was originally constructed with a hydro electric generating facility that is no longer in use." [brazos_reservoir]

brazos_dam
"At the time, the Morris Sheppard Dam was the tallest flat-slab buttress dam in the United States."

brazos_dam
It was built with two 11.25mw generators, but they quit working in 2007 when safety issues were identified that were deemed too expensive to fix. Decommissioning was not complete until 2014. They had to install a controlled outlet conduit within the dam structure to replace the flow through the removed penstocks.

This photo shows that the new controlled 78" conduit outlet in the lower corner of the powerhouse has a lot more capacity than the three controlled outlets in the body of the spillway. There is also a 42" conduit just this side of the 78" conduit.

brazos_dam

A Google search, after the AI did some "thinking," taught me that a "roof weir" is another name for a bear trap gate. I noticed that they are doing maintenance on two of the nine gates in the above photo. I zoomed in on the closer one. We can see the stop logs holding back the lake while the gate is disassembled. And one of the two leaves of the gate has been removed.

Digitally Zoomed

Has that second gate from the right been broken for over six years?

Santy Lay, Jun 2020

Since one of the gates is actually spilling, not just leaking, water, they have closed all of the outlet conduits.

Santy Lay, Sep 2020

The good news is that no power is needed to open and close a bear trap gate. The weight of the water operates the gates depending on which valves are opened. The bad news is that workers have to go out on the gates to release the locks. These are the only gates in the Brazos River Authority that are not controlled remotely.

brazos_dam
"These nine crest "roof weir" type gates are each about 74 feet [22.6m] long and 13 feet [4m] high. Depending on the streamflow and lake elevation, each gate can pass up to 9,600 cubic feet per second of water when open."

There is also an uncontrolled emergency spillway on the south side of the dam. So far, it has not been used.

Satellite

5:53 video @ 0:32 (source)

@ 3:31
Brazos River Authority Gate Operations
The three low-flow gates can release 100-150cfs per gate. The 78" and 42" conduit ring jet valves can release 3,000cfs. This source specifies 9,000cfs for each bear trap gate.
[This video erroneously attributes the invention of radial gates to Tainter in 1888 instead of to Patrick Thibado in 1880. [Dennis DeBruler]]

@ 4:03