1925,1987 5mw O’Shaughnessy Dam and Birdge on Scioto River upstream from Columbus, OH

(Satellite)

The dam was built in 1925 as a water supply dam. [kiddle]

DelawareOhioHistory
The dam cost $1.54m and holds 6.3 billion gallons of water. 
"The project was of such a scope that a contractor was hired that had experience building metropolitan skyscrapers; the Thompson-Starrett Company was responsible for such structures as the General Motors Building in Detroit and the landmark Woolworth Building in New York City."

It is a fixed-crest dam (no gates on top). The current bridge doesn't appear to have any girders, just slabs.

Dave Neel-Surrena, Mar 2018

The dam is 1510' (460m) long with a spillway width of 802' (244m). The max discharge rate is 261kcfs. [NewarkAdvocate] 

261kcfs is a lot. I wonder how much the downstream river valley can handle without flooding. As the river flows to Columbus, there are some rather narrow spots in the river.

ColumbusLibrary, 1957 photo by Matthew Mosbacher Sr., no copyright
"Water spilling from the O'Shaughnessy Dam during the 1957 flood. The dam was completed June 1, 1925.  The reservoir, created by damming the Scioto River, provided a needed water source for the city. The reservoir is 912 acres in size and has 18.4 miles of shoreline. Maximum depth is over 40 feet near the dam, although much of the water is 20 feet or less."

DelawareOhioHistory, © JEFF HINCKLEY
A 5mw power plant was installed in 1987. It was abandoned in Feb 2017. $15.3m was approved in 2023 to refurbish the plant to produce electricity again.

The power plant can't be used all of the time because sometimes the flow in the river is too low. Since the main function of the dam is water supply, I expect they can run the plant only when water is going over the spillway. But of all the photos and videos I looked at, this was the only one that had a dry spillway. But photos are probably biased towards spilling water because they are more impressive. In general people will go out of their way to capture a big flow over the dam.

VisualOhio
This source puts the capacity of the spillway at 100kcfs. Although the author is careful to note that the information was provided by Google Bard AI.
[I presume that the Ferris wheel in the background is part of the Columbus Zoo and Aquarium. But I could not find that wheel using street view.]

The river downstream does appear to have good capacity because the rainstorm on Aug 21 flooded I-70 a little east of here.

usgs

Originally, the dam had a closed-spandrel arch bridge across the top.

W E Ayres postcard #123890 via Columbus Metro Library via Bridge Hunter

This was the post that motivated this research.

Facebook Reel

Victoria Vara: This dam doesn't have flood gates. It's just rolling over the normal crest.

1955 Lewisville Lake Dam on East (Elm) Fork Trinity River upstream of Dallas, TX

(Satellite)

USACE

The USACE completed this dam in 1955 to replace the Lake Dallas Dam. Construction of the Lake Dallas Dam began in 1928 as "the principal source of municipal water for its owner, the city of Dallas." It was 80' (24.4m) high and 11,000' (3.4km) long. This dam is 125' (38m) high and 33,000' (10km) long. "The huge lake that resulted was thirteen miles long, had a 183-mile shoreline and a capacity of 436,000 acre-feet at an elevation of 515 feet, and covered almost one-fifth of Denton County." [tshaonline]

This twdb source has different capacity figures than the above source has. Since the main functions of this dam are water supply and flood control, lake capacities are important.

twdb
The elevation at the top of dam is 560 feet above mean sea level, while the maximum designed water surface is at the elevation of 553 feet above mean sea level. At top of flood control pool (crest of emergency spillway), at an elevation of 532 feet above mean sea level, the lake covers 39,170 acres and stores 989,700 acre feet of water. At the top of the conservation pool, at an elevation of 522 feet above mean sea level, the lake covers 27,175 acres and stores 598,902 acre feet of water.

To add to the confusion, this source says the dam "holds back 2 million acre-feet, or 2.5 billion tons [0.6 trillion gallons], of water when the lake is full."  The normal definition of "full" is the conservation pool, 522'. They must be defining "full" as the maximum designed water surface, 553'. Note that 31' (9.4m) of water would be flowing over the spillway and the water would be within 7' (2.1m) from the top if the reservoir ever got this full.

Fort Worth District, U.S. Army Corps of Engineers posted five photos with the comment: "Construction of the Lewisville Lake dam was completed in August 1955. For more than 70 years the lake has been providing flood risk management for the Lewisville area and downstream communities along with supplying water to neighboring communities and recreational opportunities."

1

2

3

4

5

This is not the spillway. It is the outlet.

YouTube Short

This is the spillway. I had a hard time finding it because it is way off to the side. Probably so that the water will flow over more competent riverbank soil. In fact, looking at a satellite image, under a thin layer of soil is bedrock.

The spillway apron obviously needs repair work. I wonder how many times water has flowed over this spillway. (I looked through past Google Earth images. A few times, and the apron has been torn up and repaired before.)

Google Earth, Jun 2022 (Satellite)

The next Google Earth images shows that they had started much needed repair work on the spillway.

Google Earth, Jun 2023

The latest image available shows that they are still working on it.

Google Earth, Oct 2025

Dec 12, 2015

DallasNews
"Sandbags and tarps have been deployed in an attempt to prevent further erosion of a 160-foot-long slide on the Lewisville Dam. To engineers, the slide’s proximity to another major one that happened in 1995 suggests instability that could threaten the dam’s foundation."
The Dam Called Trouble
[Read the article, there were too many issues for me to summarize. Of note, there was a sand boil and piping during a rainstorm in an area that had leaked for years. Fortunately, the operations team was able to stop the piping by placing "a one-layer ring of sandbags around the sand boil, allowing the pool of water inside to rise about six inches. The method is supposed to equalize the pressure and prevent the water and soil particles from expanding."
Also of particular note, a breech "would submerge downtown Dallas in roughly 50 feet of water, the Corps estimates, causing more than $21 billion in property damage....“It would be a much bigger magnitude to the Dallas area than Hurricane Katrina was to New Orleans,” says Vazquez [The dam's operational manager]."]

$39.1m was awarded in 2019 to improve drain seepage areas. [news_2019] (I wonder what was used for the core for this dam. Or did they not bother to put a cutoff wall in the foundation. More drains sounds like a patch, not a fix.)

$76.1m was awarded in 2022 to repair the spillway. This time they will anchor the apron to the underlying bedrock using post-tensioned anchors. [news_2022]

RED ALERT: bogus AI. If they are going to use AI, I guess it is good that it is really bad so that you know it is AI. The "photo" itself is obviously bogus because many of the diagonal rods don't make sense. But when you compare the "photo" to the real spillway, it becomes absurd.

OceanCraft RC posted

At Lewisville Lake Dam in Texas, engineers are strengthening the spillway by drilling more than 70 high-capacity post-tensioned anchors through the concrete and deep into the underlying bedrock.

The anchors essentially lock the spillway to the rock below, increasing resistance against uplift and sliding when enormous water pressures act beneath the structure during floods.

Sinkhole closes I-44 and part of I-70 in St. Louis, MO

(Satellite)

If that hole had opened a little to the West, cars on Broadway might have fallen into it. If it opened up a little to the South, the pylon for I-44 would have been exposed.

reddit
Avoid I-44 in Downtown St. Louis. A huge sinkhole has opened up under the interstate bridge. This section will be closed until further notice.

KMOV posted
The St. Louis Metropolitan Police Department shares a map showing the routes that will be closed due to the sinkhole that formed on Broadway and Biddle.

If they had so much water leaking that it eroded a hole that big, why didn't the water department notice that the flow was way too high and dispatch someone with ground penetrating radar to find the hole while it was much smaller?

FirlstAlert4
"Multiple water main breaks caused a sinkhole to form near Highway I-70.(KMOV)"
"This caused a sewer washout, leading to the collapse of a 12″ and a 10″ main into the excavation site."
"Crews are working to address what is likely a failing valve. The water division said there is no timeline for when this will be repaired." [The tank that almost exploded in California because of a bad valve and this incident tells me that valves should be periodically tested.]
Water main breaks have become more frequent as the water district has accumulated $700m of deferred maintenance needs.

Facebook Reel

The hole is getting close to the pylon on the other side of the interstate.

Facebook Reel

A couple of days later the St. Louis water division says They're still working to figure out why the collapse happened. They are trying to dig down to the sewer, but it is 35' down. Fortunately, the sides of the hole are no longer sloughing off.

Facebook Reel

$84m Canyon Tunnel Collapse, Apr 14, 206, a Woman Worker Was Killed

Inlet: (Satellite)

Outlet: (Satellite)

The Canyon Tunnel is yet another water supply project in California.

The tunnel will be 12,000' (3.7km) long. The collapse was 200' (61m) into the tunnel. [modesto]

This scene is at the outlet.

2:14 video @ 1:08
3 impacted in Northern California tunnel collapse
One person is dead and another was taken to the hospital after a collapse at the Canyon Tunnel Project on Tuesday, the Modesto Fire Department said. A third person impacted by the collapse was unhurt.

The worker who was killed was 35-year-old engineering advisor Twyla Capurro. She is survived by two children.

The existing irrigation canal was cut into the side of steep Sierra foothills, and it is at risk for landslides and rockfalls falling into the canal and cutting off the water supply. The video contains scenes of workers removing rock from above the canal.

4:32 video @ 0:19
Canyon Tunnel Project | Introduction 2021 | Full Length

CanyonTunnelProject_FAQ
[This project website doesn't say boo about the collapse and the impact on the project.]

I've read before that the rock in California is "incompetent" because of all of the earthquakes. It seems that a risk of a tunnel collapse would be worse than the risk of a landslide in terms of the impact on the water flow. I hope they don't spend $84m in vain.

Falls, Dam, 2.6mw Power House, Mill and Bridges on North Branch Muskoka River in Bracebridge, ON

Falls: (Satellite)

Railroad Bridge: (Satellite)

Road Bridge: (Satellite)

Dam: (Satellite)

Power House: (Satellite, this is the intake control structure. This is the power house.)

Mill: (Satellite?)

It looks like they maintain their truss bridge.

Facebook Reel

Some docks and walkways are under water, but a good power wash should restore them.

Same Reel

John de Freitas, Jul 2024

LakelandGeneration

LakelandGeneration_history
"In 1894, the Town of Bracebridge established itself as the first municipality in Canada to own and operate a water-power electrical generating station." This was called Bird's Mill and produced 84kw.
"A second turbine was added that pumped water up a main street watermain."
In 1902, a 300kw unit was installed, and second 300kw unit was installed in 1905.

The 600kw station had a head of 10m (33'). "In 2012 the facility completed a series of upgrades, which have expanded the facility’s capacity to 2.6 MW.  Upgrades to the facility involved modifications to the existing powerhouse, turbine and generator replacement, installation of a new penstock, electrical system upgrades and deepening of both the intake and tailrace channels.With significant technology advances in the past century, the renovated facility now boasts one (1) Norcan S-Type Hydraulic Turbine as well as one (1) SAB Horizon Brushless Synchronous Generator, which are controlled by a Rockwell Automation ControlLogix system." [OntarioRiversAlliance]

nacsworld
The 2012 upgrade replaced all of the power generation equipment without damaging the existing buildings, "all while working in close proximity to a pristine water environment with stringent environmental protection measures and fish habitat protection." The flow was increased from 10m3 to 27m3 (353cfs to 953cfs).

NorcanHydro, cropped
"We supplied...a runner size of 83 in., 2108 mm."

NorcanHydro

NorcanHydro

Somewhere I saw that the upgrade cost $11m. but now I can't find that reference.

Ferdinand Lapuz, Sep 2023

Shradhdha M, Sep 2024

1906 28.5mw Minidoka Dam on Snake River for Irrigation

(Satellite)

Minidoka Dam is a storage and diversion dam for two different irrigation canals.

Satellite

These would be the gates for the Gravity Canal that is on the south side of the dam. In April, they are opening the gates to start the irrigation season.

Facebook Reel

Same Reel

Same Reel
Three pump houses pump the water up 30' (9m) for a total of 90' (27m).

Photo via uidaho, "Minidoka Dam and Reservoir near Rupert", Archival Idaho Photograph Collection, University of Idaho Library Digital Collections, Public Domain

nps
"Today, the multi-faceted Minidoka Project, which provides irrigation water to more than one million acres, counts a total of seven dams and thousands of miles of canals, laterals and drains. Still at the core is the more than 100-year-old Minidoka Dam, significant as the Bureau of Reclamation’s first embankment dam and the first Federally-built dam in the Pacific Northwest to include a powerplant to supply electricity. Minidoka Dam stands only 86 feet [26m] high, but its spillway, designed to handle the great flow of the Snake River, is made of concrete and stretches 2,300 feet [701m] long, or nearly one-half of a mile."
"Over the years, Minidoka Dam has undergone additions and repairs, including the current reconstruction of its spillway. A sixth generating unit was installed in the powerplant in 1927, and a seventh in 1942. Then, in the early 1990s, work began on a new powerplant, with Units 8 and 9 added in 1997. Reclamation retired the original five generators from service but preserved them as museum pieces in the original powerhouse building, where visitors still can see them."

Bureau of Reclamation posted four photos with the comment:

⚡ Hydropower: Meet the Bureau of Reclamation’s oldest.  

More than a century of hydropower history lives at Minidoka Dam in southern Idaho.  

The original Minidoka Powerhouse began generating electricity in 1909, making Minidoka the oldest operating hydropower facility operated by the Reclamation.  

Here’s this historic powerhouse by the numbers:  

⚡ 28 megawatts of generating capacity  

⚡ 4 generators across two powerhouses  

⚡ About 100 million kilowatt-hours of average annual generation  

⚡ Enough electricity to supply approximately 7,000 to 10,000 homes for a year

Minidoka Dam is 86 feet tall and stretches 4,475 feet — about 0.85 miles — across the Snake River.  

💡 Fun fact: Construction on Minidoka Dam began in October 1904. By April 1910, the nearby communities of Burley, Rupert and Heyburn were receiving both irrigation water and electricity from the Minidoka Project.  

More than a century later, Minidoka is still generating power.  

Dam impressive. Powerfully Reclamation. ⚡  

📸1: Water flows from the Minidoka Powerhouse into the Snake River near Rupert, Idaho. 

📸2: Minidoka Dam switchyard, Minidoka Irrigation District headworks, and the Minidoka Powerhouse along the Snake River near Rupert, Idaho. 

📸3: Generating units line the interior of the Minidoka Powerhouse near Rupert, Idaho. 

📸4: Minidoka Powerhouse operates along the Snake River near Rupert, Idaho.

Brett Wanamaker shared

usbr
"The combined generation capacity of all four units is 28.5 megawatts, with a combined flow of 8670 cubic feet per second."
In 2015, the new $21.3m spillway with radial gates replaced the original spillway that used stop logs.