1899 Layton Bridge over Youghiogheny River and Tunnel Replacement near Perryopolis, PA

Historic Bridge: (broken Archived Bridge Hunter; broken Bridge Hunter; Historic Bridges; Satellite)

Tunnel: (Satellite)

New Bridge: (Satellite, planned)

The bridge is pin connected.

HistoricBridges
It was built by a railroad and abandoned in 1931. It opened has a single lane road bridge in 1933

In the background, we are looking through the tunnel.

Street View, Oct 2024

The ends of the tunnels are brick lined, but most of it appears to be bare rock.

Street View, Oct 2024

The pattern left by drill and blasting is interesting.

Street View, Oct 2024

I find it amusing that they are building a "river structure" instead of a bridge. What is so offensive about "bridge" that someone felt a need to invent a euphemism? 

Bill Ball posted

PSA: They broke ground last week and phase 1 starts next Monday [Jan 19, 2026]. It's gonna get pretty busy the next few years if you fish down this way.

https://share.google/AOOhXi2aacnRiGLLy

Jimmy Laux: I hope they leave the tunnel and old bridge add it to the bike trail somehow.

Bill Ball: Jimmy Laux it's going to filled with foam and sealed at both ends.

A shuttle service will be provided to bypass the 1.2 miles of the closed Great Allegheny Passage Trail.

pa, p6

Once again, a demonstration that listing a structure on a historic register just increases the red tape that needs to be processed. It doesn't preserve the artifact.

pa, p13

MonValleyIndependent

pa_projects
"Once the new bridge and roadway are complete, the old Layton Bridge will be removed and the tunnel will be closed."
[Why not make it a branch off the GAP Trail? The rock in the tunnel looked very competent, and I don't think the Coast Guard cares. I found no evidence that there is any barge traffic this far upriver.]

Vasas Media added seven photos with the comment: "With the construction of the new bridge starting soon, I’ve been wanting to make my way back out to Layton to photograph the old bridge and tunnel before they’re gone. Thankfully the weather was beautiful Friday morning and allowed me to capture it at sunrise. Completed in 1899, and converted for car use in ‘33, this bridge has carried countless people back and forth across the Youghiogheny. I’ve heard it even made an appearance in a movie or two. I wonder if the new bridge will also last 127 years."

https://www.pa.gov/agencies/penndot/projects-near-you/district-12-projects/layton-bridge

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1926-64+1965 US-101 Bridges over Klamath River at Klamath, CA

1926: (Archived Bridge Hunter; Bridge Hunter; no Historic Bridges; Satellite)

1965: (Archived Bridge Hunter; Bridge Hunter; no Historic Bridges; Satellite)

Joel Windmiller posted
Klamath, California, Douglas Memorial Bridge over the Klamath River, taken during the flood of 1955. The bridge was washed away in 1964. Christmas storms arrived. DOH Photo DN LRN 1 / US 101 / Redwood Highway

BridgeHunter_1926 attributes Joel's photo to HAER. But this is the photo I found there.

LC-DIG-pcrd-1d00523

2011 photo by Brian Smith at south side abutment via BridgeHunter_

BridgeHunter_1926

The replacement bridge also has bears at the portal.

Street View, Jul 2025

This view is good enough to guess that the replacement bridge is a steel-girder bridge. I presume that the slanted piers are an artifact of street view rather than reality.

Street View, Jul 2025

I did find a view with vertical piers.

Street View, Apr 2021

This is the original road alignment.

1952/54 Klamath Quad @ 62,500

This shows the new and old alignments of US-101. It also shows that the town of Klamath got wiped out by the flood as explained in the above plaque image. A satellite map shows that they rebuilt the town on higher ground.

1966 Requa and Fern Canyon Quads @ 24,000

Original Erie Canal Schoharie Crossing: Dam, Lock#19 and Guard Lock at Fort Hunter, NY

Dam: (Satellite, approximate)

Lock #19: (Satellite)

Guard Lock: (Satellite)

Erie Canal Overview

The Original Erie Canal cross Schoharie Creek by using a dam to create a pool that raised the river to the canal's level.

ErieCanal

This map shows the paths of the Original (red), Enlarged (yellow) and Barge (green) Canals. The dam would have been downstream of the red line. The Enlarged Erie Canal used an aqueduct to cross the creek. When the Enlarged Canal opened in 1841, the Original Canal west of the creek was abandoned. But the dam and the Original Canal to the east was retained as a feeder canal for the Enlarged Canal. That is why we now see remnants of the Original Canal on the east side but nothing on the west side.

Google Earth, Sep 2020 plus Paint

Bob Baxter, Jul 2021

Joel Torres posted two photos with the comment:

"The East Guard Lock" at Schoharie Crossing in Fort Hunter, N.Y.

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This view confirms that I found the correct location for the guard lock.

Street View, Jul 2019

1953 39mw Tenkiller Dam and OK-100 Bridge over Illinois River near Gore, OK

Dam: (Satellite)

Bridge: (Satellite)

Aux Spillway: (Satellite)

Main Spillway: (Satellite)

Inlet Control Works: (Satellite)

Outlet Works: (Satellite)

Powerhouse: (Satellite)

TownOfGore

USACE_lake

WildlifeDepartment
"Impounded in 1952, Tenkiller is the only controlled impoundment on the Illinois River and can experience prolonged drastic lake level fluctuations....Due to its depth, the lake provides cool water for the popular year-round trout fishery in the tailwaters."
[I did see a lot of photos of people fishing downstream. And there must be bass in the lake. (I didn't watch it.)]

dvidshub
"Photo By Brannen Parrish [USACE provided] | The State Highway 100 Bridge over Tenkiller Dam's main spillway, near Gore, Okla., awaits motorists in the late afternoon sun, Sept. 9, 2025. The U.S. Army Corps of Engineers, Tulsa District will close the bridge for demolition and replacement starting Oct. 6, 2025. The bridge has served motorists enabling passage over the spillway for more than seven decades."
Demolition and construction is expected to take 2.5 years and cost $28.7m.

The old bridge was a steel girder bridge. I don't know if the new one will be steel or concrete.

USACE_project

I was not able to find an overview photo on any of the USACE web pages, but I did find this drone video. The main spillway is in the center and the aux spillway is on the right. The earth dam is to the left of the aux spillway in the background because the road does a 90-degree bend after the aux spillway.

2:32 video @ 0:08

It looks like the spillway flow is carving off huge blocks of rock. I wonder what type of rock it is.

@ 1:25

But I still don't have an overview of the earth dam, so I'll go with a satellite image. From left to right: powerhouse, outlet works, inlet works, main spillway, aux spillway and earth dam.

Satellite

I had to dig deep, but I finally found that the powerhouse has 2 units for a combined capacity of 39mw. I still don't know the flow rate when the generators are operating. [HydroReform]

Why won't USACE include these numbers on their webpages?

I wish all USACE websites had a graphic like this.

USACE_tenk

GreatFallsTribune
[They have not updated this data to include the aux spillway.]

Spillway and Outlet Works:  The main spillway capacity is 290,400 cubic feet per second (cfs) at maximum pool (elevation 672.2) with flow controlled by ten 50- by 25-foot tainter gates. The auxiliary spillway capacity is 229,340 cfs at maximum pool with flow controlled by five 50- by 35-foot tainter gates. The crest of the main spillway is at elev. 642 and the auxiliary crest is located at elev. 632. A flood control outlet extending through the narrow ridge comprising the right abutment consists of a 19-foot conduit.  Capacity of the conduit is 23,300 cfs at the top of the flood control pool.  Flow through the conduit is controlled by two 9- by 19-foot tractor-type service gates installed at the upstream end of the conduit and operated by individual electric hoists located on the operating floor of the gate tower structure.

Hydrologic Data: Estimated peak discharge and volume of the December 2015 flood were 149,200 cfs and 900,763 acre-feet, respectively. The record peak release was for this flood at 35,000 cfs.  Total runoff from the drainage area above the site was 10.48 inches for the entire period.  The March and April 1945 flood had more total runoff with lower peak flows at 1,184,000 acre-feet and 118,000 cfs, respectively.  Total runoff from the drainage area above the site was 13.79 inches for the entire period.  The May 1950 flood had a peak discharge of 180,000 cfs with a volume of 720,000 acre-feet, which is equal to 8.39 inches of runoff. 

[USACE_data]

Just 35kcfs makes a big splash.

USACE, Tulsa District posted
"Here's a look above and below Tenkiller Dam at about 3:00 p.m. today [Dec 29, 2015] as they were releasing just under 35,000 cfs after receiving several days of heavy rain throughout the region."

All of the photos I found were of the bridge over the main spillway. Here is a view of the bridge over the aux spillway. No one talks about replacing this bridge. When was the aux spillway built?

Found the construction date: "Construction of the auxiliary spillway was completed in January 2009." [USACE_data]

Street View, Apr 2025

Jan 2026:

David Holeman posted four photos with the comment: "Went by tenkiller dam and took a few more pictures of progress. They got the bridge deck off of it."

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1961,1979 2.6gw Chief Joseph Dam and Rufus Woods Lake on Columbia River at Bridgeport, WA

(Satellite)

Street View, May 2023

Columbia Basin Research, Image Source: USACE Digital Visual Library. Image File Number: 4900-19. Photographer: Unknown. Date: 1/1/81.
Units 1-16 were constructed in 1961 with a nameplate capacity of 64mw and an overload capacity of 88.3mw.
Units 17-27 were added in 1979 with a nameplate capacity of 95mw and an overload capacity of 109.3mw.
The hydraulic capacity is 219kcfs.
The spillway is 980' (299m) long with 19 gates.

USACE
"Chief Joseph Dam is the second largest hydropower producing dam in the United States."

USACE_hydropower
"Chief Joseph Dam is a 'run of the river' dam which means the lake behind the dam is not able to store large amounts of water. Water coming to Chief Joseph Dam from Grand Coulee Dam must be passed on to Wells Dam at approximately the same rate. With 27 main generators in the powerhouse, it has the hydraulic capacity of 213,000 cubic feet per second (cfs), or 1,593,000 gallons per second.    In the event more water was passed on to Chief Joseph Dam than could be used for power generation, the spillway gates would be opened to pass the excess water. With an average annual flow rate of 108,000 cfs, the Columbia River seldom exceeds the powerplant's capability to pass water. Spilling of water is infrequent at Chief Joseph Dam."

USACE, Seattle District posted

“What the heck am I looking at here?” A lot of hydropower is what. 

It doesn’t look like much to the untrained eye, but this is a "busy" photo of Chief Joseph Dam’s powerhouse. 

Extensive capital improvement work is currently underway at Chief Joseph, near Bridgeport, Wash. on the Columba River.

Seattle District operates and manages USACE’s largest hydropower project and the Nation’s second largest hydropower producing dam. (We like to gloat.)

Zoom in a little and you can see two upper brackets stacked on top of Units 3 & 4, while our General Electric contractors simultaneously work the generator rewind project on Units 7 & 10. 

Also, there's a tiny human for scale near the bottom left, because these units are massive!

Just another day to ensure clean, reliable hydropower makes it to the power grid.

They had to dig a huge power canal on the side of the river in order to get a powerhouse that was long enough to handle the flow of the river. So the spillway is effectively a huge diversion dam.

SpokaneHistorical

Thomas O'Keefe Flickr via hydroreform
hydroreform specifies a capacity of 2.5gw and an annual net output of 11,239gwh.

And this specifies a capacity of 2.6mw. They must be upgrading the units.

USACE, Seattle District 0:25 video

Chief Joseph Dam is the nation’s second leading producer of hydropower, capable of producing over 2,600 megawatts (MW) of electricity – enough to power the Seattle metro area.

Its discharge outflow on the day of this video was approximately 250,000 cubic feet per second (cfs) or 12 MILLION gallons per minute. That’s enough to fill about 170 Olympic sized pools in a minute!

[Or one pool in 2.8 seconds.]

The dam does not have a fish ladder, and the blockage of fish is an issue.