1886+1979 (NS/Sou)+(CSX/L&N) Bridges over Tennessee River at Decatur, AL

(Bridge Hunter, Satellite)

Not only do NS and CSX share this bridge, the satellite image shows that they fork in the river on the north side.

1885 Swing Bridge

Street View, 1978-79 Lift Bridge
[The clearance is just 30' so it needs to be raised for barge traffic.]

Street View, maximum resolution

History of Decatur Alabama posted two images with the comment:

Old swing span on Decatur,AL railroad bridge

As you may remember from prior postings, the vital railroad bridge in Decatur was first a wooden bridge built in 1855.  This bridge was burned in 1862 at the time the Union Army was first occupying Decatur and was temporarily replaced by a pontoon bridge for human and wagon usage.

 By 1866 the bridge was replaced with an iron and steel structure, much of which was built on the original pilings.  This bridge was a "swing bridge" in design meaning that it opened for river traffic by swiveling on a piling built in the middle of the swing span.  The river was narrower in those days but the giant TVA dams both raised the depth level and the width of the river and its adjacent lakes.  This also somewhat moved the navigation channel for boat traffic.

The swing span became functionally near obsolete by the mid-1930s as it was located too close to the south bank of the river (whereas the channel had moved closer to the middle of the present day river/lakes).  It also failed to line up with the lift spans of the Keller Bridge and the swing type design required an extra piling in the middle of the channel upon which the swing mechanism rested, thereby cutting the width of the navigation channel in this area by 50%.   All of this made boat navigation hazardous and dangerous as well as extremely time-consuming for boat pilots.  Barges had to be taken through the span virtually one or two at a time while many of today's tows consist of  15 barges-- 3 wide and 5 deep pushed by one tugboat.  Barges hitting the railroad-- and automobile bridge(s)-- were a common and dangerous occurrence .What was a 10-15 minute process for pilots today often took hours in the past-- and longer if the river's current and waves were not cooperative.

The solution occurred in 1978-79 when the graceful but outdated swing mechanism was replaced by a lift span.  This span was located much closer to the center of the river's channel today, was lined up with the lift span openings for the old Keller Bridge and the now permanent openings of the Hudson bridges, and eliminated the need for a piling under the span, thereby enormously widening the boat channel available to tugboat captains.  Today, 15 barges at one time can easily and quickly (for experienced pilots) pass under the raised lift within just a few minutes-- with a lot less hazard.

Louisville & Nashville Railroad Historical Society shared

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Dale Proctor posted
Southbound on the Tennessee River bridge at Decatur Ala., June 1983. This was after the lift span was installed and before the old swing span was removed.

Rick Smith: I hadn't realized that the swing span (which I used to ride across during the '60s and '70s) hadn't been removed by the date shown,1983.

The lift-span was completed around 1979, and I assumed it was operable by then. Just wondering.

Michael Clark: Rick Smith It was quite a while before they removed it. I think they were hoping to sell it to another railroad, and leaving it in place was probably cheaper than storing it somewhere.

Rick Smith: Thanks, Michael Clark.

Any road considering buying that thing ─ or any swing-span for that matter ─ would have to have been pretty hard-up, since swing-spans are structurally dimensioned for a specific space between fixed-span ends. Plus, tension-compression members for swing-spans usually are not engineered to serve as fixed spans supported only at the ends and would require significant (and expensive) truss modification. Also, the cost of transport could significantly offset any advantage of its re-use, particularly for a Class-III road.

While I'm aware of several instances of moveable-span relocation, those cases have been either with Scherzer Rolling-Lift spans or with vertical-lift spans (along with their towers), since swing-spans are just outright navigational hazards and (woefully) afford the least channel clearance for today's commercial river traffic practice. I guess at the time hoping to sell the thing was a speculation by Southern, which built the vertical-lift replacement. CSX simply is a bridge tenant of that shared segment.

Two photos of the swing bridge proved by Michael Clark in the comments on Dale's post.

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My mother with her parents in a small boat on the bank of the river in front of the Decatur bridge circa 1941.

Brad McClelland posted
In the 1980's Seaboard System and early CSX used GE B30-7's on there intermodal trains. These locomotives were given a nickname of TOTE Boats, a L&N term for Trailer on Train Express.
On Friday October 14, 1988 at 2:40 pm, southbound R-121 crossing the Tennessee River in Decatur, Alabama. This former L&N main crossed Southern's Chattanooga to Memphis line. here at River Junction.

Ed Robertson posted four photos and a video with the comment: "Norfolk Southern vertical lift bridge crossing the Tennessee River in Decatur, Alabama. No luck spotting a train crossing but was able to get the bridge lift in operation."
David Mitchell Forrest Sharpe I remember when this was a swing span bridge and watched its conversion to a lift bridge. Between CSX,NS and the river traffic, it gets a good workout round the clock

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Some photos and a video

Jonathan Shoemaker commented on a post

 

SpeedShot Train Photography posted
BNSF 785 Leads a 3 unit Intermodal across the Tennessee River Westbound (South) on a stormy and sunny mixture of weather in Alabama.
[I wonder where that train did a run through.]

The first view I've seen from the north side. Looking at a satellite image, this is just a third of the river's width. The rest of the way north it is an embankment.

SpeedShot Train Photography posted
BNSF Leading a four unit mixed freight train Northbound, over the TN River in Decatur Alabama / September 2022
Roger Riblett shared

Brian Caswell Train Photography posted
CSX Loaded Coal across the TN River in Decatur Alabama - Southbound / 2022
Roger Riblett shared

2 photos posted by Matthew White.

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Jonathan Shoemaker posted five photos and a video.