Miles Glacier

Miles Glacier was a station located at milepost 49 of the Copper River & Northwestern, and is the south/west end of the Miles Glacier Bridge – the largest and most expensive of the steel bridges on the CR&NW.  It was also the site of a construction camp during the building of the railroad, a two-story wooden station / maintenance building at the southeast corner of the main spans, and a large curved wooden pile trestle approach (including a wye) on the north side.

Million Dollar Bridge

The Miles Glacier Bridge – consisting of four large steel Pennsylvania Truss spans – is frequently referred to as the “Million Dollar Bridge” in reference to its $1,424,775 cost at the time of construction in 1909-1910.   Erastus Corning Hawkins, the CR&NW’s chief engineer, is responsible for the bridge’s overall design, with the trusses fabricated by the American Bridge Company.

The bridge carries the railroad over the Copper River for its second time after leaving Cordova, crossing from the east bank back to the west bank.  The alignment takes advantage of a narrow channel to allow the railway to avoid two active glaciers – Childs Glacier downstream on the west bank, and Miles Glacier upstream on the east bank.

Construction started in May of 1909 under the guidance of bridge engineer Albert Clay (A.C.) O’Neill (sometimes spelled O’Neel).  The final span – span 4 – was completed in June 1910.  The truss spans were built on timber falsework driven through the winter ice, and the final span was made self-supporting just hours before the spring break-up.  The spans are numbered 1-4 from the Cordova end, and are 403′ 11″, 304′ 5″, 441′ 5″, and 416′ 8″ in length respectively.  The bottom chord of the trusses is approximately 175′ above sea level, while the water of the rushing Copper River can fluctuate from 135′ to 155′ underneath.

The glaciers were ever a threat to the bridge.  Miles Glacier continuously calves from its face, creating not only enormous waves as the ice crashes into the river but also massive icebergs floating down the river.  As a result,  the bridge sports unique steel-tipped concrete icebreakers ahead of the piers.  At points in history, there is evidence that the two glaciers have actually closed the gap between them.  An 1885 US Army survey expedition found that Childs Glacier was only approximately 360 feet from the site of the bridge.  When construction started in 1909, there was a decent sized gap between the glaciers (reported at three miles), but both started advancing rapidly in 1910.  Childs Glacier, downstream, began advancing up to eight feet per day and got to within 1475 feet of the bridge in June 1911, but that was as close a call as has ever happened.  Since then, both glacier faces have retreated and have come nowhere close to the structure.

During the construction of the bridge, the railway ferried supplies across the river using the steam ferryboat Gulkana, and during the winter rails were just laid over the ice.  This allowed construction to continue up the river while waiting on the large bridge to be completed.

In 1958, twenty years after the railway was abandoned, the bridge was converted to road use in an effort to build a highway on the old rail bed linking Cordova with the outside world.  On March 27, 1964, the Good Friday Earthquake struck, tilting and shattering the third pier and as a result, dropping the south end of span 4 into the water.  A ramp was installed between the end of span 3 and above the water line on the deck of span 4 in 1973, and a false bent installed to help support span 3 (should pier 3 fail completely) in 1975.

The false bent itself was destroyed and pier 3 were further damaged by flooding in 1995, forcing a decision on what to do with the bridge.  Without some action, the bridge would inevitably fail and block the Copper River, damaging a prime salmon spawning route and necessitating an expensive removal.  In 2004, work began to stabilize and repair the bridge.  Engineering work was done by TY Lin and the actual construction by Mowat Construction. Span 4 was jacked up on a temporary support, its damaged members cut away and replaced by modern elements fabricated to original drawings.  Pier 3 was demolished completely and a new pier 3 cast in its place.  By 2005, reconstruction work was complete and the bridge once again looks as it did when trains passed over it.

Photos

 

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