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23/07/2021

Divers in Offaly discover possible 19th Century submerged bridge

Divers in Offaly discover possible 19th Century submerged bridge

Aerial view of the location of the wooden bridge which once spanned the Grand Canal.

Divers from a local sub aqua club have discovered a large wooden structure on the bed of the River Shannon near Shannon Harbour.
  This discovery has caused some excitement among local historians who think it might be the remains of a former Grand Canal bridge.
"The location of the find and the size of its parts," said local historian James Scully, "suggests that it could be the remains of what was a large wooden bridge spanning the Shannon at this location between 1828 and 1849."
An acoustic image of the feature was taken by a local history enthusiast and the image indicates a length of just over sixty feet, a width of sixteen feet with several large timber beams about eight inches in diameter.
“While it is too early to be conclusive as to the nature of the find,” said James, “should it transpire to be a component of this early nineteenth century bridge then it is of great historical significance.”
James and Kieran Keenaghan have amassed a bit of information about the bridge which they passed on to the Tribune.
James said the history of the bridge is well documented.
The Grand Canal was constructed from Dublin to Shannon Harbour over a period of forty-eight years between 1756 and 1804.
Twenty years later an extension to Ballinasloe was begun and was completed after just four years in 1828. This canal was fourteen miles long with just two locks. One, Fanning Lock, named after Nicholas Fanning, then chairman of the Grand Canal Company and located just upstream from the junction with the Shannon, and the other Kylemore Lock, near Laurencetown, halfway to Ballinasloe.
“The function of the bridge,” continued James, “was to enable horses to continue pulling boats from the terminus of the canal’s main line below Shannon Harbour, over the River Shannon to the towpath on the County Galway bank, and from there continuing on via Clonfert, Kylemore and Lismany to Ballinasloe. The bridge, which cost £2,769, had a swivel mechanism on the east or Offaly side. This enabled the deck to pivot horizontally thereby creating a clearway for the passage of boats.”
Unfortunately, from the outset the bridge malfunctioned. In fact six months before its official opening a steamboat collided with it causing thirty or forty shillings worth of damage. The sum of money was small, but it was the delay and the annoyance which caused the most upset to the steamboat companies.
Over the following years the bridge was reported as being “extremely objectionable as regards the river trade….”
“In spite of frequent repairs,” continued James, “the timber fabric decayed often resulting in injuries to the towing contractors’ horses.”
Initially the problem seems to have been with the swivel mechanism on the east side but this was exacerbated by the incompetence of the bridge keeper. In addition the great expansion in the size of steam-powered vessels militated against plain sailing. The Lady Landsdowne, built in 1833, was typical of the new steam propelled vessels then using the Shannon navigation. She was one hundred and thirty-five foot long and seventeen feet wide while the horse drawn barges on the canal were just sixty feet long and thirteen feet wide.
In an effort to stem the tide of incidents and hold-ups, a bascule bridge with two sections which could be raised and lowered using a system of counterweights, was inserted in the centre of the bridge in 1840. This bridge was built by William Burgess of Limerick to the specifications of a design by Thomas Rhodes, principal engineer with the Shannon Commissioners.
Unfortunately this did not solve the problem and the proposed clearway of forty-five feet was much constricted leading to great dissatisfaction among the captains of the steamboats who sought to adhere to advertised sailing schedules.
“In June 1842, Henry Renton,” commented James, “resident engineer with the Shannon Commissioners for the new bridge at Banagher then under construction, was instructed to estimate the costs of removing the failed bridge.
“Over the following years matters did not improve. In February 1849 it was reported that the bridge had fallen down. Later that year it was replaced by a ferry boat which, using a winch apparatus, carried the horses on board across the river while also towing the boats behind. This ferry remained in operation for about seventy years until the canal boats themselves became mechanized and were able to travel under their own steam.
Whatever the outcome of this discovery may be there is no doubting the remains of the ferry boat with its winching mechanism still sits largely intact in mud and shallow waters close to the site of the wooden bridge. This boat is about forty-five feet long with almost all of its metal components surviving.
“While the existing wooden parts of the vessel would be prone to decomposition if it were raised, it would be a worthwhile project to rebuild the vessel using the original structure as a model. Meanwhile should the large structure discovered at the bottom of the Shannon turn out to be part of the wooden bridge then it would be worthwhile extracting them and displaying them for visitors, therefore making another welcome heritage attraction in the unique canal village of Shannon Harbour.”
Donal Boland is living on his barge in the vicinity of the wooden structure. Donal told the Tribune that he has been living on a barge on the River Shannon for the last 20 years. Donal is a marine archaeologist by trade and he was testing a new piece of sounding equipment called a Sidescan Sonar when he detected an anomaly in the river.
He contacted the sub aqua club in Banagher and they dived down to examine the anomaly. “They said the structure was many feet in length and was made of wooden beams which were eight inches in diameter. It was certainly no boat. I think it's pretty certain that it's the wooden bridge from the 1840s. It's unlikely to be anything else.” Donal said sub aqua divers attached to a governmental department might examine the structure during the summer and try to figure out what it is.

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