Cornwall Heritage Trust has launched an appeal to save the magnificent Treffry Viaduct towering so majestically over the beautiful Luxulyan Valley Country Park. Not only is it a very beautiful landmark, but those who are familiar with this wonderful imposing feat of Cornish engineering will understand why it is so important to save a quintessential part of our great industrial heritage. The work needed to save the viaduct is estimated to be in excess of £2m and so we are urgently appealing for donations to our Treffry Viaduct Repair Fund.
A large part of the magical appeal of the Luxulyan Valley has always been the water running in the leat system, once used to power the tramway and machinery on the Fowey Consols copper mine. Nowadays the water still serves a useful purpose, and is sent in a pipeline down the hillside to a hydro-electric generator at Ponts Mill. The magnificent ten-arched Treffry Viaduct, opened in 1842 and now owned by Cornwall Heritage Trust, forms the centrepiece of the leat system. However, a recent survey revealed a new and very large leak from the base of the viaduct posing a serious risk to the footings of the masonry.
Other water leaks have caused significant erosion of mortar from the masonry joints as well as encouraging vegetation to take root, causing still further damage to the joints and mortar. If we do not act quickly, the footings will be destroyed, ultimately leading to the collapse of the viaduct.
The viaduct is a masterpiece of 19th century Cornish engineering, having been built to carry both a horse-drawn tramway across the valley and also water in an aqueduct channel constructed below the tramway deck. However, for many years now, the viaduct has leaked water from the aqueduct channel. During the Trust’s ownership these leaks have constantly been repaired using traditional materials, which is both difficult and costly. Repairs involve lifting the heavy granite sleepers, which originally supported the tramway rails, above the area of the leak.
The base of the aqueduct channel is formed of granite lintels supported only by a layer of packed infill material. Over the 170 years since the structure was built, the lintels have gradually settled and sunk, often in an uneven fashion. This movement has opened up the horizontal joint between the bedstones and the sides of the channel, allowing water to escape outwards and downwards through the supporting masonry. The decision was therefore taken to shut off the flow of water completely in June 2013 and the Viaduct and the Carmears Leat have been dry since then.
Built between 1839 and 1842 by Joseph Treffry, the viaduct is 90 feet high and 670 feet long. The high-level crossing of the river was an advanced engineering project even by today’s standards and not only enabled copper and tin to be transported more easily to the south coast but also powered a water wheel to pull the heavy loads up the tramway. Although the tramway is now disused, the iconic and inspirational view of the viaduct across the Luxulyan Valley is a reminder of an iconic part of our Cornish industrial heritage.
Please help us to restore Treffry Viaduct and protect this wonderful landmark for the benefit of future generations.
Thank you !