Repairs to the Llangollen arm of the Shropshire Union Canal

The Llangollen arm navigable feeder to the Shropshire Union Canal between the River Dee at Llantisilio and Trevor Basin at Pontcysyllte Aqueduct has presented a series of major maintenance problems from its construction in 1805 until the present day. As this section of the canal is part of the recently designated Pontcysyllte Aqueduct and Canal World Heritage Site, there is particular interest in its civil engineering history. There have been 20 significant leaks and breaches of the arm since its construction and these are summarised and the more important ones discussed in this paper. There have been some rather innovative attempts at solving problems, notably those involving recurrent water loss. These have included stonewalling, concrete lining, corrugated iron sheets, interlocking steel sheets and asphalt lining with later repairs, as well as the usual clay puddling procedures. Many of the difficulties arose because of the nature of the route taken by the feeder canal on a geotechnically challenging hillside and very close to a rail line, a major road and the River Dee.