It is a well known fact that aggregate blocks manufactured by Forterra Building Products are versatile enough for virtually any construction requirements, but using them to line a derelict canal that closed because of leakage is a first in the company’s history! This highly unusual request came from the Wendover Arm Trust, a volunteer organisation dedicated to restoring the Wendover Arm Canal from Little Tring in Hertfordshire to Wendover in Buckinghamshire.
Phase One of the restoration was completed and opened in 2005 and work on Phase Two began on a mile length of dry canal between Drayton Beauchamp and Little Tring. The task involved profiling the canal to its original shape and lining the sloping sides with Forterra Evalast aggregate blocks on top of Bentomat lining as waterproofing.
Restoration Director, Roger Leishman has spent a lifetime in civil engineering and recognised the value of the Forterra Evalast blocks that are the perfect solution. “We are using Bentonite granules between two layers of artificial fibre; the granules expand when wet to form an impenetrable barrier,” he explains. “However, to control the expansion the Bentomat lining needs to be weighted down. As the slides are sloping and therefore, using spoil that would just slide off was not an option, we decided to try out aggregate blocks on a 60m section of the canal and it has been extremely successful."
“Initially, we used the hollow blocks but these will have to be infilled with concrete to provide the necessary impact resistance against boat hulls,” he continues. “This project is expected to take up to ten years to complete but when finished, there will be a row of infilled Evalast 215mm hollow blocks to provide a solid base over the Bentonite lining, and then rows of solid Evalast 100mm blocks on top.”
Another major advantage of the Forterra product is its light weight. “Bearing in mind that the workforce consists entirely of volunteers, the Forterra 100mm aggregate blocks laid flat make it much easier for handling and placing, being so much lighter than comparable blocks, and this is expected to speed up the restoration process,” concludes Mr Leishman.