Barrow of Boulders Appeal
Final Appeal Summary
The Barrow of Boulders Appeal was launched officially in October 2009 to raise money for materials for channel restoration between bridges 83 and 84. It had raised £43,345 by the time it was closed in early 2012. By the time that the channel lining was completed at the end of 2013, we had spent:
The excess was met from the Society's general fund.
Lembit Opik MP, John Bridgeman, British Waterways vice-chairman and Anna Turner, High Sheriff of Shropshire
launch the Society's Barrow of Boulders appeal at Redwith.
The aim of the Barrow of Boulders Appeal was to raise the funds to purchase the concrete blocks and stone required to line the channel between Bridges 83 and 84. The original design for channel lining used a clay liner consisting of a layer of bentonite clay sandwiched between two layers of woven plastic material. This liner is self-healing when punctured, as the bentonite clay can expand up to 16 times its normal volume when placed in water. To stop this occurring when the canal is re-watered, the liner requires an overburden to hold this expansion back until a hole appears. Our solution was to use concrete blocks stood upright to provide sufficient weight to prevent the liner from expanding and to hold the liner in place against the turbulence in the water created by boat propellers. To prevent the concrete blocks from damaging the liner, a geotextile (felt-like material) was placed between the liner and the concrete blocks. This system required approximately 90,000 concrete blocks to cover the 420 m of channel between Redwith and Pryces Bridges. The stone is used to finish the offside bank, either side of the waterline.
Original Lining Method – With Upright Concrete Blocks
The appeal has been incredibly successful and has raised a staggering £43,345 since it was launched in 2009. As the concrete blocks used to date have been funded through other sources, the Society believes that the total raised so far has reached a point that will pay for the remainder of the concrete blocks and stone required for the current length being restored. This is a tremendous result and the Society wishes to thank all those who have donated towards the Appeal and those that have given up their time to make the appeal so successful.
However, the good news doesn’t end there...
We are now using a new lining material in place of the bentonite liner, which was heavy and difficult to handle. It utilises the same geotextile used as protection previously, but it is factory treated with a new waterproofing acrylic. When in contact with water, the acrylic swells and forms a stable gel that is self-healing when punctured. The demonstration involving a column of water supported by this treated material, punctured by a pen knife, with no water leak through the material even when pulling out the knife, is very impressive and convincing. As there is no swelling to hold back, the liner can be used without overburden, but overburden is required to prevent the liner being affected by future dredging. Calculations show that the concrete blocks can now be laid on their side instead of needing to be upright.
New Lining Method – Much Simpler, Quicker to Lay and Cheaper Overall
So, the new liner has many advantages:
- The existing bentonite liner is no longer required, saving considerable time and effort as it was difficult to handle and took time to lay. The remaining rolls of liner that were provided by British Waterways will now be utilised to reduce the cost of the planned expansion of the Aston Nature Reserves
- As the blocks can be laid down, we now only require approximately 40,000 concrete blocks for the 420 m length between Redwith and Pryces Bridges. A considerable saving in cost, environmental impact and manual labour, something that the restoration volunteers are very pleased about! The first weekend of March 2012 we laid 18 m in one day, less than half the time using the old system!
- As the new lining system is easier, and therefore quicker to lay, we will require less hire of equipment which will offset the small additional cost for the acrylic treatment of the geotextile.
By moving to this new liner system, the money raised by the Barrow of Boulders Appeal is thought to be more than that required to finish lining the current length. The Society has decided to hold the remaining amount in a Restricted Fund, to be used for channel lining material on future restoration work undertaken. The Appeal is therefore closed, although any further money donated from forms already distributed will continue to be added to the total in the Restricted Fund.
The new liner has effectively more than doubled the value of all the donations to the Barrow of Boulders Appeal. Good news for the continuing restoration of the Montgomery Canal.
The first major delivery of 4,000 blocks for channel lining arriving at Redwith