Montgomery Canal Restoration Work Party Report - May 2010
May 1 - 3
The only three-day work party of the year saw a great deal of progress. The weather ranged from glorious warm sunshine, to cold winds and overcast skies. Numbers were slightly down on previous months, but all those who attended worked hard to make up for it. Work progressed in five main areas.
At Pryces Bridge great leaps forward were made in preparations for the concrete base. Where for the last year a waterlogged, mud-filled ground has been waiting to swallow up any volunteer who lets their boots sink too deep, there is now a stabilised base, with a cement blinding applied. In the trench which was previously dug across the canal bed under the bridge, sheet piling has been driven in by hand, providing a cut-off for water seepage. At each end of where the base will be, a downstand has been dug, to provide extra strength and again help prevent the base shearing. On top of the blinding, steel reinforcing bar has started to be laid. As with most of the engineering challenges we are facing, this is more complex than it first appears! The reinforcing will be in two horizontal layers, with a separating gap between them. In the downstands at the ends and in the centre, the reinforcing is shaped to bend down into the downstand, then back up again. At the sides, the reinforcing is bent into a U-shaped section, to tie the upper and lower layers together. Finally, at 300 mm intervals, holes are drilled into the bridge walls, and reinforcing is placed into the holes, and tied into the rest of the reinforcing, again to help prevent shear. Hopefully the placement of the reinforcing will be completed next month, and the concrete for the base can then be poured. The work at Pryces bridge started over a year ago, with the rebuilding of the bridge walls, and it will give a great sense of satisfaction to see this work completed.
A section of channel was shaped to the correct gradient near to Pryces Bridge. While previous channel shaping has taken place adjacent to the bridge, the ground quality has not been ideal, due to a combination of large amounts of mud, groundwater seepage, buried bricks (possibly fromwhere the bridge has been rebuilt in the past), and the presence of tree roots, where several large trees had been growing in the channel before clearance. As the shaping moves away from the bridge, hopefully these will cause less of an issue. The section shaped this month definitely seemed easier to shape.
The towpath wall again saw good progress, but again with a step backwards. As with last month, a section of wall had been identified that had been subject to frost damage and movement of the concretebehind the sheet piling. A single volunteer spent three days removing the damaged portion of wall. We think he enjoyed it, as it gave anopportunity to exercise his destructive element! The length of batter wall from Pryces Bridge has now almost reached the section of vertical wall near the centre of the length. A group of wall builders worked hard on this section, and completed it to full height, and backfilled with limecrete over a distance of about about 20 metres. The vertical wall adjacent to the culvert was finally completed, save for a small section left to be backfilled. This section has been built almost entirely by a single volunteer to ensure a single more orderly style, who has treated it as a personal mission.
At Redwith Bridge work on the fence continued, after the plan had been altered to make it even longer! The change of plan was to make the fence link up with existing fencing, rather than the hedge, which has yet to regrow to fence height, having being relaid last year.
Elsewhere, much work took place which won't directly form part of the finished canal, but is necessary to ease the tasks that are yet to come. When the channel shaping starts over a greater distance, the level of the ground will be lower than our current drainage channel, so in order to keep the drainage channel working effectively, the channel will be dug deeper over its length. For this to happen, two of the three bridges we have in place across the drainage channel were removed, the drainage dug deeper, then the bridge rebuilt, stronger than before, as we now know that we'll have hundreds of dumperloads of spoil to go over them, with each loaded dumper weighing 4.7 tonnes.
Finally, the spoil heap received some initial landscaping. There was a large section of topsoil in the centre of the spoil heap. When the spoil heap gets filled, it will be with a mixture of sub-soil, stone, silt,tree roots and other assorted stuff. In order to prevent having low-grade soil on the finished field, burying the topsoil, the topsoil was moved to one side, so that it can be used to cover the finished ground.
|Long straw..||Short straw|
|Channel profiling at Pryces||Wall building using profiles|
The vertical stretch
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