During September we were mainly casting the intermediate stability base and wall-reinforcing concrete slabs between the ones cast by the Waterway Recovery Group (WRG), in the two weeks they were with us for their summer camps.
We had to decide how to complete the first ten metres (or two sections) next to the London Road bridge. This was because the WRGies had dug out in front of the Big Pipe and there wasn’t enough space to get a machine anywhere near – we couldn’t squeeze it in between the pipe and the towpath wall.
There were two potential solutions – leave things as they were or import some ramp material. The first option would require a huge amount of work filling the base and shuttering with barrows full of nine cubic metres of concrete, tipped from the towpath. So we went with the second option of placing ramp material in front of the pipe to take us back to the level of the pipe, enabling us to access the area with our machine, five metres at a time.
This meant that our volunteer team could get on with casting the reinforcing wall, and we could continue to extend the foundations of the offside wharf wall as well.
With all the transfer of material, it took us over six weeks to deal with that first troublesome ten metres of base and reinforcing wall.
Things progressed more quickly from November onwards, because we hired in a second set of shuttering, but then the weather became much wetter and we had to contend with lots of mud.
The soft ground caused by the rainfall brought further problems (ironically on our last vertical pour) as some of the shuttering support fixings tore out. So we are now progressing remedial action.
At the time, we hastily added additional propping and counter weights to try to prevent further movement. We also stopped filling that section with concrete as soon as we saw the shuttering fixings start to move.
We know the cause and have learned from it, so we can now guard against it happening again if we have further work like this. However, on reflection, the overall outcome of this first eighty-metre section is not at all bad for a group of volunteers, who have mostly never done this type of heavy manual construction work before and when you factor in our age profile.
By mid-December we’d progressed quite well, having cleared away the ramp material again, and restarted casting the base slabs.
The next stage was to prepare for contractors to come in and help.
Mike Babb
Workparty volunteer
This blog first appeared in Cut Both Ways, our members’ magazine, become a member to get your copy.
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