This project restored 450m of channel between Redwith Bridge and Pryces Bridge during the period from March 2008 to June 2014.
British Waterway’s contractors had previously cleared the bed of the canal, installed a culvert and constructed a piled towpath along the length. We had the good fortune to inherit the contractor’s compound and hard-standing. Our tasks were to face the towpath bank with a stone wash wall along the full length of the section; build a 130m long stone faced reinforced concrete retaining wall on the offside; and to shape, line and block the channel. The monthly work parties were of two days duration with a very occasional third day added to pump out the site.
The towpath structure had been piled to just below eventual water level, waterproofed and capped with concrete before our involvement. Starting in March 2008, added to this structure was a sloping (‘battered’) wash wall similar to the some of the original examples on the canal. This required the development of a setting out method since both the curve of the bank and the slope of the wall mean that conventional string-lines could not be used. The solution was the use of close spaced portable wooden profiles which clipped over the edge-board of the towpath to accurately locate the front face of the wall by sighting between them. The wall was constructed of stone recovered from elsewhere on the site or imported, the stones being bedded in lime mortar. A pattern of working emerged in which a course of the batter wall was completed followed a day later by backfill with ‘limecrete’, a version of concrete which has lime in place of cement. The latter had all the working properties of concrete but, importantly, also has the same rate of expansion and contraction as the mortar. The limiting factor on progress was the production and supply of mortar and backfill. A large gang worked constantly on mortar production and transport duties throughout this phase of the works. For much of the time this involved production of four different mixes to order (concrete or mortar with either cement or lime) and shifting it around a site. At the start of the work on the wall there was a concern that the repetitive nature of the wall building work might deter volunteers. Fortunately the reverse was true and the volunteer numbers increased steadily over the course of the project. The wall was eventually finished in October 2010.
Work commenced on the offside wash wall at the start of 2009. This structure extended 130m south from Redwith Bridge and consisted of a reinforced concrete base on which was located two high density concrete block/cement mortar walls. The volume between the walls was filled with reinforced concrete and the front of the wall above the eventual waterline faced with stonework similar in appearance to that on the towpath. A considerable amount of excavation was required to construct the base and this presented a problem since the equipment available was a 3 tonne excavator and a 1 tonne dumper, both owned by the society. It must be remembered that hitherto the Society had worked solely on structures such as locks which required neither excavation machinery nor personnel trained in earthmoving. It was realised that this was but the first of many earthmoving jobs so in mid-2009 the number of trained excavator drivers was increased and a number of volunteers trained on tracked dumpers. This in turn permitted larger capacity hired equipment to be used for earthmoving. These were first used to excavate the wall foundation, after which the wall base was shuttered, reinforcement placed and concrete pumped from the compound in June to complete the task. Another piece of reinforced concrete construction that summer was an invert at Pryces Bridge together with a small section of adjacent wash wall.
Shaping of a short section of the channel commenced in mid 2009 at Pryces Bridge, after which it was lined using a bentonite liner. This proved very difficult to use. It was heavy and was intended to be handled on rolls using specialist machinery not available to volunteers. We were thus restricted to the largest sheets that could be lifted and manoeuvred manually. Transport required care to avoid splits and the joints needed careful treatment with a special gunge. The other big problem was the need for an overburden to counter the expansion (15 times) of the hydrated bentonite. For this, on-end high density concrete blocks laid on top of the liner were used. This produced a high quality finished product but the large number of operations meant that it was very labour intensive, time consuming and expensive.
The solution to the lining problem came as a result of a site visit from a number of British Waterways engineering staff, led by Les Clarke. During the day Les mentioned that he had been approached by a representative of a company offering a new type of lining material that potentially replaced both the bentonite and the associated geotextile, and required only minimal overburden. The significance of this was immediately appreciated by the Society members present and it was agreed that was something worthy of further investigation. The ‘new’ lining material was essentially a version of the lightweight non-woven geotextile we had used previously, but factory-treated with an acrylic waterproofing chemical. On contact with water, the acrylic reacts and swells to form a stable waterproof gel that is self-healing when punctured. Its other property is that it does not actually need covering to work. However some form of protection was required to protect it from damage in a working canal. In our case the existing blocks could be used, but laid on their side rather than their long edge. Since all the work of cutting, transporting, and sealing the bentonite was eliminated and the blocks were laid side-on rather than end-on, this promised much quicker progress than hitherto. Thus the Society became the launch customer for this new material. The downside of being the first customer is that the production process for the material was not well established and reliable supply was initially a problem.
Shaping the channel had started in a modest way in 2009 but was constrained by the need for access to the adjacent wall building sites and the available earthmoving capability. Enough channel had been shaped in 2010 at the Redwith end of the site for the lining and blocking to start in earnest. However the problem of countering the water inflow – from both rainwater and groundwater – was not addressed. Consequently delivering the lining materials by dumper quickly turned the shaped channel into a sea of mud. This mistake was partially rectified elsewhere on the site by installing a land drain. This consisted of a perforated plastic pipe in a half metre deep trench lined with a geo-textile and filled with gravel. Sumps also made of plastic pipe at intervals enabled water to be pumped out and kept the formation free of standing water. Most of the south end of the site eventually had a land drain. The other major earthmoving jobs were shaping the sloping banks of the channel, and building about 80m of offside bank where none existed. The latter was in the centre of the section adjacent to the culvert. Progress on the earthmoving was such that by the end of 2010 with well over 100m of channel was shaped. Lining continued in 2011/12 and eventually the 130m of channel next to the offside retaining wall was finished after a prolonged battle with the mud.
The principal target for 2013 was to finish both the channel shaping and the lining operations along the whole length before the end of the restoration season. This was a pretty ambitious aim given that there was 250 metres of channel to be shaped and the neck end of 300 metres of channel to line. It was realised that there was no hope of achieving the target using the working practices of past years. The main problem hitherto had been the conflicting demands on plant and labour of the shaping and lining operations with the result that neither worked as efficiently as they could. To overcome this, separate work parties for the two operations were held and this more single-minded approach overcame most of the former problems. The other notable feature of the work parties was that the volunteers worked longer (Friday working became the norm) and more efficiently than in previous years due, in no small part, to the use of some bigger bits of plant.
March 2013 saw the start of a new monthly ‘two part’ format with a six-day long shaping work party. The participants were machine drivers, surveyors, first aiders/welfare personnel together with an impressive array of machinery; the most eye-catching item being a 14 tonne digger which had the power and reach to shape the offside bank slope in one operation. Aided by dry weather, a 100m section of channel was finished during the work party and the appearance of the channel was transformed. The notion that the new working practices were delivering was reinforced a fortnight later when a full complement of volunteers lined 34 metres of channel, easily beating the previous best. This work party turned out to be notable for another reason, namely, being the last in which blocks were transported by dumper along the bed of the canal. During the weekend successful tests were made on the Society’s ‘secret weapon’ – a home-made block chute – which allowed blocks to be transported along the top of the bank and delivered to the channel base without damage to the shaped channel bottom. Wading around in mud was a thing of the past and, wow, did it speed things up!
The two three-day work parties a month routine continued during April, May and June each with a greater output than the last. June saw the record for the length of lining laid in a weekend broken yet again. There were two major contributory factors to this – a lot of preparatory work and some very substantial reinforcements on the first day in the form of 16 members of JATCC 394 Course based at RAF Shawbury. The trainee air traffic controllers shifted a prodigious amount of blocks and jointly with the Society volunteers completed nearly 60m of channel during the day – a record that will stand for some time!
About 100m of channel remained unlined by July and it was touch and go as to whether it would be closed by the end of the year as hoped. A combination of non delivery of the lining material and the rains hindered progress. Delivery of the liner enabled normal service to be resumed in August and the lining gang worked wonders to reduce the gap to 65m. By the end of September it was 40m and by the end of October it was reduced to 20m. There was now only one more work party to finish the lining. The November work party kicked off with yet another frantic day-long pumping session. However two days of dry weather and a full complement of experienced block layers ensured that by mid afternoon on the Sunday the job was finished. We had done it with half a day to spare!
Work in 2014 got off to a spectacular start in February. A second consecutive exceptionally wet winter had left the channel with a good half-metre depth of water and for us a major problem of how to get rid of it. Happily the Shropshire Fire and Rescue Service rode to the rescue using their High Volume Pump as part of a training exercise. This beast pumped the estimated one and a half million litres of water out of the channel and under Redwith Bridge in just 4 hours. The three remaining work parties were devoted to finishing-off work: levelling the erstwhile ‘tip’ to make it suitable for agriculture again; placing rip-rap on the offside bank; remedial pointing on the stone and brick walls; and grouting along the base of the piling. By the end of May, all work was complete.
The June work party will go down in the record books as the month when the Redwith to Pryces section saw boats for the first time since 1935. The event had extensive coverage on TV, radio and in the press. Judging by the number of visitors over the weekend the canal had been magically transformed into a significant tourist destination. The first boat sported a barrel of beer on its bows – for later consumption. The evening saw a celebration at Canal Central for the volunteers who had worked on the section. The barrel of beer was duly opened and the celebrations, as they say, went on long into the night!
There is a coda to the story of the Redwith to Pryces length. It might seem surprising that a section which required the fire brigade to remove the water before work could commence was later found to leak. Water was found to be escaping both into both the brook which is culverted under the canal and into some of the surrounding fields. Subsequent investigations by CRT established that the leaks were via the piling which forms part of the construction of the towpath side. The main problem was that the waterproof membrane at the back of the piling had perished. The piling and towpath was of course the only parts of the work which the society did not do. The leaks were subsequently repaired by CRT in 2021.