The third week of three WRG Summer Camps working on the Wey and Arun Birtley Lift-Bridge project
20-27 July 2019
For our 2019 Summer camp, we took on the third of three WRG Camps working on the Birtley lift-bridge project. This is one of two new bridges being installed on the northern reaches of the Wey and Arun to open up a half-mile or so circular walk between the canal towpath and the existing long-distance footpath which follows the old railway line which runs parallel to the canal along the valley. This first bridge simply replaces an existing farm access causeway, but the second bridge is more logistically challenging as it will replace a causeway which takes a bridleway and gas main across the canal.
The bridge design is a reinforced concrete channel, brick-lined above the waterline. The Newbury Working Party Group (NWPG) who have a long association with the Wey and Arun took charge of the first week and made great progress fabricating all of the complex reinforcing elements and shuttering required for the build, culminating in casting the base for the structure.
The second week was lead by Rob Nicholson, who was the design engineer for the structure. This week cast the East abutment, the lifting structure supporting pillars and began the blockwork for the wingwalls.
So the task for our week was to cast the west side abutment wall, continue the wingwall construction and begin backfilling the east side to form the approach ramp to the bridge deck. As with all Summer Camps, a full write up appeared in the WRG Navvies magazine, which is reproduced below:
Camp Report 201909 – Wey and Arun, Birtley Lift-Bridge Project; Week 3 of 3 – Kescrg Carries On
With reports of the first 2 weeks elsewhere in this issue, I will avoid describing the background or design of this exciting project in too much detail- suffice to say the progress from the site visit at the start of July (a big hole in a dammed-off section of canal in a field in darkest Surrey) to the start of our camp a little over 2 weeks later was dramatic. The volunteer part of the project is to construct the bridge narrows to Wey and Arun broad-beam dimensions – effectively a reinforced concrete U-section, brick faced above water level, with wingwalls angled back to the original banks of the canal, so contractors can install the metal lift-bridge structure at some point in the not too distant future. On arrival for our camp the base slab, lift-bridge structure foundation pillars and one main wall had been cast, the main skeleton of reinforcing stitched together, and all four wingwalls had been set out and were a couple of courses of blocks up. The goal for our camp was to basically progress as far as humanly possible. ‘Finishing’ seemed a bit beyond us given the critical paths in the various concrete pours required to cast the detailing for the top of the walls to take the bridge hinge mechanism on the towpath side and ‘landing zone’ in the other – not to mention the unseasonably-for-a-British-summer hot weather forecast potentially compromising our safe working hours – but ‘complete to water level’ didn’t seem unreasonable…
The nice thing about running a ‘follow-on’ camp is not having to worry about collecting Vans from across the country, finding hall keys etc. So, after meeting our catering maestra Eli at the hall and a quick afternoon site visit with my assistants Ian and Ed, we settled in to greet the arriving volunteers. It quickly became apparent that we had a great mix of ages, experience and background, including returning volunteer Brian, whose last dig was in the late 70’s … he even bought his old hard hat (who knew they even had them back then?) – but sadly it couldn’t pass the site test, as it didn’t even have a date of manufacture stamp. An interesting relic though (the hard hat, not Brian)- even older than my Sunday-best Kescrg T-Shirt and site jeans.
So, following the Saturday evening prerequisite safety video and detailed site-specific induction provided by local project supremo Dave Evans, dinner al fresco on the terrace and a light evening in the pub, it was off to site on Sunday morning to be guided to jobs by Bill (always good to have a bit of continuity from the previous weeks). This mostly involved applying thick black paint to waterproof the back of the walls constructed thus far, more block laying and concrete infill in the wingwalls, Ed leading a team setting out scaffolding (all three of these became a bit of a theme for the week) and an away team repairing a causeway over a stream in the neighbouring field to maintain access for the farmer as works progress.
On Monday, and for the rest of the week, we were joined on site by Dave Evans which was invaluable for such a technical camp. The shuttering went up for the second wall of the bridge narrows, more scaffolding was constructed to provide a clear barrow-run for the concrete pour, hardcore backfill started to arrive to fill the towpath side abutment, and more concrete went into the wingwall cores.
Tuesday was the day of the big pour – and the first really hot day. We started on site at 8am to avoid the worst of it, with the aim of completing the 3.5m3 pour by lunchtime (and not being the competitive type, there was obviously no mention of the target time set by the team on the first wall in the previous week). Suffice to say in a little over 2 and a half hours of incredible team-work, a lot of water & squash and (not that anyone was counting by now) about 35 mixes and 140 (smallish- it was a long run and we didn’t want to break anyone) barrow loads of concrete, we were taking levels and waiting to see if just one more mix would do it. Not a bad effort. The reward was mixing another half-cube of concrete for foundations for the wingwall extensions where they key into the slope of the bank, then knocking off early for fish and chips and a boat trip up the restored section from Loxwood. A great evening, especially for those of us who worked on the new lock there some years ago.
Due to the high temperatures, the shutter had to stay on the big pour for at least 48 hours, so Wednesday and Thursday involved more backfill with brick rubble, more wingwall block work, and trimming the wingwall reinforcing to the eventual profile of the approach ramps, including finishing off stitching in the horizontal reinforcing bars and planting a whole plethora of mushrooms. Thursday being the hottest day on record, we again started at 8am, and knocked off once we’d removed the shutter and had lunch. We retreated to the cinema to watch Toy Story 4 (I didn’t cry, honest) in the hope that the air con would at least keep the edge off the furnace. Ted may or may not have kept his shirt on- but it was dark, so we think it was ok?
Friday was all hands to the pump to get the site set up and ready for the local team and visiting groups to make easy progress on weekend visits – scaffolding was rearranged and installed on all 6 wall faces to allow brickwork to commence (in the local speciality Flemish Garden Wall bond), block work was laid as shuttering for the next big pour for the hinge shelf on the towpath side, the compounds were tidied, huge stacks of spare and yet to be used rebar were sorted, ‘stuff’ went into a skip and generally the site was left as you might hope to find it.
So, in conclusion – all construction is complete to water-level, and on the towpath side the backfill is to water-level, block work is complete to the finished approach ramp profile on the inside of the wingwalls, brickwork has commenced and is well progressed on 2 of the walls, and Dave was very, very happy.
A big shout out to our two brilliant French volunteers, on their second week on the site still full of energy and enthusiasm; to Aaron our 1st class D of E-er; David for spending probably a little too long in a very hot excavator cab loading dumper after dumper of hardcore, and otherwise being his usual very competent self; Lucy and Anne for excess Dumpering; Phill for blocking, blocking and then blocking some more; Ian and Ed for invaluable Assisting; everybody else for being absolutely fab and so hard working and of course to Eli for keeping us alive. It may be a stereotype, but when the French contingent compliment you on your food, you are definitely onto a winner.
And in the absence of much else to do in a sleepy West Sussex village of an evening, we are indebted to the Rainbow Ralphing Cat and his chums for the entertainment.
Kescrg are back at Birtley bridge for a joint weekend dig with London WRG on the 31st August / 1st September, and NWPG will be visiting shortly after that. All bricklayers (and anyone else) very welcome, contact me or Bill for details – or Dave Evans if you are local enough to join his regular team.