More clay, a slipway and a concrete base
As 2015 began our work party's attention was focused on Summerhill - more on that elsewhere. Even so, work started on a canal concrete base and that continued through the year.
Why concrete? In the old days Navvies used to lay clay along the canal bed to prevent water loss. In those days labour was cheap and plentiful and large areas could be done at a time. Today however with only our small volunteer force to do this task we have to do it differently. When clay is laid it has to be kept wet. If it dries out it will crack and will not be any use for retaining water. Therefore we now must work on smaller areas at a time and have water available nearby with which to keep any newly laid clay wet. It also requires a massive amount of clay to be laid, with a recommended depth of 600mm.
We must now work along pound 27 in small sections. Once the concreting has been completed, the 'Big Pipe' can be taken out for say 40 to 50 meters. Concreting under where this pipe was then needs to be done. There is to be a clay infill between the concrete base and the base of the towpath wall. This infill measures approximately 1.5 meters wide and 0.5 of a meter thick. A clay platform is required so that if the canal water level falls any boats tied alongside the wall will just sink down onto that platform.
So, once all the concreting is done and the clay platform laid, and the bank opposite the towpath made waterproof we have to make a temporary dam from side to side. We can now flood the first section. Job done! The next section can now be prepared. Another length of the 'Big Pipe' can be taken out, say another 30 to 40 meters. Any flood waters will need to be channeled back into the big pipe again until these preparations are complete. The black pipe alongside the towpath wall has in the mean time been keeping the minimum permitted flow of water from pound 26 to the weir We then build the next dam a further 30 to 40 meters towards the weir and remove the first dam. So we now have two sections in water. And this sequence is repeated until we reach the weir down by the A38 corner.
By March the team were back in force at Tamworth Road. The dry conditions allowed us to move a lot more clay down to the winding hole but we still have problems actually spreading, levelling and compacting the stuff.
Work started on a slipway just below Lock 26. This will be essential if we are to hold the planned IWA Trail Boat Festival in 2018 (subsequently this ambition was put on hold but the slipway will still be a useful feature).
By mid-May great progress had been made in the slipway area, with brick-and blockwork already well advanced, more concrete laid and more ground prepared. In addition a lot of effort has gone into grass-cutting and strimming; the whole area looks very smart.
The slipway is shuttered and the reinforcement in place ready for a load of ready-mix, after which it only remains to build up the wing walls and another important part of the jigsaw will be in place.
June - The slipway wall
Most of our activities were centred around the slipway, where our normal wall construction methods, although a little slow, result in a very strong structure. In this case we build up a back wall of concrete blocks and a front wall of blue bricks, a course of headers and 3 courses of stretchers, filling the sandwich with reinforced concrete. By Mid-June the wing walls are almost up to the level at which we can lay the bull-nose top courses, after which it only remains to do the last bit of backfilling and tidy up the surrounding area.
The slipway was completed, the last brick laid, the last concrete poured, at the end of July.
More concrete slabs have been laid alongside the big pipe ready for its removal in, we hope, the not-too-distant future. Another important job has been the installation of a by-pass pipe from Lock 26 to the weir corner; this will provide the required dry-weather flow when we start to remove the big pipe.
August - the base advances
The concrete base is progressing at a relentless pace, although a slow relentless pace. About 4 metres a week in fact. We are now nearing the access ramp half way down towards the weir. Then we will have to continue working on the far side of this access ramp leaving a short section to be concreted after the big pipe is removed.
Soon we will be wanting to place, and work, clay alongside the towpath wall to form the seal between the concrete and the wall and form the platform for boats to rest on should there be a fall in the canal's water depth. A quantity of Hessian sand bags have been sourced, these need filling (2/3rds) and will be used to construct the temporary cross canal dam when we flood the first section.
This latest area now gives us an insight into to the task of lining, waterproofing and protecting this off side bank. We need to achieve a bank with a 2:1 batter (slope to the uninitiated) that is waterproof and will withstand the battering that the narrowboat brigade will undoubtedly give it We need to decide on this so that when the 'big pipe' is removed we know what we are doing and can proceed with the re-watering without delay.
October - the pipe is still an obstruction
Terry Brown made a good start on breaking the concrete around the 'big pipe' just below lock 27, but the concrete in places was at least 2 feet thick and it was hard going. The concrete cap on the inspection chamber half way down the 'big pipe' towards the weir was dislodged an awaits the attentions of the concrete breakers to break it down into smaller manageable pieces.
More progress was made on the concreting of the canal base in pound 27. Dried up clay that had been spread out on this concrete base and rolled to break the lumps had re-hydrated nicely with the rain. In fact almost too much so. I can see that this clay thing is going to tax ones patience in getting it just right. Too little water making it still crumbly and render it useless as a water barrier, too much water in its consistency will cause it to be unable to hold its shape.
Other work on the site saw progress on the levelling of the bank on the left hand side to correspond to the height of the towpath. This will enable us to dress this bank to the required 2:1 batter when we have a digger capable of the task.
November - records are broken
November 25th saw a record-breaking turnout of volunteers. Our own regular workforce, this week there were seventeen of us, was supplemented by five able bodied men from Walton Homes.
Every one appeared good and early and by 10 am the concrete mixer was already in full swing. During the day a record length of concrete was laid, about 12 meters, this brought the concrete base to within another good days work to the weir,. The area around the weir itself is very wet and I fear that we will either have to wait till we have another dry spell or lay a hardcore base before we can concrete the last bit.
Also we moved clay from the storage area to the far side of the 'big pipe' for re-hydrating, where the Waker roller was put into good use to break down the hard lumps within the clay.
December - Wet but business as usual
Another good length of canal base was prepared and the concrete laid. Concrete was also poured in the corner where the towpath swings round towards the A51. This left a rather short section of the canal base still awaiting concrete. With all the flood water the black pipe had clogged up and needed attention.
Bob W and crew completed the last bit of concrete down the towpath side. (One can almost hear the Champagne corks popping). But , sorry chaps , there's a lot more to do yet, and it will be hard work with that 'big pipe' still there impeding our progress.
The following week the ground was still pretty water-logged which made the going hard. Deliveries of more clay, more sand/ gravel mix and cement bags came on time. In the morning we were able to strike the previous concrete pour's shuttering and reassemble it just in front of the pipes leading into the weir. The concrete mixing gang swung into action after lunch and so another block was soon laid.
A new year and we keep plugging away
In January and February 2016 in spite of the weather the majority of our labours have been involved in either preparing and laying concrete down by the weir or establishing a proper track along the top of the canal bank on the Tamworth Road side.
Down by the weir we were struggling to find stable subsoil on to which we could lay the concrete. A few dry days would have made all the difference, but no such luck. However we did manage to extend the area already laid and just past the weir we have reach the limit of the concreted base.
The other major job was to establish a firm durable track from our compound down to the winding hole along the top of the earth bank. At the same time dressing the top of this bank to an even height in preparation for the laying of the Concrete Blanket. Great progress has been made on this job and as I write this blog we must now be 80% of the way. This roadway is essential for future access and to allow clay to be delivered to the winding hole.
By the end of February great progress was made with the continuing construction of the roadway along the top of the left hand canal bank which is nearing completion. And at last, this Sunday just gone we were able to lay another sizable area of concrete in spite of a weather forecast of severe frost.
Spring is in the air
With the longer days and warmer weather returning, on Thursdays and the weekends volunteer numbers grew.
During this period we continued to lay concrete down by the weir. At the other end of the big pipe we removed one section that we had temporally replaced. This enabled us to prepare a fairly large area under and around where this section of the pipe had been,for concreting. We needed this to be completed on the first Wednesday as we had committed ourselves to replacing this pipe section by the end of the weekend, and concrete takes a good few days to mature.
We did have a flood situation mid-March after heavy overnight rain which made working pretty impossible.
Never the less, over this period we laid more concrete and continued shaping the batter to the marina side of the canal, and at the head of the big pipe by lock 26 we are taking measures to improve the run off into the pipe after heavy rain, this work includes resetting one of the sections of the big pipe which had become dislodged. The Land Drainage Consent application has been formally submitted and we await the consent from the SCC Flood Risk Team and we can then remove the big pipe !
And now for something completely different...
Something called Concrete Canvas, something that we are pioneering on the earth bank that is on the Tamworth Road side of the canal.
What is it? Well its about 5 mm thick and consists of a waterproof membrane on one side (the underside), and a fabric membrane on the top side. Sandwiched between these two membranes is a fine dry powder that is similar to a fine concrete mix.
Now all we have to do is lay it onto the earth bank where it naturally takes the shape of the earth below. We then wet the Canvas and within a few hours or so the material is set rock hard. The Concrete Canvas comes in rolls 1 metre wide. We lay it with an overlap of about 100 mm. using a specialized grout to seal between sections. And Hey Presto! we have a waterproof lining. Now, as the canal will eventually see narrowboats chugging up and down and no doubt hitting the side from time to time we have to protect this lining from damage so a 75 mm thick layer of concrete has to be laid over the Canvas. It is great to see this lining starting to progress towards the A38.
The clay at the bottom of the towpath wall is getting puddled in (reluctantly), its a mucky sticky job but has to be done and now with the weather neither too dry or too wet its a good time to do it.
Into May with a to-do list
Very soon a start can be made on the removal of the Big Pipe. With this out of the way we can really crack on with our aim this year to get pound 27 into water. The trouble is, there are still a tremendous number of things to be done. These include:-
● completing the Concrete Canvas lining
● the concrete reinforcement
● installation of the geomesh above the concrete reinforcement
● concreting below where the big pipe was
● the clay bank below the towpath wall
● the supply and installation of the penstock by the weir
● capping the C.C. bank with dry concrete filled sand bags
● making a shallow dam at the mouth of the winding hole.
This dam will enable us to concentrate totally on the pound 27 works. And it will provide an essential source of water to wet the clay in the winding hole when we come to line it.
'Big Pipe' removal day - May 11th.
It was a long time coming but finally removal of the Big Pipe got underway with the guys moving about 20 sections per hour using a Telehandler on loan from Finning Equipment Solutions at Cannock.
This great achievement is a significant milestone in the restoration of this section of the Lichfield Canal and with its removal our volunteers can now carry on with the remaining canal lining along the bed of the canal which has been prevented by the pipe being in the way.
By the end of the first day all but the last eight sections had been removed. However, on Day 2, the last few sections proved to be more of a struggle. The concrete strip at the far end is too narrow for the Telehandler. If it goes partly on the conctrete and partly in the hole where the pipe used to be it may tip over. Meanwhile we are tidying up and over the next few days will transport the pipes to the section of canal where they will be recycled for use as part of the canal retaining wall supporting the Heritage Towpath Trail.
The following day Tony Gardner in our larger digger was able to get to the remaining big pipe sections out so that Keith in the Telehandler could reach them comfortably. Finally, with a combined effort from Keith on CAT Telehandler and Tony Gardner on our own 5t Excavator the last section of Big Pipe was wrestled from the canal bed and brought out to the stockpile. We had loan of this machine only till Tuesday so good use was made of it to now move the pipe sections to a storage area beyond the narrows and the A51.
Wednesday May 11th was 'Big Pipe Day'. We had been looking forward to this for a long time! Peter Buck describes the action.
June - More concrete and a celebrity visitor
With the euphoria of the pipe removal now past it is apparent how much work there is still to be done to achieve the target of watering pound 27, if only as far as the winding hole, before the end of the year.
We have made a good start on concreting the base of the canal from both the lock end and the weir end.
We had a long awaited visit from the E.A. with regard to a disputed impounding licence. The outcome of which was that they required water flow readings from the outflow of the remaining big pipe.
Our Vice-President David Suchet paid us a visit just short of eleven am on June 17th. He spent a good hour with the team chatting and photo taking. He said he was most impressed with the progress since he was last on a canal visit some ten years previously.
August - the pad is complete at last
With the end in sight Hugh decided to order in a delivery of 'mix it on site' concrete from Moody's. On Wednesday 27th at 11 o'clock the delivery arrived and by lunchtime it had been laid, tamped and trowelled with a whole lot less effort by our workforce. All 6.25 cubic meters of it! This has left just a small area of concreting still to complete, perhaps another 7 cubic meters, booked for 11 0'clock on Wednesday 3rd August.
And so that finishes the base. There is still a lot of concreting to do in reinforcing the canal bank batter. But although time consuming this is not such a slog that the canal base proved to be.
A timelapse video made from photos taken by Christine Howles over the period from July 2015 to September 2016, including the removal of the Big Pipe.
Puddling clay in the winding hole
A 13 tonne JCB digger had been offered to us on free loan for a long weekend from 18th August till 23rd August. Chase Civil Engineering deserve our grateful thanks for their generosity. To make best use of this opportunity we had taken delivery of load upon load of puddling clay. The JCB made easy work of placing this clay where it was needed and of compacting it. Tony Gardner thought he was in heaven with this big monster under his capable control.
Getting the clay in the winding hole was a huge step forward. Stop planks were sourced for the narrows and installed. Now all that remains to be done before water can be introduced is the delivery, assembly and fitting of the 'penstock' in the weir. However the gang created a low dam around where the penstock is to be fitted and when we had the heavy rain of a few days ago the water in the winding hole was nearly knee deep. It's beginning to look more like a canal.
With the concrete reinforcement of the left hand canal bank batter completed we could start on installing the Geomesh to the top half of the batter and the capping sandbags which are to be filled with a dry concrete mix. We also provided some fishing pegs for disabled anglers along the top edge of this bank. All we need then is lots of water and some fish in pound 27.
Earlier in the year a mix of Bream, Carp and Rudd had been introduced to Borrowcop Locks Canal Park. This allowed us to host a well attended Family Fishing Day on August 6th. Read more here...
Recycling the big pipe
Another major undertaking we have embarked upon is the cutting down to size of the redundant big pipe segments. These segments are 3 meters long. We are cutting off one meter from each pipe, and there are sixty plus pipes to do. Why? well the long remaining piece is to be used to form part of the towpath wall between the narrows and the A51 tunnel, and 2 meters is a better length to manhandle and is still long enough. The cut off one meter length is going to be taken over to Darwin Park where the 'Wergies', the Waterways Recovery Group volunteer force, will use them to establish and extend the noise sound barrier at the side of the A38 some time in September.
September - Time to go Geomeshing
At last we have completed the concrete reinforcing half way up the left hand canal bank batter, which is lined with Concrete Canvas. Why have we only gone halfway up? Well, its all to do with the hull shape of a typical canal narrow boat. Most boats are slab sided, a vertical plate that reaches approximately 600mm plus below water level before it is welded to the flat bottom base plate to form a fairly sharp edge along the length of the barge. This edge would, if not protected by the concrete we have been laying, easily damage the Concrete Canvas and cause the canal to leak badly. As this sharp edge is so far down into the water it is not necessary to concrete right up to the top. This leaves the top portion available for water plants and grasses to grow. To assist them we are stitching a Geomesh matting to the top half of the batter. This will trap silt and hopefully plants will grow, spreading their root system into the Geomesh and make the canal look established.
Following the completion of the concrete reinforcing the Geomesh is now being laid, and to secure this the top edge is trapped by sandbags that are filled with a weak mix of concrete. Also along the top edge of the bank you will have noticed that, at twenty yard intervals, fishing pegs are being provided for the specific use of disabled fishermen.
The Penstock component parts arrived and it taxed our brains as to how it could be threaded through in to the weir. All we need then is for the Environmental Agency to smile on us with the required permission to impound water and you will have a bit more that you can call a canal.
What is a 'penstock' ? The word is an olden-day word borrowed from the time of watermills. A penstock is a device that controls the flow of water such as a sluice or weir, or as in our case a gate valve. We need a penstock for two reasons, the main reason being that by controlling the water flow through it to near zero we will be able to fill the finalized pound 27 with water. The second reason is that the Environment Agency need to be satisfied that we continue to supply about 1 litre per second of water though the canal into the brook that passes under the A38, which is what the black pipe down the towpath side wall does at this time.
Then in October a setback - an engineer was given the job of doing a few alterations to the pipework. However, the unfortunate engineer had his van stolen a few days after taking our pipework away to his workshop and unfortunately for us our pieces of pipework and a hefty gate-valve were in the van! So back to square one, to source more parts. Once we'd got them it didn't take long for them to be assembled and installed into the weir. The canal pound 27 end of the penstock has been sealed between it and the big pipe with concrete and we are now in a position where we can regulate the flow of water out from the canal.
November 22nd - Regular walkers along the adjacent Heritage Towpath Trail, which also forms part of the Heart of England Way, were amazed at the sight of the canal pound filled with water for the first time in over 50 years.
The Trust had already been working closely with the Environment Agency to allow water to be stored within the canal, but the extreme water run-off from Storm Angus resulted in the canal pound being filled in only a few hours, delaying the arrival of the floodwater peak downstream and reducing the flood risk.
The floodwater from Storm Angus stored within the canal pound then drained down naturally through a temporary pipe, pending agreement of the final control structures with the Environment Agency.
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