The Somerset Coal Canal (originally known as the Somersetshire Coal Canal) was a narrow canal in England, built around 1800. Its route began in basins at Paulton and Timsbury, ran to nearby Camerton, over two aqueducts at Dunkerton, through a tunnel at Combe Hay, then via Midford and Monkton Combe to Limpley Stoke where it joined the Kennet and Avon Canal. This link gave the Somerset coalfield (which at its peak contained 80 collieries) access east toward London. The longest arm was long with 23 locks. From Midford an arm also ran via Writhlington to Radstock, with a tunnel at Wellow.
A feature of the canal was the variety of methods used at Combe Hay to overcome height differences between the upper and lower reaches: initially by the use of caisson locks; when this method failed an inclined plane trackway; and finally a flight of 22 conventional locks.
The Radstock arm was never commercially successful and was replaced first with a tramway in 1815 and later incorporated into the Somerset and Dorset Joint Railway. The Paulton route flourished for nearly 100 years and was very profitable, carrying high tonnages of coal for many decades; this canal helped carry the fuel that powered the nearby city of Bath.
By the 1880s, coal production declined as the various pits either ran out of coal or were flooded and then closed. In 1896 the main pump at Dunkerton, which maintained the canal water level, failed. The resultant lowering in level meant that only small loads could be transported, which reduced revenue, thus the canal company could not afford a replacement pump.
The canal became disused after 1898 and officially closed in 1902, being sold off to the various railway companies who were expanding their networks.
In September 2014, restoration work began on the canal section from Paulton to Radford, with the aim of restoring the northern branch from Paulton for navigation in the future. The largest canal drydock in England has been revealed at Paulton and culverts and bridges nearby are being reinstated or rebuilt;. About of canal from Paulton to Radford was re-watered in mid-2015, but a leak resulted in that section drying out again.
History
Background
The Somerset coalfield had been producing coal since at least 1437, when the main source was a pit at Kilmersdon. By the early 1500s, additional pits had been opened at Clutton, High Littleton and Stratton-on-the-Fosse. There were also mines at Farrington Gurney, Midsomer Norton and Paulton by 1678, but no mining activity at Radstock. This changed in 1793, when an exploratory shaft found coal seams at varying depths below the village, which led to a flurry of new mines opening at Dunkerton, Foxcote, Priston, Timsbury and Writhlington. For all of the pits, transport was a major problem because of the poor state of the roads. The cost of getting the coal to market, and the threat of cheaper coal from south Wales as a result of the opening of the Monmouthshire Canal, which was then under construction, led to the proposal for a canal which could transport Somerset coal to Bath and Wiltshire.
Initial surveys were conducted during 1793 by William Jessop and William Smith under the direction of John Rennie who presented a report on 14 October 1793 estimating the cost of construction of the canal at £80,000. Smith, who also worked at the Mearns Pit at High Littleton, made the original observations leading to his important stratification theory by observing the dips in the geological strata through which the canal was cut. Smith became Surveyor to the company, but was dismissed in April 1799, apparently because he had used his position as surveyor to buy a local house at advantageous terms. He then set himself up in a private practice in Bath but was re-engaged by the company in 1811, to provide advice when repairs became necessary to the canal bed.
As there were no serious objections to the plans, passage through Parliament was smooth, and the canal was authorised by an act of parliament, the (34 Geo. 3. c. 86), which received Royal Assent on 17 April 1794. It was entitled "An Act for making and maintaining a navigable Canal, with certain Railways and Stone Roads, from several Collieries in the county of Somerset, to communicate with the intended Kennet and Avon Canal, in the parish of Bradford, in the county of Wilts". Rennie then had doubts about his original route, and suggested it should be constructed at a higher level, to avoid a long tunnel at Combe Hay. William Jessop was asked to check the new route, and with Rennie gave it his approval, assuring the committee that there was an adequate water supply for the change.
Further detailed surveys were carried out by Robert Whitworth and John Sutcliffe, while the committee sent Samborne Palmer and Richard Perkins, accompanied by Smith, on a fact-finding tour of the canals, inclined planes and tramroads of England and Wales, to help them decide whether to construct a canal with inclined planes or railroads. After they reported their findings on 3 October 1794, the committee decided to proceed with a canal or railway. Sutcliffe was then appointed as chief engineer, and in January 1795 the committee finally agreed that a canal would be better than a railway. Its route was not resolved until they obtained a second act, the (36 Geo. 3. c.46), which authorised variations to the route defined in the original act.
Construction
In May 1795, tenders were invited for the first sections to be built from Paulton to Hopyard, Camerton and from Radstock Bridge to Peglinch in Wellow. An estimate by the contractor Houghton & Son from Shropshire was accepted and work began. Part of the Paulton route was sufficiently advanced that five boats carried coal from Dunkerton to Camerton on 1 October 1798, some of which was then delivered by road to Bath.Bath Georgian newspaper, 4 October 1798
On the northern branch to Paulton, there was a difference in levels of to be overcome, and this was concentrated at Combe Hay Locks. Rather than use a flight of around 23 conventional locks, the committee elected to use vertical boat lifts. Perkins and Palmer had seen various lifts during their fact-finding tour, but most were designed for small boats, whereas they wanted one that could transport full-length narrow boats. They considered building railway inclined planes, and using railways rather than canals for the upper levels on both branches. However, in 1794 Robert Weldon proposed using his vertical lift, known at the time as a hydrostatic lock but later called a caisson lock. The Kennet and Avon Canal agreed to fund one quarter of the cost of an experimental lift, and Weldon was asked to build it on the Radstock branch, but the site was later changed to Combe Hay. If it worked, Weldon would be paid £200 for use of his patent, but nothing if it failed.
Weldon had built a model of his design at Oakengates, next to the Shropshire Canal. He started work on the first of three caisson locks which would be required at Combe Hay in early 1796. A narrow boat laden with 20 or 30 tons of cargo would be floated into an airtight wooden box, which was submerged in water in a stone-built cistern. The buoyancy of the box counterbalanced the weight of the boat and its cargo, and the box could be moved up and down by racks and pinions. Construction continued throughout 1796 and 1797. Meanwhile, tenders were awarded for building the canal from Midford to Limpley Stoke, and the junction with the Kennet and Avon Canal. During the first trial of the caisson lock in February 1798, the rack and pinion mechanism broke. After repairs were made, another trial took place in June 1798, when a boat was successfully lowered the down the lift, and raised back to the upper level. Weldon pledged that he would demonstrate the lock by using it to transfer 1,500 tons in 12 hours, using just a lift operator and a boatman. The committee decided to build two more lifts, one at Combe Hay and one at Radford, but no work was undertaken until the final trial had been completed. It never was, as there were repeated failures, and the committee started to consider other options.
Three successful trials of the caisson lock were made in April 1799, but the walls of the chamber started to bulge. The Bath Herald reported that the leakage from the cistern was so bad that the lock could only be used for three or four hours before trials had to be abandoned. While they blamed the masons who had built the faulty cistern, it was probably the ground in which the cistern was built that caused the problems. It was built through Lower Fuller's Earth clay, a material that is notorious for expanding when wet, and this would have exerted enormous pressure on the cistern walls. At the time, the process of making waterproof cement was also in its infancy. These two factors caused the walls of the cistern to bulge inwards, resulting in the caisson jamming. Smith may have known of the problem, since he had visited Sapperton Tunnel on the Thames and Severn Canal in 1788 and 1794, which was distorting where it was cut through Fuller's Earth. After years of fruitless searching for the site of the lock, an archaeological dig in 1997 confirmed its likely location, following the discovery in the Public Records Office of a map dating from 1804-1806 showing the caisson and its exit tunnel.
Nobody responded to a call for tenders in 1799 to rebuild the lift and to build the others. In the same year William Whitmore and his partner, Norton, offered to build a balance (or geometrical) lift without payment, on condition that if successful they were to have £17,300 and a royalty of 4 pence per ton on goods passed. Sutcliffe suggested that it was a better design than the caisson lock, but was unsure that it could be built large enough to handle boats of 24 tons. He was also aware that James Fussell was building a similar lift on the Dorset and Somerset Canal, and recommended that they wait to see how successful that was. Benjamin Outram was asked for advice, and suggested that the colliery railways should be rebuilt as plateways, to take much larger trucks, which could then be shipped down the canal on rafts, which would be and would carry 12 trucks. The trucks would then be lowered down a plateway incline to more rafts on the lower levels, or the coal could be loaded into boats.
Sutcliffe was critical of this suggestion, as it would require the canal to be widened, and he thought Outram had grossly underestimated the cost of the work. He advocated a flight of locks at Combe Hay and Radford. Outram then suggested that railway inclines could be built at both locations, with coal carried in boxes on the boats, which would be transferred to the railways by crane. The inclines would be counter-balanced, with full boxes descending being used to raise empty boxes or boxes part-loaded with other commodities. This solution was adopted, and three locks were built below the Combe Hay inclined plane to lower the canal to the Midford level. The plane was not a success, with the Kennet and Avon company complaining that the coal was damaged by the transfer, and the Wilts & Berks Canal company complaining that the transfer was slow and costly. The committee therefore decided to build a flight of 19 locks at Radford, and an additional 19 at Combe Hay.