Harecastle Tunnel
Harecastle Tunnel is the term referring to 2 canal tunnels on the Trent and Mersey Canal at Kidsgrove in Staffordshire. It is made up of two separate, parallel, tunnels named after the engineers that constructed them. The first, by James Brindley, known as Brindley, is 2,880 yards long, and the second tunnel, Telford, is 2,926 yards long.
The Brindley tunnel was constructed between 1770 and 1777. Brindley died during its construction. At the time of its construction it was twice the length of any other tunnel in the world. It took 11 years to complete.
To construct the canal, the line of the tunnel was ranged over the hill and then fifteen vertical shafts were sunk into the ground. It was from these that heads were driven on the canal line.
A major problem was the change in the rock type which ranged from soft earth to Millstone Grit. The construction site was also subject to flooding regularly, a problem which was overcome by the construction of steam engines to operate the pumps. Stoves were installed at the bottom of upcast pipes to overcome the problem of ventilation.
The tunnel had no towpath and so boatmen had to leg their way through the tunnel, lying on the roof of their boat and pushing on the sides of the tunnel with their feet. It could take up to three hours to get through the tunnel. The horses which towed the boats were led over Harecastle Hill via 'Boathorse Road'.
A lodge (Bourne Cottage) was built by the side of the squire's drive at the point that the boat children crossed it, to prevent them straying up towards Clough Hall.
The tunnel was twelve feet tall at its tallest point and was nine feet wide at its widest, which proved to be too small in later years. The tunnel suffered subsidence in the early 20th century and was closed after a partial collapse in 1914.
Due to the amount of traffic and the slow process of legging, the Harecastle Tunnel was becoming a major bottleneck on the canal. It was decided to commission a second tunnel to be built by Thomas Telford. Due to advances in engineering it took just 3 years to build and was completed in 1827. It had a towpath so that horses could pull the boats through the tunnel. After its construction it was used in conjunction with the Brindley tunnel with each tunnel taking traffic in opposite directions.
Today only the Telford tunnel is navigable. The tunnel is only wide enough to carry traffic in one direction at a time and boats are sent through in groups, alternating northbound and southbound. Ventilation is handled by a large fan at the south portal.
Between 1914 and 1954 an electric tug was used to pull boats through the tunnel.
In 1954 a large fan was constructed at the south portal. After boats have entered the tunnel, an air tight door is shut and all the air is pulled through the tunnel by the fan. This allows diesel boats to use the tunnel without suffocating the boaters. Today the journey takes about 30–40 minutes.
Inspections of the disused Brindley tunnel continued until the 1960s, but since that time, there has been no attempt to investigate the interior of the tunnel at any significant distance from the portals.
The gated portals can still be seen from the canal, although it is no longer possible to approach the mouth of the tunnel in a boat.
In recent times, water entering the canal from the Brindley tunnel has been blamed for much of the prominent iron ore (responsible for the rusty colour of the water) in the canal, and there are proposals to install filtering (possibly using reed beds) at the northern portal.
In the late 20th Century, the Telford tunnel also began to suffer subsidence, and was closed between 1973 and 1977. The towpath, long disused, was removed, allowing boats to take advantage of the greater draft in the centre of the tunnel.
A series of smaller canal tunnels are joined to the Telford tunnel. These tunnels connected to coal mines at Golden Hill and allowed both the drainage of the mines and the export of coal directly from the mines to the canal tunnel without the necessity of first hauling it to the surface. Small boats of ten tons capacity were used in this endeavour.
The Construction of the Second Tunnel[1]
In 1822, the Grand Trunk (Trent and Mersey) Canal Company having come to the determination to form a new tunnel through Harecastle Hill, near Congleton, Cheshire, Mr. Telford was, at the suggestion of their Engineer, who felt unwilling to take upon himself the sole responsibility, called in to examine and to report upon the practicability of making a second tunnel. This navigation, including the original tunnel, was constructed by the celebrated James Brindley, but the tunnel was of such limited dimensions, as to be quite unfitted for the traffic which had been developed.
Mr. Telford having reported that it was both practicable and desirable to make a larger tunnel, was, after a delay of two years, authorised to make the necessary arrangements. He then recommended that Mr. James Potter, whom he described as 'an active, intelligent young man,' should be appointed Resident Engineer.
The works were commenced immediately, and the tunnel was completed within three years after the commencement of the operations. It was built parallel to the former tunnel, at a distance of 26 yards, and was 2,926 yards in length, 16 feet in height, and 14 feet in breadth.
After it had been worked for two years, Mr. Telford made a minute examination of the tunnel, and found that every part was quite perfect. In a subsequent report to the committee, he stated, 'I did not observe one crack, or fissure, or even one decayed brick, which, in a work of such magnitude and difficulty, performed in the short period of three years, is, I venture to believe, without parallel. Although the materials are thus excellent, and every facility was afforded, I consider it just to state the merit which is due to the Resident Engineer, Mr. James Potter, for the accuracy with which he set out the line, and his unceasing attention and perseverance in providing materials and conducting the works.' Again Mr. Telford, alluding to the tunnel in a private correspondence, says, 'I congratulate you on your successful exertions upon those difficult works, which are the most perfect of their kind, and which do you much honour.'
See Also
Sources of Information
- ↑ Extract from obituary of James Potter
- [1] Wikipedia