Tales from Harecastle Tunnel

My childhood introduction to canal tunnels centred on Harecastle, one of the nation’s longest, which provides a subterranean north-south connection between the plains of Cheshire and the Potteries.

Our early underground adventures took place in the late 1960s, at which time the tunnel’s roof lining bulged down in several places, and the remains of a raised towpath projected ominously from its corrosive, ochre-coloured waters. In those days most hire-boats were made from flimsy plywood. Ours was a Dawncraft cruiser with a centre cockpit, which came complete with a supposedly collapsible windshield. When we had gone into the tunnel far beyond the point of no return, we discovered that the collapsible windscreen had been fixed in the ‘up’ position following an earlier accident, and the end result was, as Spacex would describe it, a sudden and unscheduled disassembly.

I have always been intrigued by Harecastle Tunnel, with the dark portals of its abandoned twin sitting just to the west. Indeed, it only took a few photos of boats entering the old Brindley Tunnel at the turn of the 20th century, and a few more of its unusual electrical tugs, to lure me down yet another rabbit hole of canal history. This time the hole in question was to prove very long and very deep.

History of the tunnels

Navigating through Harecastle Hill has, it seems, always been a somewhat problematic endeavour. The original route was conceived by James Brindley but his death in 1772 meant that he never saw the tunnel completed, and this task fell to his brother-in-law, Hugh Henshall. Henshall supervised the remaining construction and witnessed its opening to traffic in 1774, two years before the entire Trent & Mersey Canal route was completed.

The Brindley/Henshall tunnel quickly became a victim of the canal’s success. Because it was low and narrow, legging through was a slow business, taking up to four hours. This meant that boats often faced lengthy delays and the site became a severe bottleneck. Reassured by the growing levels of demand for canal transport, Thomas Telford was later engaged to engineer a new and larger tunnel which would run parallel to the old. By driving cross-connections between old and new tunnels, work progressed quickly, consuming 8.8m bricks. Within three years the new £112,681 (£10m in today’s money) line was complete, culminating in an opening ceremony held on 16th March 1827.

Telford’s new tunnel included an elevated towpath which meant that, for northbound traffic, craft could be drawn through in less than an hour and a half, although the southbound traffic was still obliged to use the old, smaller tunnel. Because the tunnels were to some extent interconnected, water was able to move between them as boats headed through, easing their passage.

In spite of the engineering advances applied to its construction, Telford’s ‘new’ tunnel suffered its share of subsidence issues, and a 1907 survey reported that water was flowing over the towpath for 400 yards. Subsidence continued and by 1910 these lengths were 13in underwater. This movement was attributed to the fact that the tunnel was driven through 50 separate seams of coal, which dropped to the south, interspersed with layers of mudstones, shales and sandstones. Water found its way along these strata, creating voids behind the tunnel wall which undermined its integrity.

The first tunnel tugs

With the towpath virtually unusable and high volumes of boats wishing to pass through, consideration was given to the use of a steam-tug system which had been successfully employed elsewhere. Unfortunately, this option was not possible at Harecastle because, while both tunnels had been built using 15 vertical construction shafts, these had not been retained for ventilation and any attempt to use steam would have almost certainly led to the asphyxiation of boat crews.

Twenty years after the new tunnel’s completion, the Trent & Mersey Canal Co was bought by the North Stafford Railway, which took the unusual step of promoting its newly acquired canal.

NSR was pioneering in its application of electrical technology and, within its 1904 enabling Act of Parliament, it gained specific approval to both remove the towpath and to use electricity to propel tug boats through Harecastle Hill “using electricity or mechanical power other than steam”. However, it took until 30th November 1914 for these plans to be put into action.

In anticipation of the introduction of electric tugs, the tunnel was dredged in 1913, removing 948 tons of sediment from the base. This was followed by the construction of the Chatterley Power House at the southern portal, which contained the generators used to charge the accumulator barges that would power the tugs.

The electric tugs were used in the Telford tunnel, pulling themselves along a 3,500-yard fixed steel rope which had a 5/8in diameter and a 2in circumference. This cable was laid on the tunnel bed (hence the dredging) and anchored at both ends, with a tensioner sited at the southern end. This rope passed over two 5ft-diameter wheels on the tug, each of which was driven by a 15hp motor. There was no steering mechanism and the tugs just followed the cable, trailing first an accumulator boat and then a string of narrowboats. A major downside to this submerged cable approach was wear and tear, as it needed to be replaced every nine to 12 months.

The first 40ft tug was built in 1914 with a draught of 3ft and cost £1,563. Seventeen years later a second tug was introduced to provide cover when the original was being repaired.

The accumulator barges

Two 72ft-long accumulator barges were built in the NSR yard, containing 115 chloride cells housed in lead-lined teak boxes. These massive accumulators were recharged over a period of several days at the charging station located between the old and new tunnels’ southern portals. The charging process was slow, involving two 70bhp gas engines turning at 600rpm, which were capable of generating 45kW of power.

In their first year of operation, the tugs were typically moving 100 boats north and south each day, and were made available for 18 hours in every 24. They generally towed strings of around 17 boats, although the design maximum was nearer 30. The resulting train of boats could be up to 400 yards long and moved at between 2mph and 3mph. With improved transit times, the old collapsing Brindley tunnel was abandoned.

While the towpath remained in place through Telford’s tunnel, all boats were expected to make use of the tug service. The old towpath gradually deteriorated and was finally removed to let craft take a more central line and so gain a little more headroom.

Overhead power supply adopted

In 1931, NSR was taken over by the Midland & Scottish Railway which brought some new ideas for the canal. The accumulator-barge system had proved costly to maintain as the batteries degraded, and it was soon abandoned in favour of electrical power, delivered via overhead cables suspended on wooden poles set into the tunnel roof.

Instead of charging the accumulators, the generators at Chatterley had their power routed into the overhead wires, which were connected by the boat travelling under them, using what were variously called current collectors, pick-up poles or trolley poles. In reality these were an adaptation of technology used on trolleybuses, and represented an early version of the pantograph set-up we see on top of modern trains today. Every electrical circuit needs both a positive and a negative and, in this case, it appears that the submerged cable served as the negative.

The new electrical-cable delivery system reduced transit times to around 45 minutes and the orientation of the trolley pole was reversed on the tug for the return journey. One of the most vivid descriptions of this system in operation was written by Tom Rolt during his visit in 1939: “Vivid blue sparks spluttered from the overhead conductor… and from the dark depths ahead a distant muttering slowly grew to a prodigious groaning and grinding sound, like that of a decrepit tram car climbing a steep hill.”

The practice was to charge 6d [2½p] for towing each empty boat or one loaded with less than 2 tons, a fee which increased to 1 shilling [5p] for each loaded boat carrying more than 2 tons. The tickets were issued and checked by a second tunnel employee who saw the craft safely into the tunnel and then ran along the towpath to catch up with a boat towed behind the tug, which served as his ‘office’. Looking at the old photos, the conductor’s boat was probably a repurposed round-bottomed icebreaker.

A period of decline

The years before World War II were very busy, with a never-ending stream of boats passing through the tunnel, and long strings assembled at either end while their horses were led over the hill following the aptly named Boat Horse Road.

With the war over, there was a general decline in canal traffic. Whereas a typical day would have seen over 100 boats moving either way under the hill, in the 1950s this dropped to just 100 boats a week, with the tugs often running empty to maintain their published schedule of eight passages per day. Over time the condition of the tugs and the associated equipment deteriorated to the point that there was no reliable tug service available, and it was not unknown for diesel-powered boats to make their own way through, notwithstanding the lack of ventilation.

In 1954 the nationalised British Transport Executive abandoned the tug service altogether and instead installed the forced-air ventilation system we see today. This involves three 38in-diameter fans located in a purpose-built building at the southern end of the tunnel, which suck the foul air out and make it safe for use by self-propelled craft.

Modern issues

By the time I first encountered Harecastle Tunnel, the overhead electrical gantries were gone and it wasn’t long before the ongoing subsidence made boat passages impossible. Two small falls occurred in July 1973 which were quickly patched but further movement occurred in the September, which forced a long closure for major repairs. In the event, whole lengths of the tunnel had to be rebuilt by three separate contractors, packing the voids and carefully rebuilding the lining foot by foot, achieving about 4ft of repairs each week.

In one collapsed section, the original plans suggested the presence of a construction shaft above, raising fears of a catastrophic collapse onto the workmen below. Excavations were carried out on the surface and eventually a 9ft brick-lined infilled shaft was located and plotted by drilling down to the tunnel 165ft below. This exercise established that the shaft was in fact 17 yards from where it was expected. The risk of shaft collapses prompted British Waterways to locate and drill other sites along the tunnel’s length, where future repair work was considered likely.

All the sections graded ‘bad’ were repaired over a four-year period and the tunnel was reopened to traffic in April 1977. A further 90 yards, which had been graded as ‘poor’, were addressed during winter closures over the following decade and, so far, these remedial works have proved successful.

This account of the Harecastle tunnels barely scratches the surface of their story. As I looked deeper into the history and its unique tunnel tugs, I came across the meticulously researched book, Harecastle’s Canal and Railway Tunnels by Allan C. Baker and Mike G. Fell, which is well worth its £25 price tag. Possibly a good present idea for the canal enthusiast who has everything?

A last look at Brindley’s tunnel

Brindley’s original tunnel continued to operate for nearly 90 years after Thomas Telford’s was completed, but in the end the subsidence occurred faster than repairs could be made, and the old tunnel was closed to traffic in 1918, leaving just an empty portal at each end to stand in silent memory of 150 years of trade.

However, if you leave an open hole in the ground, eventually someone will decide to go in and take a look. The last recorded inspection of the highly unstable Brindley tunnel took place in July 1979 when two adventurous Olympic canoeists, Jon Goodwin and Robin Witter, paddled far into the darkness and returned with a detailed report, plus a collection of unique photographs revealing how it looked at that time.

The following is a precis of their discoveries, which are included as a fascinating 11-page appendix in Harecastle’s Canal and Railway Tunnels.

Goodwin and Witter first entered the northern end at Kidsgrove, slithering over 100 yards of silt to reach water beyond, which was dammed up to around 2ft higher than the adjacent Telford tunnel and initially offered about 6ft of headroom. Along the way, they identified a number of side adits that may connect to the newer canal tunnel but, given the raised water level, they could see no evidence of the interconnecting underwater passages which are believed to exist.

At 675 yards in, a precast concrete pipe enters the tunnel from the west, a modern addition which is part of an overflow system for the nearby Bath Pool Reservoir, built when a new railway tunnel was constructed in the 1960s. At 700 yards, they discovered the tunnel to be completely blocked by sand, which is inconsistent with the local geology. A contemporary report in the Railway Gazette indicates that the railway engineers digging their new tunnel found “two old mine shafts”, one of which they bridged and the other was filled in to provide a stable base for the rail crossing. It is likely that rather than mine shafts, the railway engineers had discovered two construction shafts used to build the canal tunnels.

The intrepid duo then turned their attention to the tunnel’s southern entrance, monitoring their progress into the hill using the old 100-yard markers which remained attached to the eastern wall. At this end, the water was dammed to about 1ft above the adjacent canal level and was heavily ochre stained, with the crown of the arch being about 5ft above water, dropping to 4ft within 200 yards. The mineral ingress had created stalactites, and curtains of mineral deposits were found in an array of white, gold, ochre and crimson stretching right across the tunnel.

At 800 yards, the headroom dropped to about 3ft and the waterline width reduced to 4ft, after which they found a navigable access tunnel, probably leading to the Golden Hill Colliery which branched off to the west. Its arching roof was at the same height as the main canal tunnel but had suffered a collapse 10 yards in, causing the channel beyond to become completely silted up.

The ochre-stained watermarks on the tunnel walls suggested water-level fluctuations of about 18in, and the tunnel height dropped to a mere 3ft at 900 yards. At this point, sight of the southern entrance was lost, the quality of the brickwork deteriorated and the tunnel started to weave.

The local mining activity in this area had caused the tunnel to subside, placing the distance markers underwater. At an estimated 1,100 yards, 20ft of the eastern wall had fallen in, leaving the brickwork hanging precariously, followed by a further fall at 1,200 yards.

At 1,400 yards, the duo reached the midpoint of the tunnel and found an enlarged chamber 80 yards long, with the height increasing from 3ft and a width of 4ft to a relatively cavernous 10ft high and 13ft wide. The purpose of this wide section, midway along the tunnel, is something of a puzzle and may have been a loading area or possibly a passing place.

Beyond the wide section, the main tunnel reverted to its 3ft height, leading to a further 40ft-long fall at 1,600 yards, followed by an area of ironstone stalactites which covered the tunnel roof, reaching down to 2ft 6in above the waterline. From here the tunnel height rises to 5ft at the 1,800-yard marker, the last sign to be seen. The tunnel was explored for a further 400 yards at which point Goodwin and Witter encountered a blockage of sand which was probably the other side of the same blockage they discovered from the northern end.

Somewhat strangely, the pair observed the water in the tunnel rise by over 1ft in an hour, without there being any rain outside. As the water in Brindley’s tunnel is dammed to a level significantly higher than in Telford’s, the change can’t be attributed to boats passing in the adjacent tunnel, and its exact cause remains a mystery.

Goodwin and Witter were at pains to point out the danger inherent in their exploration, with old-fashioned flashbulbs potentially igniting any methane in the tunnel, and any noise possibly triggering further rock falls. They published a brief account of their underground adventures in the Staffordshire Evening Sentinel, after which British Waterways erected a strong steel fence at both ends to prevent any further amateur explorations.

The appendix, on which this summary is based, is beautifully illustrated and in itself justifies the purchase of a copy of Harecastle’s Canal and Railway Tunnels, if any encouragement is needed.