Construction

During much of the 1800s, the rich coal deposits of the Rhondda were important to the local economy.^[2] By the 1870s, the volume of coal being extracted threatened to exceed the capacities of the Taff Vale and Cardiff Docks Railways. A typical return journey that took two days because of congestion and inadequate handling was a hindrance to customers, particularly the coal shipping facilities at Swansea. There was a demand for another railway line to relieve the situation. The Rhondda & Swansea Bay Railway (R&SBR) was incorporated on 10 August 1882. It established a shorter route to Swansea via the Afan Valley passing through the 1,700-foot-high (520 m) Mynydd Blaengwyfni.^[2]

Sydney William Yockney was employed to engineer the route. He had connections to tunnel engineering through his father, Samuel Hansard Yockney, who was engineer for the construction of Box Tunnel on the Great Western Railway and worked for Isambard Kingdom Brunel on other tunnel projects.^[2] The contract for the section of line that included the Rhondda Tunnel was awarded to Neath-based contractor William Jones and William Sutcliffe Marsh was the resident engineer. As of 2016, the Rhondda Tunnel is the second longest in Wales at 3,443 yards (3,148 m).^[2]

On 30 May 1885, the ground was broken for the tunnel which was expected to be completed in three years. Progress was hindered by land purchase at the eastern end of the line that took 15 months to resolve. Early reports by Yockney to the R&SBR's directors were positive, ground conditions were favourable and there was little water ingress. The tunnellers who worked from shafts driven into either end of the approach cuttings were equipped with compressed air-powered rock drills and were boring into the sandstone at 240 yards (220 m) per month. Because of the tunnel's depth, in excess of 900 feet (270 m), intermediate shafts to speed construction were discounted.^[2]

The tunnellers faced dire conditions, resulting in injuries and deaths, several due to rock falls and explosions. By 1887, the tunnelling had slowed to 70 yards (64 m) per month which was attributed to a shortage of men and underground springs. The completion date was moved to 31 July 1889. The headings met on 16 March 1889 and were perfectly aligned, but the delays led to William Jones being stripped of the contract in favour of Westminster-based Lucas and Aird in September 1889.^[2]

The new contractor brought 1,600 men on site and 300 more houses were built at the Rhondda side. Electric lighting was installed in the tunnel and progress was restored. On 2 May 1890, the Rhondda Tunnel was inspected by Colonel Rich of the Board of Trade. He said the tunnel should have been fully lined and would not authorise its use for passenger traffic until it was done. The contractors installed 759 yards (694 m) of brick arch above the arched concrete sidewalls which took less than 54 days because Lucas and Aird had anticipated such a requirement.^[2]

Operation

On 2 July 1890, the Rhondda Tunnel was opened. The R&SBR had failed to purchase adjacent coal seams above and below the tunnel which was common practice to prevent other parties from mining and damaging the tunnel. Within decades the seams were exploited and the tunnel began to distort.^[2]

Between 1938 and 1953, around 500 steel ribs were installed to resist pressure which was causing inward movement of the side walls and pushing-up of the crown particularly towards eastern end. It did not solve the problem and a settlement of 15 inches (38 cm) was recorded over a 12-year period. More problems were caused by substantial water penetration from underground springs which weakened and washed out the mortar between bricks in places. Several lengths of arch were relined when sections of brickwork became loose and fell onto the track. Speed restrictions were imposed to guard against the threat posed by a collision with debris.^[2]

A survey in 1967 revealed severe distortion around the middle of the tunnel close to a geological fault.^[2] The rate of deterioration was so severe that the inspector closed the tunnel to traffic on safety grounds. On 26 February 1968, it was closed as a temporary measure, whilst a decision was made on the future of the line.^[2]

In December 1970, the Ministry of Transport announced the withdrawal of passenger services via the tunnel, citing a decline in usage and the provision of a bus service. The ministry deemed the estimated cost of repair at £90,000 was prohibitive. This conveniently coincided with the Beeching cuts and stations either side of the tunnel, (Blaenrhondda and Blaengwynfi), were closed at the same time. Following a decade of disuse, in 1980, both portals were covered over and landscaped to prevent unauthorised intrusions, which had become commonplace since its closure.^[2]