The Stillwater–Ngākawau line (SNL), formerly the Stillwater–Westport line (SWL) and the Ngakawau branch, is a secondary main line, part of New Zealand's national rail network. It runs between Stillwater and Ngakawau via Westport on the West Coast of the South Island. It was one of the longest construction projects in New Zealand's history, with its first section, at the south end, opened in , and the beginnings of the Ngākawau Branch, at its Westport end, in 1875. The full line was completed in . The only slower railway projects were Palmerston North to Gisborne, 1872 to 1942, and the Main North Line to Picton, 1872 to 1945.
The main traffic has always been coal. In 2021 opencast mines along the line produced 1,321,541 tonnes of coal, 984,951 tonnes of it from Stockton Mine at Ngākawau. All the other mines in the country produced only 1,234,560 tonnes.
Passenger journeys peaked at around 500 a day in 1946 and ceased in 1967. From 1891 until about 1970 the line had a refreshment room, initially at Totara Flat, then Ikamatua, then Stillwater.
Construction
A railway link from Greymouth east to Brunner was opened in 1876, but work on a link from this point to Westport became delayed for ten years by disputes over the best route to link the West Coast with Nelson and Canterbury. A route for a railway was first proposed by the Nelson Province Engineer, John Blackett, in 1863. As this 1886 map shows, when the extension started, it was intended to be part of a much larger network, which would have linked to Blenheim, as well as Nelson. The distance from Westport to Blenheim, via a summit at Tophouse, was surveyed as and to Nelson , with the longest tunnel being , opposite Lyell. Ultimately, the New Zealand Midland Railway Company (NZMRC) was formed to construct the route, and in 1886, work recommenced. The junction of the route to Westport and the Midland Line to Canterbury was established just east of Brunner in Stillwater, and the NZMRC put most of its energy into the first portion of the SWL from Stillwater to Reefton. This was due to the comparatively easier terrain faced by the route in the valley of the Grey River, and in 1889, the line was opened to Ngahere. On 29 February 1892, the NZMRC opened the line all the way to the south bank of the Inangahua River, directly opposite Reefton, and with the Stillwater–Reefton portion complete in their view, they redirected their energy to the Midland route from Stillwater to Otira.
In the mid-1890s the NZMRC ran out of funds and, after a dispute in the courts, was taken over by the central government. Work on the SWL recommenced in the 20th century, with the Inangahua River bridged, the present-day Reefton station established, and a further section to Cronadun opened in 1908. At the Westport end, construction also commenced, with a 9 km line opened in 1912 from Westport to Te Kuha at the western end of the Lower Buller Gorge. In 1914, the line from Cronadun reached Inangahua Junction, where the NZMRC intended its lines to Westport and Nelson to diverge (in fact, Inangahua remained the probable site for a junction until all work on the Nelson Section ceased in 1931). Work was slowed after the Reform Government took over in 1912. However, the outbreak of World War I brought a halt to construction with only the section through the Buller Gorge to complete. In 1921 the slow progress of the line was being criticised and there was speculation that a route to Nelson might follow the Gowan valley.
The Railways Board reported in 1931 that the line would earn far less than the interest charges for its construction. The Buller Gorge posed many difficulties for construction, but most of the formation and 2 of the remaining 12 bridges had been built, when Parliament voted 40:22 on 8 October 1931 to back the Railways Board proposal to stop work on the Westport-Inangahua line as well. The Labour leader, Harry Holland, suggested, "the influence of the oil interests against the national railways". Some of the workers were transferred to road building. Only after the 1935 election brought about a change in government was there a serious push to complete the line (as well as the similarly postponed Main North Line). Work was formally restarted on 16 July 1936 with a first sod ceremony. The outbreak of World War II created further delays on construction, but this time, work continued through wartime, including electric signalling, a turntable at Westport and easing of grades at Omoto, Jacksons and Stillwater. The "last spike" ceremony was on 2 December 1941. The Public Works Department (PWD) was in charge of construction and were able to operate trains the length of the line by July 1942, but ownership of the route was not transferred to the New Zealand Railways Department (NZR) until 5 December 1943.
The through the Gorge cost £1,231,636 to 1941, with about another £40,000 spent before opening. 360 were employed on the line when work was stopped in October 1931. By the end of 1932 it was 32. Labour MP, Bob Semple, called stopping the works and throwing wheelbarrows, tools, and shovels in the river, a criminal offence. When the Labour Government resumed construction in July 1936, 66 were employed, peaking at 399 in January 1937, none of whom died at work.
Operation
Before the line was completed, mixed trains operated on sections open for service. During the 1917 coal strike, trains between Inangahua and Reefton were suspended. By 1927 one report said that part of the line had lost most of its passengers to motor vehicles. When Inangahua first appeared in the annual reports, 3 years later, it only sold 300 tickets in the year. In 1926 the Minister said local services between Greymouth and Inangahua had been speeded up in keeping with the course followed on the main lines. Between August 1936 and August 1938 a daily morning railcar service was provided from Hokitika on the Ross Branch to Reefton and return by a diminutive Midland railcar. Once the line was completed Vulcan railcars operated from Westport to Stillwater, where they connected with services to Christchurch, and a local service ran between Greymouth and Reefton. From 7 September 1942 there were two railcars each way between Greymouth and Westport, taking 3hr 28min from Greymouth. It was seen as a means of saving rubber and petrol during wartime. The poor roads in the region meant there was more demand for a passenger service than on many other rural routes in New Zealand that lost their passenger services by 1940, but road upgrades led to increasing competition from the private car and all passenger services on the line ceased in 1967, due to the deteriorating mechanical condition of the railcars.
Commodities such as coal, timber, and cement have been the mainstay of freight on the line, and in the 1950s, when coal was still shipped from Westport and Greymouth, the occasional closure of one port meant every operational locomotive on the West Coast was pushed into duty to haul coal up or down the SWL to the other port. Today, the coal traffic still exists in substantial quantities, but it is no longer shipped from West Coast ports; it is carried by train to the deep harbour in Lyttelton on the east coast. A 2017 report said the Stockton Mine is the main source of traffic and that, "if production were to drop significantly, the economic viability of the whole rail network west of Canterbury would be questionable." In 2019 there were 4 coal trains a day of 30 wagons, loading up to 72 tonnes gross and carrying up to 1,460t of coal per train. The Ngākawau-Lyttelton journey takes about 12½ hours for the .
When the line was completed, UC class steam locomotives were utilised on the line, with the B and BA classes introduced in 1957. This was the last mainline duty performed by the B and BA locomotives, and as bridges on the SWL were strengthened, they were displaced in the 1960s by the heavier A and AB classes. In 1969, the SWL became one of the last lines in New Zealand to be dieselised, with the DJ class introduced. DJs were used in 1968, when the line was closed for over 3 weeks by the Inangahua Earthquake and which also caused a derailment. The quake damaged about of the line. In the 1980s, DC locomotives were also placed into service on the line.
One notable feature was the necessity to bank heavy trains heading south from Reefton to Stillwater due to the difficult uphill grade. This was a common feature during the era of steam locomotives, and although banking was dispensed with on most lines when the conversion to diesel-electric motive power was made, the SWL was initially an exception. Some trains had two DJ class locomotives at each end, but this practice has now come to an end, with trains usually formed and loaded in such a way that banking is unnecessary. Trains on the line are regulated by track warrants.
Slips
Slips have been a continuing problem in the Buller Gorge, due to steep slopes and high rainfall. During construction, broom was planted to stabilise slopes. Slips blocked the line in the Gorge in 1944, 1961, 1966 (Rahui), 1979 and 2010 In 1945 a train near Cascade was derailed by a slip, in 1949 one hit a slip and another was derailed by a stone, then in 1950 a railcar hit a slip, in 1955 a slip near Rahui derailed another and a goods train was damaged in 1960 between Cascade and Te Kuha. On 30 November 1979 a westbound locomotive was derailed by a slip near Cascade. On 3 January 2002 a train was derailed by a slip just over 3km west of Rahui. On 13 January 2011, between Rahui and Tiroroa, 5 wagons derailed due to a slip and 3 months later a slip punctured a fuel tank near Te Kuha. The south portal of Tunnel 3 was blocked by a slip, which an empty coal train ran into on 16 October 2023. The line reopened on 27 November.
A 2012 study of the problem listed another dozen slips between 2004 and 2011. With a maximum speed in the Gorge, due to curvature, there have been no serious injuries and limits are between Te Kuha and Cascade, at the worst spot, and below the limestone cliffs of Whitecliffs, where KiwiRail monitors metal pins across the limestone to check it remains stable, just west of Buller. The line is also inspected if rainfall exceeds .
As mobile phone coverage in the Gorge is poor, 'Compulsory Call Location' boards are at Mackley, Berlin, Tiroroa, Cascade and Te Kuha, instructing drivers to phone Train Control to monitor the progress of trains in case of a crash.
Stations Stations and sidings on the southern section of the line (those north of Westport are listed in the Seddonville Branch article) – NB the opening and closing dates in columns 3 and 4 sometimes vary from those in the notes, which are derived from different sources. Station NameDistance from GreymouthOpenedClosedHeight above sea levelNotesStillwater14 November 1887The line from Brunner via Stillwater to Ngahere opened for passengers and goods on Thursday 1 August 1889. Stillwater was the junction with the Midland Line from 15 November 1887, when that eastward route was available to Kokiri, though, apart from a few excursions, trains didn't run until 13 March 1894. The station had a small NZR refreshment room from 8 January 1927 to 15 March 1962 (taken over on lease till at least 1970) and a Post Office from 26 September 1906 to 30 June 1976. There was a fire at the station on 4 August 1960. The TranzAlpine called until 23 September 1999, after which Brunner was substituted as a stop. A platform, 8 tracks and a shed remain, with a sawmill next to the station, which has a siding able to take 17 wagons.