Kapiti Line

Construction

The Kapiti Line was constructed by the Wellington and Manawatu Railway Company as part of its line between Wellington and Longburn, south of Palmerston North. It was built by a group of Wellington businessmen frustrated with the indecision of the government about the construction of a west coast route out of Wellington. Construction of the line began in September 1882 and followed a circuitous, steep route via Johnsonville. It was opened to Plimmerton in October 1885, and on 3 November 1886 the line was finished, with the final spike driven just north of Paraparaumu, at Otaihanga.

On 7 December 1908 the government acquired the Wellington and Manawatu Railway Company, and incorporated it into its national network as the southern portion of the North Island Main Trunk line.

Deviation and electrification

In 1928, work began on a deviation to avoid the difficult Johnsonville section of the line. This deviation had two significant tunnels between Kaiwharawhara and Tawa. It opened to freight on 24 July 1935 and to passengers on 19 June 1937. The Johnsonville section was retained as the Johnsonville Line.

The line from Wellington to Paekakariki was electrified from 24 July 1940, primarily to avoid smoke nuisance in the new deviation's lengthy second tunnel, and to provide extra tractive effort on the Paekakariki Hill between Pukerua Bay and Paekakariki. Paekakariki was thus established as a major station where trains swapped from steam (later diesel) to electric motive power, and it was the northern terminus of the commuter line for many years. Electrification was extended to Paraparaumu on 7 May 1983 and to Waikanae on 20 February 2011.

Duplication

The Manawatu Railway Company railway when first constructed was a single track railway with crossing loops at principal stations to allow opposing trains to pass. In the 1920s the need for extra train services on the line was recognised, both to increase the tonnage of goods trains and to allow more frequent suburban passenger services. To increase the number of trains that the line could carry, duplication and electrification of the line along with other improvements, such as curve easements, was planned and progressed in stages.

The first section of track duplicated was the Tawa Flat deviation. Completed in 1935, it provided double track from Wellington to Tawa Flat.

The section from Plimmerton to South Junction (a little north of Muri Station at the top of the Paekakariki Hill) and from North Junction (at the northern portal of northern Paekakariki tunnel) to Paekakariki was completed in 1940. The difficult single track section between South and North Junctions that passed through five short single track tunnels was left as single track. A proposal that the tunnels on the section between South and North Junctions be replaced with a single double track tunnel has been considered but has not so far been approved.

As part of the Plimmerton to Paekakariki duplication, rather than install signal boxes at North and South junctions, as had been previous practice, a three-wire remote control system was installed so that the signalling of trains at the junctions could be directly controlled from the Train Control office in Wellington. This was the first Centralised Train Control (CTC) system to be installed in New Zealand and the first outside the United States of America.

Further duplication was delayed in the 1940s but continued in the 1950s with the completion of the Tawa to Porirua section on 15 December 1957.

Double track from Porirua to Mana was opened on 7 November 1960. Harbour reclamation allowed mostly straight track with the line no longer following the curves of the shoreline bays north of Porirua. A new station and bridge at Paremata were required. The Mana to Plimmerton section was opened on 16 October 1961.

In conjunction with the extension of electrification to Paraparaumu in March 1983, double track was extended from Paekakariki to McKays Crossing. The section between McKays Crossing and Paraparaumu, built across a peat swamp, remained single track. Extension of double track from McKays Crossing to a junction south of the Waikanae River bridge was completed in February 2011 to coincide with the extension of electrification to Waikanae.

Operation

From electrification until the 1980s, the majority of commuter services on the line were operated by DM/D electric multiple units, with some carriage trains hauled by ED and EW electric locomotives, particularly at peak periods. ED and EW locomotives also hauled freight trains over this section until the tunnels between Pukerua Bay and Paekakariki were lowered in 1967 and DA diesel locomotives could be used into Wellington.

From 1982 the new EM/ET electric multiple units were delivered. They had been ordered to replace the wooden carriage trains hauled by electric locomotives on commuter services and largely displaced the DM/D units on the Paraparaumu Line.

By the 1980s, the ED and EW electric locomotives were not required for either freight trains or for commuter trains. They were retired due to age and lack of use, the EDs by 1981 and the EWs by 1988. From 2010 the introduction of the Matangi EMUs provided extra passenger capacity, and enabled the remaining DM/D EMUs to be withdrawn in 2012.

A proposal to extend the electrification to Waikanae was approved by the Greater Wellington Regional Council on 8 May 2007. This project included the double tracking of the single track line between MacKays Crossing (between Paekakariki and Paraparaumu) as far as the rail underbridge and river bridge south of Waikanae. The $90 million project started in December 2008, and was completed in 2011, with the first commuter trains to Waikanae on 20 February. Completion of the project was delayed to 2011 to minimise commuter disruption by working in the quiet end-of-year holiday period, according to ONTRACK program director David Gordon. The project involved 50 workers and 20 machines installing 600 traction poles in eight or nine metre deep holes, and laying 30 km of rail and 30,000 sleepers. The project allows commuter services from Waikanae every 15 minutes at peak travel times but more commonly every 30 minutes. The new Matangi electric multiple units were used on the Kapiti Line from mid-2011. Paraparaumu and Waikanae stations were upgraded at a cost of more than $1 million each. Upgrading Waikanae station rather than moving it south of Elizabeth Street or providing a road underpass has been criticised locally, as frequent closing of the Elizabeth Street level crossing south of the station may increase traffic congestion in Waikanae.

Ten traction substations along the line take electricity from Wellington Electricity or Electra's 11,000-volt distribution network and transform and rectify it to 1500-volt direct current for the overhead traction lines. The substations are located at Wellington, Kaiwharawhara, Glenside, Paremata, Mana, Pukerua Bay, Paekakariki, Raumati, Lindale and Waikanae. Also along the line are two "cross-tie" substations at Ngauranga and Tawa, which provide a switching function but don't have transformers or rectifiers.

The future

Proposals for new stations at Raumati, between MacKays Crossing and Paraparaumu, and Lindale, north of Paraparaumu near Otaihanga, were on hold, to be reconsidered after 2010, as it was claimed that there were problems affecting a station at Raumati (the provision of access to SH 1 and park-and-ride facilities) and an unstable hillside behind the line.

The 2013 Review and Draft 2014 Review of the Wellington Regional Public Transport Plan confirmed that building additional stations on the Kapiti Line at Raumati and Lindale was no longer recommended, with the cost of new stations outweighing the benefits. The detailed analysis for Raumati (which was a "viability benchmark" for other new stations) said that said that the modelled peak-hour patronage needed to be about 300 new passengers to justify a new station, and that most Raumati users would have switched from Paraparaumu Station. Network extensions beyond the current Metlink rail operation limits would be by "shuttles or non-electrified services" running to Wellington.

Further extension of the electrification 15 km north from Waikanae to Otaki remains a possibility. A group known as "Save Kapiti" is actively campaigning for the extension. The Otaki Community Board also supports the extension of electrification. Provision has been made during road earthworks north of Waikanae for a future crossing loop between Peka Peka and Otaki. In 2012 the Greater Wellington Regional Council investigated extension of the electrification with Matangi trains north of Waikanae to Otaki (estimated cost $30 million for the Otaki project) and north of Upper Hutt to a new station at Timberlea. In March 2014 the GWRC said that electrification to Otaki was estimated to cost $115 million to $135 million and was too costly for the number of new passengers it would attract (approximately 250 new passengers). Because the trip would take over an hour, new trains with toilets would be required. As an alternative to electrification, it was suggested that diesel multiple units could be used on services north of Waikanae. This could be a "final nail in the coffin" for the under threat Capital Connection service from Wellington to Palmerston North, which also stops at Otaki.

The section between Pukerua Bay and Paekakariki may also be double tracked or replaced by a less steep deviation during the first half of the 21st century, although the present proposal is to daylight only the northernmost (No. 7) tunnel which is through rock, and have double track north from there.