Evans Bay is the site of the first Patent Slip in Wellington and indeed New Zealand. The Patent Slip, consisting of two slipways built in 1873 and 1922 respectively, was designed to accommodate large ships over land for maintenance and repairs and is considered a great engineering feat.

Enthused by an increase of ships into Wellington in the 1860s, the Provincial Superintendent, Isaac Featherston, proposed a new floating dock or patent slip be constructed to accommodate vessels of 1,200 tons. The Wellington Provincial Council formed an investigative committee, who reported a patent slip was the best option, that it was practicable to build one, and ‘..should be done without any necessary delay’. In response to the report, legislation was passed allowing the acquisition of land for a slip.

The first contract awarded failed and was subsequently awarded to a British firm, Kennard Bros, in 1866. All necessary equipment and materials were shipped from England and unloaded at Evans Bay ready for construction. However, a number of issues arose between Kennards and the Council and work stalled for five years. In 1871, the newly formed Wellington Patent Slip Company took over what Kennards had abandoned, and the slip was inaugurated on 2 May 1873.

The Evans Bay Patent Slip was a great engineering feat. Although construction above the high tide mark was reasonably straightforward, work underwater was far more difficult, requiring accurate work by divers who could only work in optimal conditions. A 500 foot (154.2 metre) jetty was also erected improving the communication with ships. Shortly after opening, J. Rees George, an engineer and manager of the Patent Slip explained how a 200-ton, 180 foot (54.9 metres) long cradle ran on wheels along a set of ‘ways’ or tracks. Two chains were used; a larger 62-ton chain for hauling vessels and a smaller 8 ton chain for lowering vessels off the slipway. The chains worked on a seven-cogwheel winch which was powered by two 25-horse power steam engines. There were a number of buildings in addition to the winch houses and boiler rooms associated with the slipways, including dwellings, a store, inspector’s office and carpenter’s shop to the west of the slipways, and a messroom and blacksmith’s shop to the east.

In 1908, agreement was reached between the Wellington Patent Slip Company and the Wellington Harbour Board. The Patent Slip Company would retain possession of the facility for 25 years in collaboration with the Union Steam Ship Company, a majority shareholder. A condition of the agreement was that improvements were made, and following further reclamation of land a 61-metre long wharf was erected in 1912. In 1913, plans began for a second slip, but this smaller but steeper 750-foot (228.6 metre) slipway alongside the first was not completed until December 1922.

In 1961, the Union Steam Ship Company did not renew its lease and ownership of the patent slip returned to the Harbour Board. In 1969, the first slipway closed and an upgrade of the second slipway commenced. The No. 1 slipway was sold for scrap in 1972 and the machinery removed. The No. 2 slip continued to operate until 1985, when it too closed. The No. 2 slip winch was purchased and removed by a Dunedin slip company in 1982, and is still in use today. The cradle was dismantled and removed with some parts being used for the ‘City to Sea’ bridge.

Following the demolition and removal of the slips and associated buildings, the land was then drastically altered. During the 1980s much of the valley at the head of the No. 1 slipway was filled and landscaped, covering any remains of the No. 1 winding house. Some visible features remain above ground, including four piles from the No. 1 wharf and sections of chimney from the No. 1 slip boiler house, as well as the No. 2 slip’s rail system, jetty, and some evidence of the brick engine room.

In 1990 the Wellington City Council (WCC) acquired the majority of the site, subsequently subdividing and rezoning it. In 2003, WCC applied to re-zone the site once more. The Maritime Archaeological Association of New Zealand (MAANZ) was one of the main advocates for zoning it as a heritage area and fought for the boundary to be widened to include the No. 1 slipway. After consultation the boundaries were expanded, and in 2006 a new interpreted heritage area was unveiled.

In 2002-2003, MAANZ also initiated two archaeological surveys. Divers drew detailed underwater surveys, while a geophysical survey and non-invasive digs identified a number of underground features, the most significant being the possible discovery of a baseplate from the former No. 1 engine house.

The Evans Bay Patent Slip is a site of great historical and technological significance, locally, nationally and internationally. The seven cogwheel winch built by Kennards is possibly the only one ever produced, and rated for a pull of 2000 tons it is also the largest of any winch of its time, making it extremely rare. In addition to the large machinery, a Patent Slip of this size is exceptional; from the 1870s it was common to maintain large ships by dry-docking. A number of engineers have identified the construction of such a large slip facility, from scratch, with primitive machinery and in such a difficult location as being an outstanding engineering feat. In addition, it is undoubtedly the first large scale underwater construction in New Zealand.