In 1880, William Frank Oakes won a tender to construct a race between the old dam and a pipeline connection near what is now Richard Prouse Park and Reservoir Road. The tender was awarded in June 1880 at a cost of £233 15s, but the specific work it covered remains unclear. Oakes later secured another contract for race work valued at £7,439 7s 6d on July 1881 which is regarded as the date when construction began. Other reports state as much as £15,000 being awarded for the total work. This marked a significant step in the development of Wainuiomata’s early water supply infrastructure.
The race was designed as a concrete covered race / culvert measuring 96 chains (1,920 metres) in length, 4 feet in width, and 2 feet 9 inches in height from the crown of the arch to the bottom of the invert. A concrete mixing machine was installed at the dam site to facilitate the construction process.
Engineering and Transporting Materials
The concrete used for the race and reservoir was mixed on-site using a machine under the direct supervision of the City Engineer. This machine featured an iron cylinder with a capacity of 100 cubic feet and was powered by the engine previously used in the steam launch “Perfect Cure”. Once mixed, the concrete was quickly transported down the Sinclair Tramway to required locations.
In addition to old newspaper records documenting this endeavour, numerous old tracks still run from Reservoir Road (the location of Sinclair Tramway) to Maintenance Road above, which ran parallel. The race was primarily situated between the tramway and this unsealed road / track above.
Construction of Colemans Tunnel
Coleman’s Tunnel was built around 1882 as part of the water race project. While the race including the tunnel was tendered and constructed by William Frank Oakes, its interior was lined with bricks by John Coleman, after whom the tunnel was named. The tunnel’s function was to collect water from the race at a pressure well, where it entered the tunnel and was then directed into the main pipeline to Wellington.
Problems with the Water Race
As early as 1887, Wellington’s city surveyor suggested replacing the water race and pressure well with cast iron pipes, estimating the cost at £7,000 due to large leaks. However, others argued that repairing the water race would be far cheaper by lining its sides and bottom with T. & G. totara timber. They also claimed that poor maintenance was the main issue and that if the manhole covers had been periodically removed to allow inspection of the race, only minimal repairs would have been needed. Despite its intended purpose, the tunnel and race were found to be inefficient due to excessive leaking with a further problem of bywash / overflow at the tunnel which required turning the water flow on and off to regulate. The leaks were more about neglect than defect, according to some reports though.
It was later realised that if the pipes had been laid 10 feet lower to the reservoir, there would have been no need to periodically shut off Wainuiomata’s water supply to prevent the well from overflowing. The natural river flow, combined with the additional reservoir storage, would have been sufficient to meet demand, while maintaining consistent water pressure. Installing lower pipes would also have been more cost-effective than constructing the race and well.
By 1899, both the water race and Coleman’s Tunnel had been abandoned and replaced by a pipeline from the Lower Reservoir Dam. This new pipeline connected to the cast-iron pipe that crossed the Wainuiomata River and continued for 3.5 miles (5.6 km).
Legacy of the Early Wainuiomata Waterworks
Although the water race and tunnel/well were abandoned early on, both still remain today. Over time, modern pipelines and treatment plants have replaced this and other early systems, but their legacy remains an important part of Wainuiomata’s water supply history.
