Photo Source: © Jeremy Foster
The 30 inch pipeline carried water from Wainuiomata to Wellington and formed a key part of the city’s early bulk water supply system. It originally began near Whitcher Grove, just west of Coleman’s Tunnel, where a two kilometre water race conveyed water from Lower Dam before feeding into the pipeline.
In 1902 the water race was decommissioned and replaced with a new section of 30 inch pipe running along the lower side of Reservoir Road for a distance of 100 chains, or about two kilometres. At the same time a Venturi meter was installed to measure the flow of water entering the main. The intake was positioned within the reservoir at a depth of 9 ft 6 in, rather than the 6 ft depth used by the earlier water race, allowing water to be drawn from a deeper and more stable level. In 1911, when Morton Dam was completed, a second 30 inch pipeline was constructed to connect the new reservoir to the same 30 inch pipeline.
From there the pipeline passed through two major tunnels, Dick’s Tunnel and the Waiwhetu Tunnel, which carried the main through the hills to Gracefield. The line then continued along the Petone Esplanade and Hutt Road to the Thorndon pumping and reservoir area near Thorndon Quay. From this point water was distributed to several of Wellington’s inner city service reservoirs, supplying the growing city in the early twentieth century.
From the mid 1980s the system began to change significantly as Wellington’s regional water supply network expanded. Around 1986 the 30 inch pipeline started to be progressively supplemented and replaced by the Green Pipeline, a much larger trunk main running through the Hutt Valley. This modern pipeline forms part of the metropolitan bulk water system operated today, allowing water from multiple sources including Wainuiomata, the Hutt River and other catchments to be distributed across the wider Wellington region.
As a result the Wainuiomata supply is now integrated into the regional bulk water network, which feeds numerous reservoirs across Wellington. Water originating from the Wainuiomata catchment can ultimately reach reservoirs supplying suburbs such as Karori, Brooklyn, Kelburn and other western areas of the city.
Although much of the original trunk route has been superseded, sections of the historic 30 inch pipeline remain in use today as part of the wider network. Portions of the 30 inch main, particularly along Reservoir Road in Wainuiomata, continue to operate within the modern system.
