The Exhibition Drive Pipe

The pipe that runs along the Exhibition Drive track may look like a historic relic but, despite being laid in 1912 and in poor condition, most of it is still in use taking all of the water from the Upper Nihotupu dam.

This slideshow requires JavaScript.

The pipe is actually the replacement of an earlier Emergency supply pipe known as the Auxiliary Supply which roughly followed the same route. In the late 1890s Auckland’s water supply was mostly from Western Springs. Quickly increasing usage (partly due to the introduction of flush toilets) meant water severe water shortages for several years. It got to the point where the water was being turned off at night.

NihotupuPipeRoute_2

The route of the pipe from the Upper Nihotupu dam (shown as the thin yellow line to the south of Scenic Drive). Some of the last section along Exhibition Drive has now been bypassed by feeding into the Huia Aqueduct.

There were already plans to build dams in the Waitakere and Nihotupu valleys, but it was decided that urgent action was required. A simple solution took water from wooden dams in Nihotupu Stream and Quinn’s Creek down a thin wrought-iron pipe into the city via Smyth’s saddle. The failed Titirangi Reservoir was part of this project. The track quickly cut to run the pipe was ‘tortuous’ and subject to continued damage due to slips.  Incredibly part of this original pipe is still in use, now as a local supply pipe along Scenic Drive, supplying water to Titirangi Village.

Emergency Pipe
The portion of the 1901 ‘Emergency’ pipe still in use, from Smyth’s saddle to Titirangi Village

The original pipe was too unreliable and was also too small for the planned Nihotupu dam so in 1912-13 it was replaced with a much heavier and lager cast iron pipe. They made the route shorter by digging tunnels through the spurs, which also made it more resistant to damage from landslides. As the pipe was so heavy a tramway was built to make construction simpler. Part of this was later used in the construction of the Nihotupu Dam and for maintenance of the pipe. The rainforest express tourist train ran along the tracks until the risk of landslides became too big.

NZH19130205.2.117.1-a1-700w-c32_exhibitiondrivepipes
Pipes ready for laying, next to the break-pressure tanks at Smyths Saddle. NZ Herald 5th February 1913
NZH19130205.2.117.2-a1-700w-c32
Official visit to the site of pipe construction. NZ Herald 5th February 1913

The tracks originally went from Titirangi Village all the way up to the dam. Along the first section, the tracks were removed and the road widened to become the very popular tourist drive, Exhibition Drive. When the Nihotupu Water Treatment Plant was decommissioned, the last section of pipe was bypassed by a short pipe to feed into the Huia Aqueduct. This can be seen partly along the Exhibition Drive walk.

Along with most other pipes that form part of the Waitakere Scheme, the Nihotupu pipeline is due for replacement. Luckily tunneling technology has come along way since 1900 – even in 1946 when the Hunua scheme was started, a 5.6km tunnel was dug. Hopefully not too much of the forest of Waitakere Ranges Regional Park will need to be removed.

Titirangi Reservoir

In 1901 it was decided to build a reservoir at Titirangi as part of the Auxillary Supply – an emergency pipe into the city from Nihotupu to fix the city’s desperate water shortage. The site selected was a flat piece of ground just west of Smyth’s saddle. Unfortunately during construction it was found the site had insufficient soil strength and had to be abandoned. A new site was selected and a the plans changed from a reservoir to a much smaller ‘Break Pressure’ tank. This was built right at Smyth’s saddle and later incorporated into the Nihotupu Filter Station.

The emergency supply was an idea created by Henry Atkinson adapted from previous ideas that had been around for at least 40 years. The exact location the reservoir was built is not known, but looks to have been just west of Smyths saddle so would be in the vicinity of the present day Huia Water Treatment Plant.

AS19000615WestPNG
Auckland Star 15th June 1900

A tender for construction was let in December.

AS19001206.2.70.7-a1-426w-c32_tender
Auckland Star 6th December 1900

Construction began almost immediately and the Mayor visited later in December to check on progress.

AS19001224.2.2-a2-405w-c32_visit
Auckland Star 24th December 1900

But suddenly in February things weren’t looking so good. The ground was found to be soft and the reservoir had to be abandoned.

AS19010222_
Auckland Star 22nd February 1901

An engineering review was carried out and it was decided to move the site up the road to directly at Smyth’s saddle and build a much smaller ‘Break Pressure’ tank instead. This was later incorporated into the Nihotupu Filter Station.

Later, ground instability was the cause of more bad luck for the waterworks when the pond at the Huia Water Treatment Plant collapsed.

AS19310907.2.90-a3-435w-c32DamBurst
Auckland Star 9th September 1931
AS19310907.2.78-a1-700w-c32
Auckland Star 7th September 1931

HuiaWTPDam

In 2017 Watercare are proposing to build two 60m diameter high above-ground reservoirs on a site that appears to be in a very similar location to that selected in 1901. Let’s hope they they’ve investigated more thoroughly this time.