Saturday, September 4, 2010

Guest Post: The Oamaru Borough Water Race

(Out of the blue, I receive an email this morning from Oamaru historian Bruce Comfort, including two of his articles on the industrial heritage of his area. I like emails like that, and especially when folks like Bruce give me permission to share his work with you here on Timespanner. This is the first article. The second one, on the Oamaru Freezer Building, is here.)

THE BOROUGH RACE

In 1870, Oamaru was a pioneer town of just 2000 souls. It was situated on the east coast by the Southern Pacific Ocean and a small peninsula gave its beach some shelter and thus afforded a rudimentary harbour.

There were no trees, and it was dry and harsh in summer, but because there were no trees when the European settlers arrived, the land was immediately available for grazing sheep on the predominantly palatable native grasses.

In the late 19th century, wool was a much sought-after commodity, particularly for the military uniforms used by armies fighting in the harsh Northern Hemisphere winters. Wealthy families established very big pastoral holdings in North Otago, and huge flocks of sheep were introduced to meet the international demand for wool.

The town's first "indigenous industry" was the wool industry.

It did however do very well out of gold mining, and some of its pre-industrial wealth was derived from it. Prior to 1870, Oamaru served as a service town for those gold miners who worked small claims in the Dunstan mountains and creeks running out of them. The Waitaki is not a gold bearing river and was never dredged, and so the "gold mining industry" of the Clutha and Central Otago never came to Oamaru. It did however thrive on its contribution to servicing the Otago and Central Otago gold rushes and subsequent dredging and quartz mining industries.

Oamaru is over 35km from here in a straight line, or 45km by road. You will be there in about an hour or so.

The town has a number of quite opulent classically designed limestone buildings, which people travel the world to see. It also has a wonderful old harbour and a revolutionary breakwater which was built out of concrete in 1878. It has a well deserved reputation for its nearly intact Victorian harbour-scape.

Oamaru's Victorian elegance was founded on money from the wool trade, and later from wheat growing, but it is its public water supply which I want to celebrate with you this morning, a thing much less attractive than the white stone buildings and so, largely unrecognised for its elegance, which derives from its concept, design, execution and utilisation.

Water supply for the town, in 1870, comprised wells and springs and a small ephemeral stream. Most households collected rainwater off their roofs.

The stream became polluted and muddy and the wells became unreliable. As the town grew, so did fire insurance premiums, and so a fire brigade with access to a reticulated town water supply became urgently needed.

Some hills close to and right above town had deep gullies which were very suitable as reservoir sites. Any of these could, with just an earth dam, provide good water storage at a height above the town which would create a water supply delivering water at about 150psi.

How to get water there, however, and where from, soon became the defining question for Victorian Oamaru.

A few options were obvious, and some less obvious ones were proposed.

Pumping up from the Waitaki River was possible with steam driven pumps and there was coal nearby, but the cost and maintenance of this "new" technology was daunting for the Borough Council and in the end, a gravity race was decided upon. Simply saying "decided upon" obviously minimises the controversy, acrimony and drama behind the decision, but that is another story.

It would be one which many practising engineers would recognise today.

Commencing with public notices and tendering in 1875, a public water supply and distribution scheme was designed over a two year period whilst land was acquired, legislation passed, and the finance raised on international markets in London and Scotland.

The water race was designed, unlike the water races of the gold mining era which were built "on the run" and with water flowing in them to help get the grades right. As well as the physical remnants, some of which we will see on this trip, Oamaru still has the 140 sheets of original drawings, on linen, done in red and black Indian Ink by the design engineer. A folio of these water coloured (washed) drawings will be available to look at when we get to Oamaru. They are beautiful artefacts in their own right. The survey sheets are seminal to the project, and are remarkable.

The Borough Race, as it became called, is a fascinating item of industrial history because, not only was it well made and very functional as a town water supply, delivering very potable water from an unpolluted source, but because the design, from the beginning, included 300HP of "spare capacity" to be available for motive power. This provision is what makes the race unique in New Zealand, and probably rare anywhere in the world.

The Borough Race terminated at a reservoir relatively high above town. This entailed a long channel with a very small gradient and its intake was a long way inland and at elevation. Here at Bortons, we are already nearly 6km downstream from the river intake.

The race then goes 41km from here to town. It was carried over about 20 streams and this was done by constructing wooden trestle box aqueducts. It also had to penetrate a number of rocky ridges and five tunnels were driven to achieve this.

To protect supply quality, all along its route there were comprehensive provisions to divert any small streams and watercourses and natural run-off, generally over the race.

This was achieved with wooden "troughs" (they will have a name - but I don't know it!) which were small aqueducts in their own right, to carry dirty water from the hillsides over the race and not into it.

These structures also protected the race from "overfilling and over topping" during heavy rain. If uncontrolled run-off entered the race in quantity, it would overload and over top the banks, causing catastrophic erosion. In actuality this happened a number of times in the history of the race. North Otago is generally a dry-climate area but it can rain very heavily. Larger streams were all crossed in aqueducts.

Construction work began in 1877.

The race comprises a hand dug open channel about 2 metres wide and one metre deep, pretty much following the 100 metre contour from the intake on the Waitaki River at about 126 MASL, to the reservoir at Ardgowan [above the town] where the water level is 97 MASL. The race was unlined and only puddled in a few places. It leaked but the leaking eventually stopped as silt built up and the banks became colonised by water plants and other organisms.

Its fall was calculated to be 1:3964 and the water flowed at just walking pace. Its total length is about 47km. We will see just 21km of it today. This is not long by comparison with say the Western Union Canal in the UK, but remember this race was just for drinking water for a very small town and not built as a river of commerce between densely populated industrial cities.

The five tunnels have a combined length of 2.7 km and the 19 timber aqueducts have a combined length of 1.4km.

The tunnels are all still clear and they have a flat floor. Being over 2 metres high, they could be comfortably walked through to effect maintenance. They are partly lined with cut limestone and the arched portals are all built from bolstered blocks.

The aqueducts are on mixed wooden and limestone (block) piers and they have quite substantial timbers in their structure.

A few were rebuilt in the 1920s with concrete piers. For a water supply, some are quite big. One was very big.

The timber had to be sourced from outside North Otago (remember NO trees!) and it was tarred and the steelwork made locally. The aqueducts were originally box section roughly 2 metres x 1 metre but all these flumes have been replaced over the years with half round steel channels.

The race was looked after along its whole length by a team of Racemen (about 7) who lived with their families in smallish houses along it and who cleaned and maintained the waterway and the land beside it. It was de-watered every Wednesday and the racemen would go into the watercourse to remove detritus and mussels (bivalves) and grasses and weeds which they cut with sickles and scythes. In addition, horses and drays were kept at two locations and there was a centrally located engineering shop and forge to create the required hardware. It was fully fenced on both sides, for its whole length - representing probably over 150km of fencing.

The race cost £136,000 in 1880 when it was finished and the cost bankrupted Oamaru for two decades. It delivered water to Oamaru for 103 years.

Apart from small take-offs permitted for domestic and stock watering along its length, the intake water was delivered in its entirety to Ardgowan. The race was not used for irrigation of pastoral land, but in the 1960s some irrigation of orchards and berry farms was permitted.

As soon as it was built and the cast iron mains laid throughout the town, the spare 300HP was put to work through water engines, turbines, Pelton wheels and other water motors. There was one water engine rated at 135 HP which ran a very large refrigeration compressor for the local meat works.

By about 1895, as grain growing had supplanted sheep farming in North Otago, large flour mills and grain stores on the waterfront dominated business and these too were able to utilise the mains water supply to run water engines and turbines for motive power. There are water engine remnants in a few of the old grain stores and wool stores in the heritage parts of town.

Because the water was reticulated right around the business area of the town and because it was at about 150 psi, it was also quickly recognised as being ideal for running electricity generating turbines, and the first electricity was generated from the town supply in 1887. DC power was created using a genuine Pelton designed (patented) wheel connected to a bipolar Compton generator. This, just 3 years after the Pelton wheel was patented in America.

When it was switched on, the Red Lion Flour Mill was lit by 23 electric light globes. On that evening, Oamaru had more electric lights than London and we still have the generator here in town!

It is thought that there might have been up to 100 independent DC generating plants in Oamaru at the peak of the technology.

By 1913 the Borough Council, recognising the potential for reticulated AC electricity, decided to build its own Pelton wheel powered plant running off the water delivered to the reservoir by the Borough race, and it although it took until 1917 to see the fruition of the vision, Oamaru became the third town in New Zealand to have Council supplied, fully reticulated AC power.

The race is still there. The tunnels are still there, and a number of the aqueducts survive. The bywash sluice gates are still there and the fence that kept the sheep out over the whole 50km, on both sides, can still be traced.

Four of the racemans cottages are still lived in. I hope you find it as inspirational an example of Victorian engineering, as I do.

The artefacts comprising the race are protected by the Historic Places Act which makes it an offence to modify anything associated with our heritage and which was created before 1900.

The Borough Race is not a listed (historic) item or place and in fact it is under-appreciated by the community.

Many local people do not know anything about it and certainly not that it was used to generate "our own electricity" early in New Zealand's electrification history, however many landowners with family land occupation histories that intersect the place and the period when the race was operational are well aware of it, and its stories, and that it had significant potential right up until the day it was de-commissioned.

Sadly all the easement land is now back in private ownership and the artefacts are slowly slipping into the past.



Bruce Comfort
November 17th 2009

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