THE OAMARU TOWN WATER SUPPLY OF 1880
Oamaru is a small town on the east coast of New Zealand (South Island) It was established to service the goldfields of Central Otago and as the port from which North Otago's wool and grain harvests could be shipped to markets around the world.
THE NEED FOR A WATER SUPPLY
In 1870, Oamaru was a pioneer town of just 3,000 people, with its main revenues coming from the woolgrowing industry. Wool was a much sought after commodity, particularly for military uniforms, and wealthy [British and Scotish] immigrant families established very big pastoral holdings in North Otago.
Oamaru is in a dry coastal area with few streams and only two nearby rivers. Both these rivers (Kakanui and Waianakarua) arise in hills which only really receive reliable precipitation as snow in winter. At other times, variable weather and out-of-season deluges, subject both catchments to flash floods or very low and very variable seasonal flows. Neither river has ever been seriously considered for town water supplies.
By 1874, the town had exhausted all the immediately local sources of clean fresh water and the remainder were polluted or ephemeral. Most households collected rainwater off their roofs. The Town Council was forced to debate the options for a public water supply. Both the need, which included the need for a reticulated supply so that a fire service could be established to stabilise insurance costs which were rising and depressing the growth potential of the town, and the options, were vigorously debated and often opposed. Once some sort of concensus had been reached, the Council engaged a civil engineer at a very good salary of £1000 to oversee what was, in effect, a contest for the best design.
The advertisements for submissions went out twenty times in The North Otago Times dated 9th March to 16th April 1875, and on 16,19,22 and 24 March in the Otago Daily Times. No evidence can be found [Papers Past] that the advertisement was placed outside Otago geographic area - which is difficult to reconcile with the scale of the intended works. The prize was £150, which was a substantial sum.
In the opinion of Donald McLeod, the engineer appointed, the schemes that were submitted were all deficient or poorly costed or both and he petitioned the council to be given the task himself. He forwent the prize and designed the scheme, producing about 60 A1 sized sheets of detailed drawings on linen generating two sets [copies], which the North Otago Museum http://www.northotagomuseum.co.nz/ holds in its collection. The scheme was presented to the council on 23 August 1876 and the council voted in favour of commencing the work, which was completed and delivering quite good water to many parts of Oamaru township by 1880.
The water supply was created by digging a gravity driven water race over a distance of 49km from a distant, but big, unpolluted and consistently flowing river (Waitaki) It included 19 aqueducts, 6 tunnels and a reservoir plus reticulation pipes to service the township - these ran 4 km from the reservoir, descending 100 metres into the main street.
The Lord Armstrong | |
|---|---|
 | |
| Occupation | Engineer |
| Engineering career | |
| Discipline | Civil, Mechanical |
| Institutions | Institution of Civil Engineers (President), Institution of Mechanical Engineers (President) |
| Significant design | hydraulic crane, accumulator, Armstrong Gun |
A WATER RACE
Water race appears to be an exclusively New Zealand expression which is approximately equivalent in meaning to aqueduct, channel, flume and watercourse. The Portugese "Lavada" http://en.wikipedia.org/wiki/Levada is probably the nearest physical equivalent of a water race.
Water race describes a man-made open channel for conveying water from one place to another by gravitational flow. Where such a "race" is made from timber or other constructed materials it will be referred to in New Zealand as a flume and where such a flume is supported over space on some sort of bridge structure it will be called an aqueduct. http://www.teara.govt.nz/en/photograph/8621/water-race
The historic uses of water races in New Zealand were for delivering water to alluvial [placer] gold mining sites and for irrigation of pastoral and cropping lands.
Traces of gold mining water races are visible winding horizontally around the hillsides in many of the historic gold mining locations in the South Island and water races, both large and small still dominate the delivery of irrigation water to the plains of Canterbury - a premium dairy farming stock raising and cropping area of New Zealand.
THE DECISION MAKING
The town water supply system, however the water was sourced, was acknowledged as being dependent on a reservoir. The hills close to and right above Oamaru had some small valleys which were suitable as reservoir sites. It was pretty obvious that any of these could, with just an earth dam, provide good water storage at a height above the town which would create a supply delivering water at good pressure. How to get water there, however, and where from, soon became one of the defining questions for Victorian Oamaru.
A few options were obvious, and some less obvious. A few ridiculous ones too, were put forward during the public debate which mainly took place through letters to the editor on The North Otago Times. Local wells were proposed as was utilisation of the few small streams not already in use - where proposers seemed blissfully unaware of their ephemeral nature. Pumping from the Waitaki River with steam driven pumps was possible as there was coal nearby, but the cost and maintenance of this technology was daunting for the council. In the end, a gravity driven water race was decided as the best option. This decision started a complex process of design and construction by McLeod.
The Council needed to be authorised by Parliament to raise the capital funds, and following the passing of the Oamaru Water Supply Act of 18755543, the publication of statutory notices and tendering commenced.
By 1876 the supply and distribution scheme had been designed and land was being acquired. The necessary finance was raised on international financial markets in London and Scotland. Over the construction period, funding had to be increased twice and the empowering legislation ammended twice to cover the final costs. By 1881 when it was finished, the race had cost £136,000 and servicing the loans bankrupted Oamaru for two decades.
DESIGN
Despite the fact that many of the town's citizens were unconvinced that it would work or was even necessary, this major public work needed careful and competent design.
As well as the physical remnants of the Borough Race which are distributed over the route it took, Oamaru still has the 60 sheets of original drawings created by the design engineer, Donald McLeod. Duplicate copies (one reference set for the council and one for the contractor) are drawn on transparent linen in red and black Indian Ink and washed with water colours. The survey sheets are seminal to the project, and are remarkable. They are beautiful artefacts in their own right.
In addition the North Otago Museum holds some 300 additional detail drawings - created over the life of the Borough Race for smaller structures, additions and changes that were deemed necessary and incorporated in the scheme.
McLeod's drawings define and specify construction parameters for just seven (7) major aqueducts, however by 1975 when the scheme was totally mature and actually nearing the end of its working life there were 12 more aqueduct structures of one sort or another, some small and some very large, that were not envisaged nor specified by McLeod. Many of these were for crossing unstable ground where the instability had only become apparent as the race was pressed into service and at higher flow rates than at commissioning.
A UNIQUE ATTRIBUTE OF THE BOROUGH RACE
The Borough Race, as it became called, is a fascinating item of New Zealand's industrial heritage. Not only because was it well made and very functional as a town water supply, but also because the design, from the beginning, included 300HP of "spare capacity" to be available for motive power. This provision, required by the council, makes the race unique in New Zealand, and probably rare anywhere in the world.
Many other urban water supplies in New Zealand provided motive power for a range of users during the last decades of the 19th Century. Water power technology was mature by 1880 and the apparatus and applications were mainly the result of pioneer work undertaken by William Armstrong in Newcastle-on-Tyne in 1846. http://en.wikipedia.org/wiki/William_Armstrong,_1st_Baron_Armstrong.
Armstrong was a lawyer with a deep interest in mechanical engineering. Once in an epiphany whilst trout fishing in a wter mill pond, he had recognised that water wheels did not extract all the energy of water passing through or over them and that in addition, they were only able to extract energy from a water supply delivered no higher than the top of the wheel. The obvious energy in higher waterfalls and steeper longer water courses could not be tapped by any machinery then known. Water wheels operate with unconstrained water falling onto them or passing under them and although undershot wheels could be made to operate in a restriced flume, the management of rotational speed and power was difficult if the water level dropped or was too high as during flooding conditions. Armstrong set about designing a machine that extracted energy from flowing water, at pressure, in a confined pipe.
His water engine is in the Science Museum in London - but as a device for broad utilisation in industry it was passed over.
KEY FACTS
The Borough Race is a long hand-dug channel with a very low gradient and its intake was a long way inland and at elevation. It terminated at a generous reservoir relatively high above town.
The race traverses nearly 49 kilometres from its intake on the Waitaki River. It was carried over 19 streams or across substantial gullies encompassing small streams. This was done by constructing wooden trestle box aqueducts.
Six tunnels were driven to penetrate a number of rocky ridges.
To protect supply quality, all along its route, there were comprehensive provisions to divert any small streams, watercourses and natural run-off generally over the race. This was achieved with wooden troughs called overbyes which were small aqueducts in their own right. They carried contaminated water away from the race. These structures also protected the race from over-filling 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. This happened a number of times in the history of the race.
The water in the balance of the race flowed at just walking pace.
The five tunnels have a combined length of 2.7 km and the 19 timber aqueducts have a combined length of 1.4 kilometres. The tunnels are all still clear and they have a flat floor. Being over two metres high, they could be comfortably walked through to maintain them. They are partly lined with cut limestone and the arched portals are built from bolstered blocks.
The aqueducts are on mixed wooden and limestone (block) piers and they have substantial timbers in their structure. For a water supply, some are quite big. One was very big.
A few were rebuilt in the 1940s with concrete piers. The timber had to be sourced from outside North Otago and was tarred to make it durable. It was mainly kauri totara and Australian Ironbark. All the steelwork was made locally. The aqueducts were originally of rectangular box section roughly two metres by one metre, but all these flumes have been replaced over the years with half round steel.
The fall was calculated to be 1:3964 (although the first four kilometres are steeper and three concrete stepped cascade structures were built to slow the water and break its force in that first section).
CONSTRUCTION
Construction work began in 1877. The race design comprises an open channel about two metres wide and one metre deep, pretty much following the hundred metre contour from the intake on the Waitaki River at about 126 metres above sea level to the reservoir at Ardgowan [above the town] where the water level is 97 metres above sea level. the initial contract was let to a man called henderson but he did not complete the work and was declared bankrupt in^^^&&&***
MAINTAINING THE RACE
The race was maintained along its whole length by a team of about seven racemen, council employees who lived with their families in small council owned and built houses along it. Their job was to clean and maintain the waterway and the land beside it. Each had a specific ‘beat’ to look after.
Because the race flowed slowly, it didn't naturally flush material down its length. While this was a boon for water quality, it required some dedication to keep it flowing and the banks free of build-up and growth.
It was de-watered every Wednesday and the racemen would go into the watercourse to remove plants and contaminants like mussels and waste matter.
Horses and drays were kept at two locations and a centrally located engineering shop and forge was used for maintenance and to create the required hardware. In later years, when the hillsides were more heavily stocked with cattle, the race needed full fencing on both sides for its whole length. This required around 150 kilometres of fencing.
USING THE RACE TO GENERATE MECHANICAL ENERGY
As soon as it was built, and the very large cast iron mains laid throughout the town, the spare 300HP designed into the race was put to work through water engines, turbines, Pelton wheels and other water motors. One water engine rated at 135HP ran a large Haslam refrigeration compressor for the local freezing works. The New Zealand Refrigerating Company had an built an abattoir at Eveline (near the outfall of Boundary Creek) in the late 1870s. Carcasses were taken into Oamaru for freezing on board specially provisioned refrigerated sailing ships and then shipped overseas. The ‘frozen meat business’ was seminal to Oamaru's later growth and wealth and is a whole story in itself.
The NZ Refrigerating Company, realising that ships could turn around more frequently (and profitably) if the carcasses could be frozen on land while incoming vessels were in transit, built a freezing chamber and store in Oamaru. The company was however, continually at odds with the council over its massive consumption of water and the rate it paid for it, and eventually its compressors were run on steam.
By about 1895, grain growing had overtaken sheep farming in North Otago, and large flour mills and grain stores on the waterfront dominated business. These too used the mains water supply to run water engines and turbines for motive power.
Apart from small take-offs permitted for domestic drinking 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 the water was reticulated right around the business area of the town and because it was over 100psi, it was quickly recognised as being ideal for running electricity generating turbines. The first electricity was generated from the town supply in 1887. It is thought that there might have been up to 100 independent DC generating plants in Oamaru at the peak of the technology.
The first DC power was created using a Whitlaws (Scotch) turbine previously installed to grind wheat flour in a flour mill near the harbour. It was connected to a Compton Bipolar generator.
When it was switched on, the Red Lion Flour Mill was lit by 23 electric light globes. Urban myth has it that on that evening Oamaru had more electric lights than London. The generator has been preserved and is in a private electricity museum in Oamaru.
USING THE RACE TO GENERATE ELECTRICAL ENERGY
By 1915 the borough council recognised the potential for reticulated AC electricity to be generated from the water in its supply pipes. It decided to build its own Pelton wheel powered plant running off the water delivered to the reservoir by the Borough Race. Although it took until the middle of WWI in 1917 to see the fruition of this vision, Oamaru became the fourth town in New Zealand to have council-supplied, fully reticulated AC power.
What remains of the Borough Race? The race was in use for 103 years and was de-commissioned in 1983. Some of the remains of the race are still here and the tunnels and a number of the aqueducts survive. The bywash sluice gates and the fence that kept the stock out over the whole 50km (on both sides) can still be traced. Four of the racemans’ cottages are still lived in today.
Sadly all the easement land is now back in private ownership and the artefacts are slowly slipping into the past.
The artefacts comprising the race are not protected by the Historic Places Act which makes it an offence to modify an archaeological site created before 1900, and associated with our heritage. Many of the aqueducts have been demolished. Most of these demolitions can very easily be defended on the grounds of safety. Luckily some of the more remote aqueducts still survive in excellent condition for their age.
The Borough Race is not a listed (historic) item or place and is under-appreciated by the community. Many Oamaru people do not know anything about it and certainly not that it was used to generate electricity so early in New Zealand's electrification history.
However, many of the landowners with 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.
These main cast iron pipes are still in service and have just been exposed for the first time in 133 years.
