12 November, 2014

Branching out - a drain on resources

Whilst researching my previous posts on the Leigh Grand Junction Bridge, I came across an interesting plan, dating back almost to the Gold Rush, to drain unwanted water from the gold mining operations which had spread from Ballarat all the way down to Mount Mercer and beyond. This rather long post looks at those plans.
By the 1850s, gold was all the rage across the newly-declared colony of Victoria and nowhere more so than in Ballarat and surrounds. Prospectors flocked to the goldfields, hopeful of making their fortune working the shallow deposits of alluvial gold which seemed to exist in such abundance.
By the 1870s however, most of the shallow leads had been worked out and gold was becoming harder to find and more expensive to mine. As a result, this decade saw the arrival of the big mining companies chasing deep leads and quartz reefs. On the low lands to the south of Ballarat, this was especially true. Alluvial gold was there to be found, but much of it lay deep in the ground under a layer of hard basalt, which had flowed from surrounding volcanoes, filling ancient creeks and riverbeds where equally ancient alluvial deposits had formed millions of years earlier. Also beneath the basalt lay the quartz reefs, the products of even earlier volcanic events.
 As the mining companies moved in, they brought with them their blasting equipment, crushing batteries, water pumps and the steam engines required to power them all.
Looking across the Sebastopol workings
The pumps, whilst expensive to run, were vital to the safe operation of the mines and the deeper the mine, the more of a problem water became. Not only did it make removal of auriferous material difficult, if a shaft became suddenly inundated, it could be fatal for the miners below the surface. Whilst buckets could be used to manually remove water from shallower mineshafts with minimal seepage, deeper shafts - often with lateral tunnels known as drives extending at an angle from the main shaft - also suffered seepage and were prone to catastrophic flooding if water were to break through from the more porous layers above the bedrock and enter the mine.
Steam-driven pumps were often used to drain shafts however they were expensive to operate, requiring a constant supply of fuel to keep the engines running. As a general rule, it was only the big mining companies which could afford such equipment and this was true of the area to the south of Ballarat where even today, the names of the towns reflect those of the mines which operated in the area - names such as Napoleons, Durham Lead, Enfield, Grenville and Scotchman's Lead.

Illustration and cross-section view of the Pioneer Gold Mining Company's
mine a little to the south of today's Durham Lead township and the same
distance east of the Leigh. Image held by the State Library of Victoria.
Click to enlarge
So much of an issue was drainage, that in 1877 the Department of Mines requested a report into the feasibility of draining not just a single mine, but the entire Sebastopol Plateau and the area below that known as the Durham Lead - an area extending south from Ballarat towards Mount Mercer and covering an area of around 120 square miles (311 square kilometres) - of which at least 40 square miles (104 square kilometres) was thought to be auriferous. It was felt that draining the plateau would not only open up access to new leads, but also allow for the cheap reworking of earlier claims which either had not been efficiently mined or which had been abandoned due to flooding.
The report was produced by the geological surveyor Reginald A. F. Murray who noted that the watershed of the Leigh River above the Perseverance Mine (previously the Chryseis mine situated near the Leigh about 2km north east of the modern township of Grenville) covered an area of around 200 square miles (518 square kilometres) which he claimed equated to a daily subterranean "percolation" of around 95 million gallons (approximately 360 megalitres) of water through the plateau. But how to drain it?
Map showing Ballarat and Sebastopol mining claims on the upper
section of the plateau. Image held by the State Library of Victoria.
Click to enlarge
Murray proposed a two-part process to effect the required drainage. The first and most detailed stage involved the construction of an adit: a horizontal (or almost horizontal) tunnel providing access to a mine, which could be used for ventilation, removal of minerals or drainage. He stated that the adit should run from the Perseverance Mine on the Leigh, more than 6 miles to one of two feasible points about a mile and a half below the Leigh Grand Junction Bridge and should be funded by the government at a cost of £38,000. It could be constructed in two and a half years by tunnelling from both ends and from eight shafts sunk at intervals in between. Costs would be kept low as the tunnel would not require drilling through basalt, only "Silurian rocks of the ordinary character" and where this was the case, timbering or brick lining to support the tunnel would not be required, offsetting the extra cost of blasting through the stone.

Map which accompanied Murray's report, showing the proposed line of the first section of the adit.
Image held by the State Library of Victoria. Click to enlarge.
The second stage involved extending the adit - using private finance - further north "through or along the old workings of the Durham Lead as far as may be requisite". The report seems a little vague as to exactly how much of the Plateau and Durham Lead would be effectively drained, but an article in the Bendigo Advertiser of 17th December, 1877 suggests that it would drain mining claims from the Durham Company's mine up to Ballarat. In the event, a drainage bill was introduced to parliament in October, 1878. It was withdrawn a month or so later, only to be reintroduced the following year, this time with two suggested alternatives: Murray's plan, or a scheme which involved the use of steam pumps to do the work of the adit. It would seem that nothing was resolved as the issue of draining the plateau was also in the newspapers in 1881, 1882 and again in 1886 when the Mines Department called for expressions of opinions as to how best to drain the plateau. The following year, the issue was put before a Parliamentary select committee where three proposals were tabled: 1) to drain the plateau entirely by pump 2) to extend the adit all the way up to Sebastopol or 3) to drain the lower Durham Lead area using the initial adit suggested by Murray, with pumps then being used to drain the upper section.
Many opinions were put forward for and against each option. There were those who felt that whilst cheaper, the pumps would not provide adequate drainage, whilst others suggested that Murray's estimates fell far short of what would be the true cost of constructing the adit. It was also suggested that to use only a system of adits would require around 19 miles, 10 chains of tunnel with a further 15 miles of tributary adits requiring the sinking of 38 shafts - quite a different story to Murray's proposal and significantly more expensive! Even then, the financial returns suggested by Murray were by no means guaranteed and nor was the drainage itself, it was claimed.
By November, 1889, the issue formed part of a broader royal commission into gold mining in Victoria with the same claims and counter claims about the efficacy of the suggested processes being put forward and some witnesses even claiming that there was little gold left in the area anyway.
Once again it seems no decision was reached and in 1901, 1902, 1903 and in 1905 attempts were still being made to secure government funding for some form of drainage, this time however with the added twist that "by his [the mining engineer's] scheme the adit would serve as a main sewer for the deep drainage of Ballarat and also allow for increasing the water supply."
Again, no definite action was taken although government grants were provided in some cases for private companies.
Then, finally in 1935, the media was abuzz with the news that the plan to construct a "20 mile" adit to drain the plateau had once again been proposed. This time a London company was prepared to spend what was now estimated as being the £1,000,000 required to complete the work which, the papers noted, had lapsed for the last 70 years owing to the expense. However, despite media declarations that drainage was imminent, there is no further mention of such a scheme past this time.
The plateau, it seems, was not drained, the adit was not constructed and the flow of water into the Leigh River was not changed as a consequence of such action, although it is interesting to speculate what the environmental effect of such a plan might have been.

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