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Friday
Apr272012

There's a hole in my bucket dear Lisa, a hole......

This is the PR release on The Hole this morning.

They are not exaggerating - it is a large hole indeed, and it will take a great deal of engineering work to restore the road. Just as well that the 'repaired' road surface did not fall in following the January work - someone may have disappeared without trace. A case of under-estimation by the sound of it.

I suspect that the diversion will be in place for some time.  

Update on SH25 mine shaft hole

State Highway 25 at the north end of Thames will remain closed until repairs are completed to cover an old pump shaft that was exposed when the road sank last week.

NZ Transport Agency Waikato State Highway Manager Kaye Clark says the shaft is the same location as a smaller hole which appeared in the road in January this year.

"When we excavated the hole in January initial investigations indicated that the shaft had been back filled and it seemed some settlement in the fill was what caused the road to sink. This time we have excavated much further and have now exposed the full extent of an old pump shaft.”

Historic records indicate that this may be the site of the first 'Big Pump’, constructed for the Thames goldfield in 1872 and closed down in the early 1900’s.

The shaft is about 6m by 4m and it is unknown if it had been back filled previously or how it was covered over as there is at least 5 metres of water in the shaft. Local historians have been involved and discussions are also being held with the Historic Places Trust to ensure that the shaft is well documented and recorded.

"The hole will require bridging over to allow the road to be reinstated and design work on this is currently underway. It is essential that we provide a long term solution and having to span such a wide opening so as not to put any loading on the shaft’s walls is providing our engineers with some challenges."

Mrs Clark says until this work is underway it is not possible to say how long the highway will remain closed, however the NZTA will be carrying out the work swiftly as possible to minimise disruption to traffic. A short local detour is in place and is not expected to cause significant delays for motorists.

   

"The hole" - those granite blocks are about 800mm x 400mm X 400mm - they appear hand worked, and  their size gives support to the theory that this is the site of the the legendary 'Great Pump' installed in the late 1800s by Cornish mine pump engineers, but if someone out there has better information please provide same through Comments.  

 

 


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Reader Comments (1)

This shaft was commenced in 1868 by the Imperial Crown company, who also installed a pump. Several years later, the adjoining claims, being, Tookey’s, Caledonian, and Golden Crown formed, with the Imperial Crown company, the United Pumping Association, with the intention of deepening the existing shaft and pumping water from a greater depth so that each of the four subscriber companies could prospect and mine at greater depth.
During the period 1869, 1870, and 1871, each of Tookey’s, Caledonian and Golden Crown were working on very rich stone, and were keen to continue prospecting at greater depth. It became evident that the existing pump would not cope with the volume of water being encountered at the greater depths, and so a new pump was commissioned and installed by Mr Errington, engineer, in 1872. The pump so installed was the largest in the southern hemisphere at the time of installation, being able to pump 1,200 gallons of water a minute. The pump and associated equipment was made in Australia.
For those with a technical interest the pump-lifts were 25 inches in diameter and the engine was an 81-1/2 inch cylinder Bull engine, converted from a high pressure to a condensing engine. There were three Cornish boilers with Galloway tubes and mountings with each boiler measuring 33 feet by 6-1/2 feet. It was stated that 26,000 cubic yards of stone, quarried from the Hape, was necessary for the foundations and to line the collar of the shaft.
The installation of the new pump was made more difficult because the existing pump installed in the shaft had to remain operational so that the four subscribing companies could continue mining and prospecting operations.
In July 1872 the initial trial of the pump was held. It was reported in the Daily Southern Cross on 30 July; “... full steam pressure was for the first time brought to bear upon the ponderous engine by way of a preliminary test. The effect was in every way satisfactory. The engine and pump worked smoothly and without the least vibration or noise. ...” Mr Errington, the engineer, was, understandably, pleased with the installation so far. By 21 August, the pump was in full operation, draining the water by four to six inches per minute. The shaft reached a final depth of 645 feet.
It was still open in 1911, at least to a depth of 444 feet and in use, with seven others I think, by the Drainage Board. The Big Pump appears to have been dismantled in 1919 or thereabouts.
With the collapse of the old Big Pump shaft for a second time comes an excellent opportunity to explore one of the exciting technical developments on the Thames goldfield.
The shaft location, being on the western edge of the state highway, was remediated in January, the time of the first collapse, quickly, with no time allowed for archaeological exploration and site recording.
With an average of around 4,000 vehicle movements a day over the site, there is little to wonder at the need for speed in fixing the problem.
But with the quick fix, an opportunity was lost to capture detail about the shaft and gain an understanding of the place the old Big Pump had in the development of the goldfield.
But the collapse revealed something else. It revealed an attitude; that, perhaps, ‘the authorities’ do not place much value on our history, at least as reflected in archaeological remains, rather such matters as the collapse are viewed from an engineering perspective and the urgent need to maintain significant infrastructure assets in an operational state.
The pumping history of the Thames goldfield is significant. The United Pumping Association shaft, later referred to as the ‘old Big Pump’, was one of the biggest pumps in the country when it was constructed in 1872, on the site of the Imperial Crown shaft and pump. The operation of this pump was intended to allow adjoining companies to continue deep level prospecting and mining; this at a time when the Caledonian, Tookey’s and Golden Crown, three of the most prominent early Thames mines, particularly were facing declining returns. In much the same way, the Thames Hauraki pump (also called the Big Pump) was constructed in 1898 on the site of the Queen of Beauty shaft and pump (now the Bella Street Pumphouse Museum of Industrial Technology) and was instrumental in allowing foreign joint venture capital to explore the goldfield at the 1,000 foot level. The Big Pump was the biggest pump in Australasia and it’s construction was a major technical achievement and assisted in maintaining activity and employment within the industry. It also provided an opportunity for some hope that the industry might once again be a big player in the local economy. A forlorn hope, as it turned out.
It is good that there is an archaeologist involved in the remediation work at the UPA Big Pump collapse site because we can be assured that the site will be properly photographed, measured and recorded as an archaeological site and treated with some dignity. It is to be hoped that the remedial engineering works that allow the road to reopen do not destroy the site and further impoverish Thames in the loss of a chance to reflect on our spectacular engineering and mining history. Maybe now, Thames residents might begin to wonder at the amazing history of our town.

May 2, 2012 | Unregistered CommenterRussell

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