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Post by RKC on Dec 15, 2011 9:47:27 GMT 12
G'day, River dredging banks on elusive gold "A new gold dredge made an impressive sight as it travelled through Roxburgh yesterday on its way to its temporary base at Commissioners Flat, south of the Roxburgh Dam.
Built in Nelson for the Cold Gold Clutha company, the suction dredge will attempt to gather the gold left behind in the rush days between 1860 and 1920". www.stuff.co.nz/southland-times/news/6141636/River-dredging-banks-on-elusive-goldRegards, Rob (RKC) |
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Post by RKC on Dec 15, 2011 20:43:19 GMT 12
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Post by billincostarica on Dec 17, 2011 12:24:06 GMT 12
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Post by RKC on Dec 18, 2011 18:27:47 GMT 12
G'day,
The following description of the dredge is from the ORC Resource Consent Application (description of the proposed dredge at that time, dated 31 Jan 2008).
"The dredge comprises a "venturie" type system fitted to a 15 metre (m) by 6 m floating pontoon, fitted with a Southern Cross 100 kilowatt motor which draws material via a 35 centimeter (cm) inductor nozzle. Although yet to be constructed, the plans of the dredge include a central operators room, where the "operator" will be able to monitor and direct the nozzle in the gravels via a hydraulic arm fitted with a camera. Meterial will be drawn up via the nozzle and passed over the riffle-box, where the gravels and silts are then returned to the watercourse. Gold and other heavy minerals are caught behind the riffles, perpendicular to the laminar flow, where they are concentrated using twin jigs and Knudson concentrators and then collected at the end of each session.
Surface water will be taken at a maximum rate of 50 litres per second (l/s), with a daily maximum take of 3,600 cubic metres (m3). All water will be returned directly to the watercourse at the point of take and as such, it will be considered non-consumptive and threrefore not subject to an allocation or efficiency assessment."
Regards,
Rob (RKC)
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Post by RKC on Feb 10, 2012 15:45:33 GMT 12
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Post by RKC on Feb 13, 2012 8:10:32 GMT 12
G'day, Dredge in water ready for testing"Cold Gold Clutha Ltd's dredge is finally on the Clutha River and ready to begin work.
The 24m suction dredge was taken to the banks of the Clutha, near Coal Creek, on Thursday but the truck it was on became bogged in the soft riverside gravel and workers spent two days digging it out and clearing a path for it to the river."www.odt.co.nz/regions/central-otago/197520/dredge-water-ready-testingRegards, Rob (RKC) |
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Post by powderburns on Feb 13, 2012 20:14:46 GMT 12
They had to call contact to open the sluice gates at the dam to float her. Tee hee.
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Post by RKC on Feb 13, 2012 20:49:48 GMT 12
G'day powderburns, The Clutha is probably running very low at present ... but once they start they will probably have no problems floating the beast. It will be interesting to see how they cope with the sudden rises in water level that regularly occur in the lower Clutha when Contact Energy lets water go. I was told by profession dredgers who worked the lower Clutha in the 80s and 90s that the sudden rises in water levels made it very difficult to dredge there with diver-controlled suction/eductor dredges. At least with this dredge all the crew will be out of the water, and because of its size any sudden rise in the water level of the river might not effect them negatively. Also they should be able to easily run the dredge right through winter because they don't have any divers down underwater. If the use of a suction hose to lift the auriferous river wash does not work out maybe they could try a clamshell dredge www.youtube.com/watch?v=efUWMBua58oRegards, Rob (RKC) |
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Post by Deleted on Feb 13, 2012 22:19:04 GMT 12
Hi Rob,
Diving in the winter didnt stop us. Probably warmer in the water with a heater than out in the frost and snow. Only bad bit was climbing into a frozen wetsuit.
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Post by RKC on Feb 14, 2012 9:11:57 GMT 12
G'day homesouth,
These days it would be unlikely to be able to find even one fit young person who would be tough enough to dredge during an Otago winter on a production dredging project. And nearly as unlikely to find someone who could work for at least 6 hours underwater, even during summer. And it would be practically impossible to find someone who has the fitness to work underwater on a production dredge at any time of year who also has the intelligence and skills to work a nozzle efficiently.
I had a good laugh to see the divers on the Bering Sea Gold TV show come to the surface after less than 2 hours on the nozzle, and collapse with exhaustion. And dredging in a fast flowing river, like the Clutha would be much more physically taxing than diving in the relatively still water off Nome on a calm day.
Regards,
Rob (RKC)
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Post by powderburns on Feb 15, 2012 4:25:00 GMT 12
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Post by RKC on Feb 15, 2012 20:16:57 GMT 12
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Post by RKC on May 15, 2012 22:12:41 GMT 12
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Post by RKC on Sept 12, 2012 9:53:44 GMT 12
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Post by RKC on Oct 20, 2012 11:13:52 GMT 12
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