hill end history, page-3

Hi Bernard,

The local downamper certainly seems to be kicking along today. The comments about brownfield sites would have applied equally to Cadia, The single largest goldmine in NSW right now and a very profitable operation for Newcrest. Cadia is only about 50km from Hill End as I recall but it would be a couple of hours by road. The reality for brownfield sites is that they are always good places to look for new deposits. The "old timers" worked under very difficult and dangerous conditions but were always limited by available technology. Invariably, they left more hard rock ore than they mined. They even left some colour in the creeks and the "paddocking" technique they used to look for near surface nuggets is no match for the modern metal detector. The famous "Hand of Faith" nugget is marked with the scrape of an old timer's pickaxe.

Underground, and old timers were at even more of a disadvantage compared to modern miners and explorers. The water table problem is well known but mine ventilation was equally problematic. Old timers relied on natural ventilation and 50m from a shaft was about the foetid limit. Nowadays, ducted air effectively air conditions underground mines.

Ground support is another aspect of mining being improved by technology. Timber props were used almost exclusively at Broken Hill when I first ventured underground in the early 1970's. Timber props still have their place and I've seen them in the stopes at Hill End. Most of the ground support though is by split sets with mesh as needed. Fortunately, ground conditions at Hill End tend to be very good. Advantages of split sets are that they use the rock itself to provide strength, they grip more strongly when there is some ground movement and they are inserted using the same air drill that does the blasting holes. The split set was invented in the late 70s as I recall.

I wouldn't ever want to dismiss the old timers as incompetent. They were limited to the technology that was available to them at the time while our technology gives us better access and much more comprehensive data. The craft of mining extends thousands of years into the past and we benefit from past practices as well as modern innovation. I mentioned timber props being used in the stopes. Using some timber underground isn't just a tradition but a useful safety device. Even tiny ground movements will bend a pit prob and make it creak. Miners use the term "talking" to describe noises from the props. If the pit props are talking, it's time to leave.

The downramper quoted from a DPI "Primefact" The references are certainly worth reading and have been discussed in these threads before. They are digitised versions of older publications called "Minfacts". I looked for Minfact publication dates but couldn't find any. I think some of them at least dated from the mid 1970s. To the best of my knowledge, the only changes made to the Hill End Minfact are metric conversions of distances and masses. The downramper neglected to mention the disclaimer at the end of the Primefact on Hill End. Here it is:

"Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (February 2007). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of New South Wales Department of Primary Industries or the user’s independent adviser."