barrelroll replied to flintgreasewood's topic in Larger Scale Placer Mining Operations and EquipmentI'm still a green bean when it comes to mining and have been in a underground hardrock mine a couple months. The other day I was bored mucking and somehow this popped into my mind. I wonder if you could mine it underground cheaper per yard of pay than you could removing 50' of over burden. A lot of our older workings have steel arches every 3-4' and then the voids are filled with concrete to create a solid tunnel. What about doing a hualage ramp/ tunnel with steel arches filled with concrete and then a concrete ramp floor going down? Basically you would be making a big steel and concrete culvert going down and then continue the haulage tunnel down the valley. Possibly timber and use your existing shaft as a secondary escapeway and intake or exhaust vent shaf tied into the main haulage tunnel. Mine pay gravel in the winter when it's frozen either drifting or using room and pillar with temporary ground support if necessary. At the end of the underground season pull the temporary ground support and close off access to the exhausted workings. I'm guessing during the summer you would have to dewater the tunnel but that water could be used for processing. If you have 10-12' of pay you might be able to get away with conventional surface equipment though underground equipment is stupid tough. I run a cat r1600 LHD and there's no way it's surface equivalent would hold up to the abuse of bouncing off the rib and moving around rocks all day. Though you could buy a used loader every year for what a used 1600 costs. Your pay might be easier on equipment than hardrock is on equipment. Would a breaker on a small excavator work on the pay to break it up? I think you could run a pretty efficient operation with an excavator breaking up pay, a loader loading it or possibly even hauling it to the surface, and then if it's worth it a couple rock trucks. So between 2-5 guys a shift and not dealing with much if any overburden. This method could be "modular" and you could have several crews working on several faces at the same time all using the same tunnel with some traffic controls in place. Any idea on how to start crunching the numbers? Your initial startup costs would be high putting in your ramp and haulage tunnel. It would involve pumping in 1000's of yard of concrete and lots of steel. You would also have your power, ventilation, and dewatering to deal with. At the same time buying a couple d9's or 10's, a large excavator, a couple haul trucks and moving 50'+ of overburden isn't cheap either. Once you were on the pay you would have higher wages being an underground operation but lower fuel costs.and equipment maintenance not having to have huge equipment.