Replacing the TBM tunnel with a dual purpose inclined drift tunnel, to facilitate an (underground?) Mine head would require a substantial engineering redesign and put the construction back by likely more than a year. It would also render useless all the bid proposals submitted to date. Not to mention the extra uncertainty of taking a TBM through multiple geologies and the huge amount of extra time built into the model by only operating a single TBM. Bear in mind that the cost of a TBM is almost insignificant on a whole of project basis. As I'm sure everyone knows, in heavy civil engineering time = money. As a rough guide you can bank on at least 5% extra construction cost per year of delay, and possibly as much as 10%. I think SXX is now committed to its current design, albeit likely with fairly minor modifications to the concept provided by its designer, Arup. Undoubtedly the 2 bidders we are told made it to the final bid stage will have value added engineering proposals, but I wouldn't expect these to deviate markedly from the design brief. Remember also that ventilation and emergency egress points are a critical part of tunnel design.
My line of thinking wasn't with regard to a 37km drift to shaft bottom, more along the lines of what's the steepest pitch that the conveyor can safely and reliably operate at? then take the MTS from that point to the shaft bottom, remember no need for two shafts if a conveyer from the pit bottom can take the mined material to Teeside so the amount of spoil would be much reduced anyway to offset the steeper drift of the MTS to shaft bottom, the tunnel would then be at a steeper angle cutting through different layers from the Redcar Mudstone down so would be shorter lengths of tunnel through sensitive geology like the Sanstone Aqufier, I'm only reinventing the wheel here by the way as I know nothing about these matters but it makes for more interesting discussion that what the SP will be in an hour, day, month.
AISI pps 26 - 29 rather than being an expression of intention that YP plan future blending but instead are all about marketing Poly4 as a cost saver/yield enhancer within blends to the growers who are looking for better value nutrition and also only secondarily to potential extra other blender customers. Those pages tell me the deals are all but signed off with the blenders they are in discussion with. Who are then logically going to also start putting feelers out them selves to their grower customer base about the merits of the new 'wonder fert'.
just regarding the inclined tunnel idea: a tunnel of this length requires multiple tbm drives for a quick construction. the current design is for 5tbm drives. also the logistics of building a tbm 1000m underground are too complex. tunnelling and construction companies are currently champing at the bit to get this one started, detail design is currently ongoing and i'd expect sirius to be announcing how they intend to pay for this within the next 12 weeks. then it's chocks away.
Would a 36km drift be cheaper/more feasible than a shaft (actually 1x 1500m: production + 1x 350m: build MTS) plus 36km horizontal tunnel through 1 geo type?
Also bare in mind that operative plus air shafts have to be sunk at DN whatever. The drift would have to have a similar spec to the present MTS - ~ 3 intermediate access shafts (construction likely, safety certainly), they would be ~ 1200, 800, 400m deep. Total power to operate would be around the same. Kit needed would be less.
I suspect the real killer of this 'drift' idea is that you have to go through all that sylvinite, salt, rotten marl and high pressure aquifer Sherwood.. Hard enough getting shafts through that lot.
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