Ann: Hera Project Update , page-13

Arsenic, my thoughts are:
In situ seismicity is unlikely to be a problem at this depth (reasonably shallow). The important thing the engineers will be watching for is mine induced seismicity and how the surrounding rock mass reacts to us humans disturbing it, ie how the stopes are sequenced. At shallow depth, you can (usually) pretty much do what ever sequence you want but at depths below say 500m the sequencing really starts to play a part. Beyond 1000m, you are beholden to the sequence and any sequencing sins from the past. I haven't looked at or read any info on their proposed mining method. They might have some info on this.
By stope sequencing, I mean the order in which the orebody is extracted. This type of ug mine usually has to leave intact pillars due mainly to scheduling. Over time these pillars bear more and more stress until the stress is too much and the stress field redistributes. Redistribution is usually on a localised level and is the mine "talking". Paying attention by measuring and recording this "talking" is the key to a geotechnically safe mine and safe stope sequence ( as opposed to "high grading" or rape and pillaging).
It is unlikely the tunnels will contribute to mine induced seismicity at this stage, but good geotech management and properly laid out levels will ensure that over time the combined tunnels hold up and minimise contribution to mine induced stress.

Wall stability will depend on the jointing and structures in the rock mass. No doubt the engineers would have looked at the trade off between stope dimensions and wall stability and accounted for an appropriate level of stope waste dilution. This all affects operating costs. They won't know for sure until they start mining it.

Each mine is unique and part of the challenge is to mine the orebody in a way that sustainably maximises value for all stakeholders (workers, investors, community, t/o etc). It's why mining shares are quoted on a separate index to industrials!


Glta
Please dyor

Cheers