That seems to be the plan - enough capacity to store the whole topside lake, which seems to be planned at 500m x 500m (depth 10m). No idea how feasible or econo

That seems to be the plan - enough capacity to store the whole topside lake, which seems to be planned at 500m x 500m (depth 10m). No idea how feasible or economic it will be compared to caverns from hollowing out a mountainside.