RE: My Calculation of hole If you take 160x325m = 52000 m2 it's square meter and no cubic meter. So you have to take an estimate for the width, let' s say 5m, so it will be : 52000m2 x 5m = 260'000m3 (cubic meter x 3 tons = 780'000 tons x 4%, so it's now 31'200 tonnes @ 7'500 = 234'000'000 $fg