Running discussion on SP, page-21037

Thanks for the reply. I see there has been a bit of discussion on the dewatering which I haven't fully read yet. I had a bit of a look at it.

To work out a minimum rate required I made a few assumptions:

1) To complete dewatering of both pits by the beginning of December and assuming pumping started 1 July gives 150 days

2) Assumed both pits are 20m deep average

Using Google Earth

The M’Pete pit is approximately 36,000 m2

The Roche Dure pit is approximately: 250,000 m2 minus Roche Dure Island 18,000 m2 = 232,000 m2.

Total area of the two pits = 268,000 m2.

If the average pit depth is 20 m then the volume= 5,360,000 m3
or separately
Roche Dure pit volume is 4,640,000 m3
M’Pete pit volume is 720,000 m3

So to just dewater Roche Dure pit before the start of December the minimum rate of dewatering needed is 4,640,000 / 150 = 30,933 m3/d = 1,289 m3/hr = 1,289,000 l/hr.

Now apparently the large unit shipped in will do around 350 l/s = 1,260,000 l/hr which would be just enough to dewater the Roche Dure pit by December assuming no break downs. Using additional local pumps and gravity feed will increase the probability that the dewatering will be a success within this time frame.