If you've used cement/bentonite to grout the hole you might want to leave that for a few days to set before you start aggressively pumping and surging water up and down the column but I can't think of any other reason not to do it immediately.
Clive Williams
CGeol SiLC
Mott MacDonald, Cardiff
Principal Contaminated Land Consultant
Prif Ymgynghorydd Tir Llygredig
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