Taking samples from old wells

[MirJev]

Hi everybody.
Water quality sampling is to be done for 7 wells. The problem is that these wells are currently out of service and they have been out of service for almost a year, but the authorities want to put them back to work and they need to check for the quality of the water.
The question is:
For how long should they "flush" the water out, before taking the samples in order to collect valid samples? Bare in mind that all of the water being pumped out is going to be wasted, and that electricity cost for the pupms is high.

Thank you in advance for your answers.
Mirko

 

[ashtree]

Pick a number of easy field tested parameters eg: conductivity, pH , turbidity.
Sample the well when you start pumping and test for the parameters chosen.
Test every couple of hours for a start and record the results.After a while you will have a good feel for the results and you may be able to test less frequently perhaps once per day.
I can't give any advice on how long it might take but continue to test and pump until all the parameters stabilize and flat line.

It is after the results flat line that you should be able to consider getting proper samples, tested in a lab for all the parameters that you desire.
Some parameters not tested in the field might still require further pumping but it will be likely if you follow the process described that most of the old water will be gone and your samples will represent the actual quality of the well.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[MirJev]

Thank you for a great advice! The only issue is that we have no field engineer on the location and it is very far from our headquarters, but maybe we could hire somebody...