What steps can we take in case of silting of borewell?

It is clear that well development and construction was not done properly. A professional driller prepares litholog,time log and variation in the hammer sound and decides about insertion of blank and slotted casing pipe. This practice was in vogue, even when drilling has been carried out in hard rock terrain.

  1. Find out from the driller whether any collapsable zone was encountered at deeper depths where fractured rocks or small boulders intermixed with wet sandy zone was encountered while drilling.This is essential to avoid repetition of the problem even after compressor development of the well. If such zones are present one needs to introduce slotted casing pipes in those zones, using delicate construction procedures. If reasonably potential columns are present at shallower depths one can either seal such deeper zones or ignore such zones by placing the submersible pump at a shallower depth. This operation needs to be done after developing the well using compressor development technique.
  2. Since considerable length of casing pipe has been introduced from the surface any improper anchoring of the casing pipe might also lead to such a problem.

One needs to ensure that both the above operations are done to ensure success. In these operations first check whether the casing pipe has been anchored properly or not.

Contributor: Dr. P Ramachandra Reddy (https://www.indiawaterportal.org/users/paravata)

Reasons and remedies for the silt accumulation in the bore well are,

1. Shallow water carrying silt moves vertically downwards into the bore well along the annular space between the casing pipe and the surrounding geological formation. Construct a trench around the bore well till hard rock is reached and fill it with concrete.

2. Loose formation occurring in between the end of the casing pipe installed and hard rock at depth contributes the silt. You have to install a 5"-diameter blank casing pipe from surface till hard rock is met at depth. You have to then flush the bore well to remove the silt accumulated and install the submersible pump.

Contributor: R Jagadiswara Rao (https://www.indiawaterportal.org/users/rjagadiswara)

Source: https://www.indiawaterportal.org/ask/5591