We had recently had three borewells drilled in our rather large apartment situated in the Mahadevapura area of Bangalore (former CMC). Of this one borewell yielded about 1 1/4" of water at 400 feet and we went down to 600 feet. A second borewell yielded again 1 1/4" of water at various levels and we went down to about 800 feet before stopping. A third borewell yielded less than an inch of water which was again terminated at 800 feet as recommended by the geologist report and data from other borewell drilledin our area. We also have an existing borewell with decent yield in use, pump at 350 ft depth. Builder had it drilled and we do not have much info about that borewell.
I wish to ask a question about the third borewell (1 inch yield, 800 foot deep). Hard rock was hit at 26 feet. Driller (supposedly well known in Bangalore) lowered 6.5 inch heavy gauge MS casing to this depth as well as a 10 inch PVC pipe. Water was struck at around 450 feet and 600 feet and then we went down to 807 feet, cleaned and capped the borewell. There was an enormous amount of rain in Bangalore during and after the drilling. Yesterday (April 24), we found that the water level in this borewell was just 10-20 feet below the surface (I could see it from above!). Is this normal? What could be the explanation? Could water be leaking into the borewell from somewhere? Could the casing pipe be cracked - say at weld? I am worried about any surface run off getting injected into the borehole and contaminating the ground water. Open to any suggestions on what to look for and fix.
We did not see this phenomenon in the other two borewell that had been also drilled at around the same time.
Thanks,
-Sanjay
Bangalore
PS1: We have an issue of sub soil saturation in our area. Rock level is shallow. In parts of out apartment, making a hole 20 foot deep will yield water also.
PS2: Until a year back, our apartment was receiving good supply of city (Cauvery water), but has now massively dropped and tanker water quality, upon testing was horrible. Hence the decision to go for these new borewells. Also trying other cobnservation, harvesting and recycle measures.