Couple of months back I got a Bore well drilled at Koramangala Bangalore on a fairly elevated site compared to the surroundings. Drilling details as given by the driller are as follows.
0-12 ft Reddish Brown clay
12- 44 ft Yellowish Brown Sandy Clay (Damp)
44-64ft Very Soft Rock
64-160 ft weathered/medium hard rock in patches with quartz. Number of dry fractured zones.
160-324 ft light gray/ pink granite in bands.
Fractures with water.
32 ft-Damp (covered by steel casing)
80/120 ft Low yield (Covered by casing)
20-208 ft- Expected yield of about 2700 LPH.
Final depth 324 ft.
First 167 ft was covered by 6 ½” steel casing. A one kw submersible pump was installed at 185 ft to find that it was pumping clear water after some initial murkiness. Next day while trying to measure its yield after overnight’s recuperation about 500 liters of muddy water was pumped out before water stopped completely and suddenly while the pump was still running. Subsequently it was found that the pump was trapped in a pile of mud. It was released by washing the well during which first came lot of silt then fine sand and subsequently course and very course white sand came. About 210 ft of 4 ½” PVC pipe including 60 ft 0.5 mm slotted segment in the beginning could only be lowered that is another 114 ft in the bottom of the well continued to remain blocked. The pump was then installed inside the PVC casing at about 198 ft including the pump. Subsequent results are very disappointing as the yield is only about 240 liters per hour of mildly stinking water and after pumping this meager amount for 10 days the pump again stopped functioning and on inspection there was no electrical continuity to the motor and when we tried to pull it out for reconnection, the pump is stuck in a pile of silt and soft mud. It has not been retrieved so far.
Do I have a hope for this well and if there is, can some body tell me what I should do.
The site is now dug up with lot of foundation pits and there is no likelihood of heavy rig coming on to the site. Incidentally after about 150 ft from this well there are 4 functioning wells in a row each separated by 40 ft and all of them drilled recently to similar specs but much shorter casing lengths and yielding continuously may be up to 3600 liters per hr. Our well is on a mildly downward gradient compared to these wells.
Dr. Pasha
sgap_drd@yahoo.co.in