We have dug a bore well in II-Main, I-Block, BEL-Layout, Vidyaranyapura Bangalore North on 13th July 2009. The bore was drilled up to 158 feet where the driller found boulders and silts (Quartz pebbles of 0.75 inches to 1.5 inches with sandy slurry and rock powder in black color) and stopped drilling further. He inserted the 6.5 inches MS casing up to 142 feet and later inserted 10 inch Outer PVC pipe up to 150 feet. Gave a report of min. 2.5 inches of water for life and gone.
Next day a submersible pump of 1.5 hp was installed at a depth of 130 feet and checked for the water discharge. The discharge was only 100 LPM for 10 minutes and quality of water was muddy for 2 min and 80% clear water for 8 min. was noticed. The matter was reported to bore well company. After persuasion the company came with low pressure 6 inch rig to flush the cavity up to 158 feet and insert 4.5 inches slotted inner PVC pipe to arrest mud entry in to cavity. But the II-Driller could flush the cavity only up to 8 feet and inserted 4.5 inch slotted inner PVC pipe up to 150 feet, leaving a bare bore of 8 feet. There was a danger of the silt and pebbles reappearing from bare bore and enter the slotted pipe from bottom.
Immediately after insertion of slotted pipe the pump was reinstalled at 135 feet and checked for the volume and quality of water. The discharge was 100 LPM for 30 minutes and quality of water was muddy for 3 min and 80% clear water for 27 min. was noticed. However in between the muddy water was coming and was getting cleared. On 4th day the HDPE pipe end was prepared and the pump was re-installed at a depth of 137 feet. On switching on the motor, the pump ran for about 2 minutes and suddenly, the inner slotted pipe along with pump came up by about 12 feet from the ground level with full force. The pump was removed and measured the depth of bore.
The depth was only 105 feet. Another 53 feet is filled with silt and pebbles. The matter was reported to company and there is no response. The static water level is about 12 feet from ground level. My question is, Is it possible to clear the bore up to 158 feet and drill further until rocky surface is reached and push the MS casing pipe till rocky surface to enable further drilling. The driller is claiming not possible. I have already spent Rs. 1.27 lakhs for this. I am herewith attaching the detailed report of the bore. Please suggest. Can you please send the procedure to be followed to drill bore well in boulder and sand prone area.
Somaraju
somarajug@gmail.com