We drilled a borewell in JP Nagar I Phase, Bangalore about 3 weeks ago. The first experiment failed as the soft mud around collapsed repeatedly, the 10" PVC casing could not be pushed in properly.
Then we moved to a new spot 4 feet away and used a rotary slow driller. They hit rock base at 85ft. They also inserted 3mm MS casing till the rock bed and left. The power driller came back and drilled through the rock bed. They were now able to push the MS till 115 feet. This seemed a bit strange to me, as the rotary driller had already pushed in the MS pipe, the big rig could only use smaller bit to go through that drill. How could they manage push through ?
Next we stuck water source at 120 feet (1"), again at 180 feet (2") and finally at 220 feet we hit 3", we went up to 240 feet and stopped.
A week later when the pump installer came down, they could lower the submersible below 120 feet!
Hence we ordered wash by another driller.
He washed and the water was completely muddy. With in 30 mins the bore was filling with silt again, another was was attempted with in an hour and they left.
Their version is, the casing is not seated properly or the below the first rock formation there is a silt layer, lots of pebbles etc.
I personally lowered a weighted nylon rope and again the weight (a heavy lock) would not go below 130 feet.
Second driller claims that in these areas, MS should have been put in till 145 feet atleast. But I have personally seen that the big rig could not push the MS any further.
1) What can be done to save this bore ?
2) Does really silt fill up that fast ?
3) Can slotted pipes be used in this bore ?
Manu,
manukreddy@yahoo.com