Dear Experts
I am writing to seek the advice & suggestions of experts in retrieving my failed borewell. I have provided a detailed overview of my experience at https://www.indiawaterportal.org/ask/12636. A synopsis of the same is listed below
· Location: Near Tenkasi, Tirunelveli District, Tamil Nadu
· Foothills of the Western Ghats, I share a common boundary with the Western Ghats, the elevation of the mountains commences from the Northern boundary of our farm
· Slopy terrain [gentle slope] from North to South, Extent of Slope from North to South – Approximately 15 Metres from highest to lowest point, spread over a distance of 620 metres
· Ground Water survey carried out by the Geologist using an Electrostatic meter indicated good water potential at a depth of 150 feet
· The borewell was drilled in the lowest point in the field
· Hit hard rock at 63 feet and outer casing lodged at 63 feet
· Borewell drilled to a depth of 450 feet
· Water struck at 90 feet and we had very good force sufficient for a 2 inch pipe output between 110 feet to 150 feet; Drilling carried beyond 150 feet based on driller’s advice; dwindling water between 150 to 190 feet; beyond 190 feet till 450 feet we did not encounter water, and we just keep getting grey rock powder
· We hit a single rock at 63 feet and kept going till 450 feet
· Borewell drilling data
o Upto 10 feet – Laterite with clay
o 10 TO 18 feet – Red Soil
o 18 – 30 feet – Highly weathered rock
o 30 – 40 feet – Weathered rock
o 40 - 50 feet – Boulders
o 50 – 120 feet – Jointed gneiss
· Post drilling test carried out through hiring of a 5 HP motor and using an Air Compressor to check availability of water. There was no water despite trying to pump using the Air Compressor
· We now realise that this is a locality where water is available at lower depths around 150 feet
I would like to seek the advice of experts in this forum for retrieval of this borewell and my queries are listed below;
1. There was sufficient water between 110 to 150 feet, where has this water gone?
a. Is the water lost to possible dry fracture openings between 150 / 190 feet downwards? I can confirm that from 190 feet onwards there was there was hardly any change in the rock layer, with a marginal change at around 400 feet]?
b. Is there a possibility of us having hit a soft rock which is resulting in water seepage through this layer?
2. Given that we hit water between 110 to 150 feet, is there merit in sealing / closing the borewell 150 feet or 190 feet downwards, and If yes, How should we seal it at a particular depth?
3. There were also some suggestions on pulling out the PVC Pipe casing laid to the depth of 63 feet and creating slots in the pipe to capture potential surface level water and pushing the PVC pipe back. But I do not see merit in it as there was no water struck till 90 feet. Do the experts agree with my views of not pulling out the PVC pipe?
4. On a different note, I would like to know about hydro fracturing, Is Hydro Fracturing relevant only for existing fractures or to create new fractures?
5. I also read about creating rain water harvesting around the borewell to recharge the ground water and increase yield in my borewell. If yes, how can I create rainwater harvesting around the borewell, what should be the diameter and what should be the depth, and how do I create a rain water harvesting structure?
This is a long message with several questions. I shall appreciate the advice and suggestions of the experts in this forum
I look forward to hearing from you
Kind regards
KRISHNAN P S
CHENNAI