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Low yielding borewell in C.V Raman Nagar, Bangalore - Solutions?
Submitted by srimash on March 21, 2011 - 00:58
We dug a borewell in March, 2011 on a 50X40 vacant residential site in C.V Raman Nagar. The following data was given to us by the borewell drilling company on completion of drilling & they told us that the well was low yielding but we would still be able to pump 1500-2000 litres in 1 hour in the morning & another 1500-2000 litres for 1 hour in the evening. During the drilling, we struck rock at 84 ft & after 320 ft there was some moisture in the discharged sand all the way upto 820 ft. We drilled upto 820 ft because that was the water level depth in & around that area based on enquiries & recommended by the diviner.
Total well depth drilled - 820 ft
Water struck at depth of - 120 ft , 320 ft
Total yield - 3/4 inches
Soil condition - Boulders & Silt
Recommended to use 2HP Air Compressor pump
After 4 days , we checked the water level in the well using a video camera. We went in for the camera test because the pump test is not yet possible on the site as we don't have temporary power connection yet & we were fairly desperate to atleast see the water after spending 1.5 lacs on the well. The camera hit water at 255 ft, which means that there was (820 ft - 255 ft) = 565ft of water column inside the well. The camera report confirms fractures at 200, 260, 265, 300, 375, 392, 480, 505 & 792 ft. We could see water flowing alongside the side of the well at 120 ft & once the camera entered the water, there were bubbles & ripples in many places which the camera crew pointed out as micro water sources.
Overall the camera crew recommended that we could go for submersible pump with auto level controller as there was sufficient water. They also recommended that we install a filter pipe before installing the pump as there were multiple loose rocks inside the well.
My questions to the experts are as follows-:
(1) Given that the water level rose to 565 ft from the bottom of the well in 4 days - is the water yield actually more than the 0.75 inches that was initially stated by the drilling company ?
(2) Should we go in for the submersible pump as recommended by the camera crew or compressor pump as recommended by the drilling company ? There is only 5 ft of silt at the bottom of the well. We were able to take the camera down upto 815 ft.
(3) We drilled the well in March, which is basically after 6 months of dry weather in Bangalore. Is the yield likely to improve after the monsoon, which is July - Sept in Bangalore ?
(4) Is the yield likely to improve if we collect the rainwater from the open terrace catchment & channelize into the borewell ?
(5) Is the filter pipe a must ?
Thank you in advance for responding to my questions
Comments
1. Low yielding borewell
Dear Srimash,
The answers to your questions as I visualize it are as follows-:
(1) Given that the water level rose to 565 ft from the bottom of the well in 4 days - is the water yield actually more than the 0.75 inches that was initially stated by the drilling company ?
Ans: 0.75 inches is equivalent to 400 liters per hour, Rise in water level of 565ft from the bottom is indicative of only about 3000 liters of water ( standing water column) . so this really does not indicate anything positive.
There is a possibility that water is moving out at a faster rate as compared to the inflow in to the well. other wise the water level should have risin way above the level where you first encountered water - i.e. 120ft.
(2) Should we go in for the submersible pump as recommended by the camera crew or compressor pump as recommended by the drilling company ? There is only 5 ft of silt at the bottom of the well. We were able to take the camera down upto 815 ft.
Ans: You could install a submersible pump as suggested, but it will involve higher costs, especially the screen to ensure that the borewell walls do not colapse.
(3) We drilled the well in March, which is basically after 6 months of dry weather in Bangalore. Is the yield likely to improve after the monsoon, which is July - Sept in Bangalore ?
Ans: probably the yield would increase once the well is properly developed and the openings- joints fractures etc connected to the aquifer openup with the material in between the openings moving into the borewell area along with the water.
(4) Is the yield likely to improve if we collect the rainwater from the open terrace catchment & channelize into the borewell ?
Ans: You could always hope for that to happen, even though it may benifit you only during the monsoon seasons, but then as you are removing water from the ground, it would help if you recharge the system as well. But please ensure that you take proper precautions while desigining the filter etc, or you will land up contaminating the system.
(5) Is the filter pipe a must ?
Ans: if the camera images show presence of joints and fractures, there is always a possibility of these falling into the borewell and the pump getting jamed due to it, and to prevent somethign like that from happning a filter pipe with gravel filter aroudn it is always the ideal thing to do. or opt for a aircompressor pump, which has not expensive moving parts in lowered in the borewell.
Hopefully this answers your questions.
All the Best
Dr. Anil Lalwani
www.wellwaterworks.com
Thank you in advance for responding to my questions
2. Dear Dr. Lalwani, Thank you
Dear Dr. Lalwani, Thank you for your prompt response. We enquired about the cost of the filter pipe & it is Rs.120/ft, which is nearly another Rs.85,000 cost. We will go with the air compressor pump as recommended by you with rain water recharging through a filter pit. Thank you once again for the very valuable feedback.
3. Low yielding borewell in C.V Raman Nagar, Bangalore - Solutions?
Dear Srimash,
To enhance water yield in a borewell, no other method other than hydofracturing is dependable.
For this, first investigate the borewell using a borehole camera. ( Though you have done it already, if the video of the sasme is not available, once again it must be done.)
Then, if fracturing is feasible, fracture the borehole & conduct pumping test. If water is plenty, no need of placing perforated inner casing pipe.
Otherwise it should be used before lowering pump.
For further details and execution of hydrofracturing, pl. call.
Neeradhan
Geologist
09447087293.
4. Dear Neeradhan, Thank you for
Dear Neeradhan, Thank you for your response. I have heard that hydrofracturing is a costly affair. Any idea how much this is likely to cost ? Also, is it possible to do hydrofracturing at a later stage, once the house is built ? The borehole is located in the 16X9 car porch area of the 50X40 plot.
5. Hydrofracturing
HF costs around 25000. It is difficult if the ceiling of your porch is RCC. If it is sheet, no problem at any time.
6. Dewatering borehole system
Hi all,
I have heard that dewatering borehole system is a new technology in India. I want to know if it is feasible to use the technology for residential purposes.
Can I please have further information on this technology, the cost involved and who are the experts in Bangalore who can be entrusted with this work.
I am just about to start drilling a bore. So your quick reply would be very much appreciated.
Thank you
7. Low yielding borewell in Bangalore-In desperate need of advise
We dug a borewell on 17th March 2012 on a vacant plot of 30 x 40 at BDA Layout, BSK V Stage, Uttarahalli, Bangalore. The digging was stopped at 863 ft. as there was no noticeable water strikes (as the dust suggested that it was a huge single rock till 863 ft., and there was little noticeable moisture in the dust produced). MS pipe was inserted upto 32 ft.
On completion of drilling, the borewell company official told me that we might have got water of about 1/2 " sufficient for a family of 5. After 2 days of digging, we tried to measure the depth of water and depth of borewell. First we dropped a small stone into the well, and it struck water within 24 seconds. By multiplying it with 9.8, we assumed water depth at 235.2 metres i.e. at 771.5 ft.
Then we took up rope test by tying a small stone to one end of the rope and inserting into the borehole. This could not be completed properly due to the following: The stone tied into one end of the rope hit the depth of the borewell, after which we tried to pull back the rope to test the depth. However, about 25 ft. of rope right from the end where the stone was tied, came out full of oil. It may be due to the oil used by the borewell digger, which has entered the well and settled above the water. Hence, this test of ours failed, and we could not do much here.
Today, after 4 days, we again conducted the exercise of dropping the stone, and it took 18 seconds for striking the water level. By this we assumed water depth at 176.4 metres i.e. 578.59 ft.
With the above details, can any water/borewell expert clarify the following :
1. Do I have enough water in the borewell for a family of 5 i.e. atleast 1/2 "of water?
2. What is the process of removing oil from the borewell and whom should I contact for the same in Bangalore?
3. Can I engage borehole camera test to verify the water fissures? If possible, whom should I contact for such test in Bangalore?
4. What type of motor is to be used for pumping the water and the frequency of pumping?
I am very desperate in getting proper help in this matter as I have already spent about 1.2 lakhs for digging the borewell.
Please respond.
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