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Pump Stuck - Borewell with multiple issues - Technical Advice Required! Whitefield, Bangalore

Hello All,

 

I stay in Whitefield areas, Bangalore. We dug a borewell ten days back. I hired a driller through JR borewell and showed the point myself based on convenience as there weren't much options. The driller never gave me a report. so please try to evaluate based on the information given.

PVC casing upto 23ft

MS Casing upto 85ft

Water flowed out of the borewell during drilling at a depth of 420ft. 1.5 " per driller. I asked them to continue upto 700ft as one of my engineer said that a second aquifer would make the source reliable but we didn't find any other source as far as i know.

 

I fixed in a 3HP single phase texmo pump at a depth of 650 ft. Intially pump was never able to pull water continuously but a pause of 5 mins kept the pump running with full capacity for 30 mins. But the water would slowly reduce in 30 mins. It pumped put approx 10000 litres for two days. The third day only air was coming out and that too only for a couple of secs. After that no action. The pump installer decided to pull out the pump and check but in vain. Ten different people gave ten different suggestion. So i decided to scan the borewell. The video camera couldn't proceed beyond 310 ft. Suprisinly we saw another water source at 250 ft with water gushing out from the wall. I would say that was approx 1 inch water gushing out. There was another guy with the camera fellow who was suggesting a jerking at that source with a 100% guarantee of increased yield but i had other concerns.

 

Water level is at around 260ft. The other interesting fact is that water doesn't stay in the borewell i.e. it flows through some other hole. i tried to fill it with a tanker with no success.

 

So my questions are -

1) what has filled upto 310ft. A reliable source(geologist) says that no silt exists in Whitefield area while the driller and all others claim that silt has filled in upto 310ft.

2) what should be my next course of action ? I hired a compressor with no success. he says that air pushed is leaking out of the hole.

3) Is it a good option to abandon the pump, ignore the source at 420 ft and depend on the one at 250ft ? Somehow block the borewell at 350 ft so that water level may rise upto 100ft, lay a new pump at 350 ft and run it at timed intervals. If so what are the methods to clean upto 350 ft and block the borewell beyond that ?

4) If it is indeed silt, how can we clean it ? If cleaned would slotted PVC pipes fix the problem ? What is the silt enters through the slots ?

 

 All I know is we struck rock at 85ft and it was hard rock all the way.

Kindly advice on further action required to rehabilitate the well.

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Comments

1. Borewell with multiple issues - Technical Advice Required

Dear Murali,


After having gone through what you have described about your borewell, and giving it some thought I have tried to answer your questions based on what I imagine the situation to be and what could be done to salvage the borewell.


1)      What has filled upto 310ft. A reliable source (geologist) says that no silt exists in Whitefield area while the driller and all others claim that silt has filled in upto 310ft.


ANS.  It may not be silt, but clay that you may have struck and due to swelling when it comes in contact with water it has slowly risen to this present level.


2)      What should be my next course of action? I hired a compressor with no success. he says that air pushed is leaking out of the hole.


Ans. Had you posted your problem earlier I would have told you that using a plain compressor will not work. Reason is that you have water commignnin at 250ft but water level does not rise beyond 260ft, this means that at 260 ft it is moving out of the borewell and where there is place for water to move out there is definitely going to be place for ari to move out.


 


If you are not worried about damaging the pump a bit, I would suggest that you try passign air through the delivery pipe of the pump itself, this may help in atleast dislodging the pump and you may be able to pull it out.


 


For getting the rest of the material out once this is done -


What you could do is use a pipe in pipe assembly and first lower a bigger diameter pipe say 1.5 inches diameter till the base where it gets firmly lodged in the material below. Then in this pipe lower a 0.5 inch pipe and pass air through the 0,5 inch pipe, this will ensure that there is no loss of air and your well will get cleaned.


 


But you must keep in mind that this will be a slow  and difficult process , and both the pipes need to be lowered continously. Secondly keep this in mind that there are chances that the borewell could get filled up once again.


3)      Is it a good option to abandon the pump, ignore the source at 420 ft and depend on the one at 250ft? Somehow block the borewell at 350 ft so that water level may rise upto 100ft, lay a new pump at 350 ft and run it at timed intervals. If so what are the methods to clean upto 350 ft and block the borewell beyond that?


Ans. If  the pump does not come out  you will have to consider this option, but as you say there is a source at 250ft, this can e utilized, and anyway the source at 420ft may not be acessiable due to the borehole fillign up once again.


 


I doubt that your water level will rise to 100ft, the fact it is not rising above 260ft itself implies that around that level there is some sort of outwards flow. From the borewell. If you can manage to plug this outflow then probably you could  get the watr level to rise a bit but then too not as high as  100ft .


 


If you want to block this place you will have to use cement- an seal of the outflow- something similar to what is done in the petroleum industries. After fillign the borehole with cement to the desired level, one needs to redrill the center of the well with a slightly smaller diameter  hence if you have a 6 inc borewell at present then you could drill a 4.5 in borewell after cementing the well, but if you have a 4.5 inch well then the job will be difficult to achive. 


4)      If it is indeed silt, how can we clean it? –


This part has been discussed in your question 2.


 


If cleaned would slotted PVC pipes fix the problem? What is the silt enters through the slots?


 


Ans. Just having slotted PVC will not help, you will have to plug the PVC pipe at the base and  place a gravel filter pack around the slotted pipes, but again it is not an easy job.


Your request - Kindly advice on further action required to rehabilitate the well.


 


I would ideally suggest that you install a compressor pump, hence no costly equipment is inside the borewell and there will be no damage to any moving parts of the pump, and lower this assembly to whatever depth possible.


 


If you are keen on opting for a submersible pump, I will first advise you to pour in some ammount of  pebbel mayy be a gunny sack or two  full just to ensure that atleast 5-10 ft of the borewell is filled up by it this would ensure that it keeps the material from bottom form rising upwards.


 


And then lower the submersible pump till the bottom. But you will probably get only 50 ft of water column and hence the pump will have to be throttled and the discharge mached with the inflow in to the well.


 I hope this will help you in finding the best option to move forward with.


 


Regards,


Dr. Anil Lalwani


www.wellwaterworks.com


 




2. Liked the idea of clay

Liked the idea of clay getting filled up when contacting water. To plug the hole at 260, you can use the casing pipes.

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