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Rocky Layer in Borewell - Cause for Concern? Andhra Pradesh

We constructed a bore well in Kuppam, Chittoor district, Andhra Pradesh. The characteristics of the well are as below.

Diameter of the bore well: 6.5 in

Depth of the borewell: 550ft

Casing used: pvc casing 30 ft

Date of construction:May 7th 2009

From 30 to 550ft the presence of a continous rocky layer was see, And water source obtained from 200 to 490 ft. I am planning to install a motor soon. Some doubts regarding the same are:

1. Does the presence of an extended rocky layer affect the performace of the well or yield / life?

2. Are there any precautions that I can undertake at present to ensure the long life of the well?

M.R.Prasad

prasadrp@gmail.com

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Comments

1.

Dear Sir,

The presence of rock does not affect the performance of the yield. Since you got water below 200 fet up to 490 feet.

Do you mean long life as the continuous supply form the bore well. For this you may kindly carry out rain water recharge by just making the running rain water walk or sit. Dig minor pits and convert them into chock pits and retard the running speed with breakers.

With best wishes,

A. Raja Mohamed
Geophysicist
Coastal Energy Private Limited
Chennai - 600 006
bismi1234786@gmail.com 09443619352

A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352

2.

Dear Prasad,

From your description, it is clear that soft formation requiring casing occurs up to a depth of 30 feet and hard rock requiring no casing beyond that depth. The web page at http://www.indiawaterportal.org/blog/wp-content/uploads/2008/03/deepgw.jpg shows how groundwater occurs in hard rocks within pipeline-like water-bearing fractures extending from the surface to the underground. In your well, the hard rock between 30 and 200 feet and between 490 and 550 feet is devoid of any water-bearing fractures. You can know from the driller the depths at which these water-bearing fractures occur in your bore well. With progress in drilling, more water-bearing fractures must have contributed water to the bore well and thereby increase its yield gradually. Although you have not mentioned the yield expected from the bore well, you appear to be satisfied with the yield.

The driller must have properly cased your bore well with good quality PVC pipe by making it snugly fit into the hard rock with no scope for any loose material to enter into the bore well. As formation against the uncased portion is hard rock devoid of any loose formation, there is no scope for any loose material to enter into the bore well from the surface or sides or the bore well.

You should be happy that you have got an extended rocky layer in your bore well that ensures long life to your bore well without the need to take up any precautions.

Good luck.

Dr. R. Jagadiswara Rao
Retired Professor of Geology
Sri Venkateswara University
Tirupati, AP 517502
(Presently on a visit to Canada)
rjagadiswara@gmail.com

Dr. R. Jagadiswara Rao, Professor of Geology Retired, Sri Venkateswara University, Tirupati, AP 517502, India rjagadiswara@gmail.com

3.

Dear M.R.Prasad,

There is no problem with the rocky formation. The well can be utilizing for pumping for domestic need. Only precaution is to ensure the lowering of pump at suitable depth so that it takes into account the drawdown.

Thanks,

D. Chakraborty
Scientist
Central Ground Water Authority (CGWA)
New Delhi

4.

Dear all,

Many thanks for your reply, sorry for late reply, your answer helps a lot,

i will suggest many of my friends to use this portal in order to solve their water problem.

thanks

prasad

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