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Correct way to close borewells

I am working for an NGO called 'Water Harvest' in the bioregion of Auroville, Tamil Nadu. We have an ongoing project about closing a 100 or more borewells drilled up to 150 metres depth. My question is: How do we close the borewells correctly and prevent intrusions of surface water and other sources of pollution?

Any help is appreciated!

Regards

Jos Eisberg

joseisberg@arcor.de

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Comments

1.

As unused/abandoned wells pose great threat to human/animal safety and cause severe groundwater pollution, most developed countries not only have laws for their scientific sealing to restore the original geological conditions prevailing before their construction but also make available grants and expertise for taking up the work.

India has millions of such unused/abandoned wells used once for drinking, irrigation and industrial use. In the absence of laws for their scientific sealing, they continue to remain there for use as sanitary sinks and cause enormous harm of irreperable nature particularly to groundwater quality.

Even educated people do not understand that such wells contaminate their own nearby wells used for drinking and other purposes. While working for an industry facing groundwater-quality problems, it took us a long time to convince that the deterioration of groundwater quality is because of the existence of certain nearby unused/abandoned wells. After great persuasion, we could convince them for granting funds to seal those abandoned wells and thereby improve the overall groundwater quality.

Under this scenario, it is gratifying to know from Jos Eisberg that his NGO, "Water Harvest" got funds to take up the gigantic task of permanently sealing over 100 unused/abandoned bore wells of 150-metre depth in the Auroville bioregion.

I suggest Jos Eisberg to make a google search for "sealing abandoned wells" to get a wealth of information of great value on the latest methods used particularly in North America to seal abandoned wells. He can then evolve a methodology best suited to the prevailing geological conditions of the Auroville bioregion where artesian groundwater occurs in Upper Cretaceous sandstones.

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

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

2.

Dear Member,
This definitely is a great gesture and will do alot to the communities/habitats around and avert ground water pollution. Get a complete detailed mapping done and have some inferences on the geo-matrix and sub-soil water levels etc.Local augers can also be contacted to give you an idea of the stratas of soil beneath.
For bores witjin 200mm , you mention 150 mtr. is it. use good quality clayey-soil with some stone aggregate and use it as a plug to create an imperviuos media all through to the bottom... and on top a cap of distict colur with a signboard.
With well wishes from Ajit Seshadri
ajit.seshadri@vigyanvijay.org

Er. Ajit Seshadri,Head- Environment, The Vigyan Vijay Foundation

3.

In the coastal area a deep borewell passes through different aquifers salaine and fresh aquifers till a high yielding zone is tapped. Due to corrosion or leakage in casing pipe the top saline water will intrude the fresh water aquifer and by this process two aquifers may get connected and a fresh layer may turn saline after some years. So it is highly necessary to back fill it with Concrete mixture by compacting till it reaches the ground level.

Sibasis Panda

sibasis Panda

4.

I am also with an NGO based in Jaipur Rajasthan and basically a hydro geologist. Abandoned bore wells need to be refilled with proper materials till the previous layers are reached and fully blocked. This is a site specific requirement and if we have modern tools we can go for loggers or ascertain soil and rock characteristics otherwise and then plan for material resources. It will certainly need gravels, cobbles, pebbles, soil and cement mixtures depending upon the site needs.

5.

Dear Sir, Mr.Jos Eisberg,

The concern for finding a proper way to seal the old abondoned bore wells is very much appriciated. Great many violations of misusing abondoned or unused bore wells are causually going on just like that in Industrial(effuluent disposal with high pressure) & municipality(debris dumping) areas and in coastal areas(inviting cross border terrorism of SEA WATER intrusions) with out knowing or just ignoring the impact over the soil,nature, Ground Water and Community.

THE PROPER WAY IS BY CONDUCTING NATURAL gamma LOGGING in the old borewell. The area under reference is a sedimentary formation. Generally Sub Artisan condition prevails in The ground water acquifer in the (CUDDALORE) sandstone formations. A clear delineation of impervious(Clay) layer and the saturated aquifer can be easily interpreted from the NATURAL GAMMA LOGGING chart.The portion of the Bore well between the ground level and the Impervious layer should be back filled with dried clay balls or with cement concrete.

This is possible only when the bore well not totally silted up, atleast up to the Impervious formation. In case of silted up bore wells, by using bailing method the bore should be cleared upto the clay layer (with previous drilling history of the surrounding area) and then backfill with dried clay balls or with cement concrete. Compressure development should not be done to clean the bore well. Which will totally damage the PVC casing and the slotted portions.

With regards.
ramachandran.paeriasamy@gmail.com
9843140359

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