Even as the death of a four-year-old girl, Mahi, who was trapped for 86 hours in a borewell in Gurgaon has shaken the collective conscience, such tragedies in the State are unlikely, given that the average diameter of borewells is too small for any child to fall through.

Officials who supervise digging of borewells for public water supply system say that on an average the diameter of the wells is barely six inches. Normally, in a hard rock terrain, the work is completed in eight to 10 hours. Even in the case of sedimentary formation where the duration of work goes on for 15-20 days, the site is under constant vigil and usually, it is about a km from any habitation.

Given the trend of declining groundwater table in cities and towns, the borewell phenomenon is restricted to rural areas, the officials add.

Borewells in and around Chennai have a maximum diameter of 4–6 inches. They have casing pipes that jut at least 2 feet above the ground level. Following an incident in north Chennai many years ago, when a child fell into a borewell located on a street, the State government passed an order, directing closure of disused borewells. Since then, there were no reports of any mishap.

Borewell agencies say pipe casings are sunk immediately on drilling the holes, which are never left open. In failed cases, the holes are closed immediately with gravel and sand.

However, experience has shown that even the most unlikely event cannot be ruled out. About three months ago in Madurai 10 persons, including women and children, were killed when a passenger van fell into a deep open well near Thirumangalam. Jolted into action, the district administration and the police department launched a joint survey to identify open wells and ordered the construction of barrier walls or closure of dysfunctional ones. Also, the practice of rig operators orally informing the authorities in advance about their plans is no longer in vogue, an engineer of Tiruchi Corporation points out. Deputy Director (Fire and Rescue Services Department, Southern Region, Madurai) M. Shahul Hameed suggests preventive steps, such as cautioning parents to be vigilant whenever a borewell is being dug in their neighbourhood. Borewell operators or contractors should also ensure that the area is adequately kept guarded round the clock till the works are completed. The borewell should be temporarily covered as a protective measure, as strangers may be unaware while crossing the point.

L. Elango, professor, department of Geology, Anna University, says that not just borewells, there is a need to ensure that large open wells in agricultural areas have parapet walls.