Uncovered Bore Wells and Rescuing Techniques
“To meet the ever-increasing demand for water for industrial, agricultural and commercial purposes, bore wells are dug. With the huge increase in activities, groundwater is not available at all places. This increases the number of borewells with which water is obtained from aquifers present in the lower surfaces of the ground”.
Most bore wells that are constructed for the pure of water extraction are found in areas where there is a human activity, and some of these are unsuccessful in yielding any groundwater. These bore wells are often left open which has been known to be hazardous to human life.
The mouths of these constructions are often covered only with polythene sacks or brittle blocks of cement, which are never adequate measures for sealing a potentially hazardous hole in the ground. Children of very tender age tend to fall into these open bore wells and get trapped.
India being an agrarian country, our farmers depend mainly on groundwater for irrigation. With increasing population, lesser land holdings and urbanisation, deeper borewells are dug for groundwater abstraction.
What is called a bore well?
A bore well is a well of 4 1/2″, to 12″ in diameter drilled into the earth for retrieving water. In this 4 1/2″ and 51/2″ Borewells are commonly for Domestic purposes while 6 1/2 and more are for Commercial / Industrial purposes.
A bore well is cased in the region of loose subsoil strata open in hard rock or crystalline rock. High-grade PVC pipes are used for Casing in bore wells. The depth of a bore well can vary from 150 feet to 1500 feet.
Borewells & tubewells are very similar. Both are vertically drilled wells, bored into an underground aquifer in the earth surface, to extract water for various purposes. The difference in the two lies in the type of casing used, the depth of this casing and the type of soil where they are drilled.
How to seal unused or defunct borewells?
Sealing defunct or unused borewells is essential to prevent contamination of groundwater. If left open, unused borewells can lead to rapid contamination of the groundwater as they allow contaminants directly into the aquifers.
Good quality clay materials can be used to seal the borewell using different methods after removing the casing pipe (details in the reference given at the end). In case it is not possible to take such measures, cover the borewell properly using a good cap or provide adequate earthen cover over a concrete or stone slab kept on the borewell.
Ensure not to allow entry of wastewater or any external material inside an unused borewell. Alternatively, unused or defunct borewells can be used as rainwater recharge wells after providing proper filter arrangements and intake arrangements around the well.
Methods of sealing the borewell in a step by step procedure:
All obstructions in the well shall be removed before commencing to seal the well.
The wellbore shall be filled to within 3 m (10 ft) of the good casing with alternating layers of 19 mm (3/4 in.) grade granular bentonite and clean coarse sand. The lower 10 m (33 ft) of wellbore shall be filled with granular bentonite.
The thickness of intermediate granular bentonite layers shall not be less than 1.5 m (5 ft), and the individual course sand layers shall not be more than 5 m (16 ft). To prevent bridging within the borehole, it is recommended that these elements be poured at a rate not to exceed 2 minutes per 22.7 kg (50 lb) bag, or that these materials be poured through a 51 mm (2 in.) orifice.
The upper portion of the well, consisting of a depth equal to the casing length plus 3 m (10 ft), shall be filled with granular bentonite only.
Well, casing and well screens should be removed. In removing the good casing, the casing shall be kept full of granular bentonite as the casing is being pulled. At all times it must be ensured that the granular bentonite is flowing unrestricted from the lower end of the casing; i.e., that bridging of the bentonite is not occurring within the casing.
If it is not possible to remove the good casing, it shall be sealed, as in Step 3 above, and its upper portion cut off to a minimum of 1 m (3 ft) below ground level. Granular bentonite shall be used to form a sealed cap at the wellhead.
The sealed well shall be covered to the ground surface with material suitable for the intended land use and graded to direct surface drainage away from the well.
What is the uncovered borewell rescuing technique?
To improve security and efficiency of piping networks in industrial units, continuous inspection, maintenance, cleaning and repairing of pipelines are strongly demanded because due to ageing problems, a lot of troubles like corrosion, cracks and mechanical damages are possible in pipes.
These operations are quite expensive, so robots prove an efficient solution in this situation. A robot is an intelligent, re-programmable and multifunctional manipulator designed to work in an inaccessible environment to do a variety of tasks which are laborious, threatened and risky.
The robots with the flexible structure are needed so that they can adapt themselves according to the pipeline parameters. The wheeled robots are simplest, energy-saving and best suited for use on prepared surfaces. These locomotion systems have the main chassis connected to a set of wheels through links and joints.
Along with pipeline inspection, the concept of rescuing the trapped child from the borehole is also implemented in the robot design. Since the water level is decreasing day by day so more people put ever-increasing demands on limited supplies.
“To fulfil the needs, bore wells are constructed, but these are usually left uncovered. Many innocent children without noticing the hole have trapped and lost their lives”.
What is the future scope of rescuing technology?
The project can further be improved by adding or modifying by the following features:
An additional feature of the airbag can be used to provide support underneath the child which prevents the child from falling further deep.
Oxygen sensor and oxygen supplier can be installed.
The smoke sensor can be added to sense the dangerous gases concentration inside the pipe.
It can also be made waterproof.