Borings for observation wells, are normally sealed With an impervious cap near t

ID: 1827958 • Letter: B

Question

Borings for observation wells, are normally sealed

With an impervious cap near the ground surface. This cap prevents significant quantities

Of surface water from seeping into the well. For convenience, manufacturers supply a

Pelletized clay that has been dried and formed into 10-mm diameter balls. The driller then

Pours these balls into the boring and adds water. As the clay absorbs the water, it expands

and seals the boring. What type of clay would be most appropriate for this purpose? Why?

Would other clays produce less satisfactory results? Why?

sodium bentonite is a good option for such purposes which absorbs water and expands providing sufficient sealing.

Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite.

It is due to this property of bentonite that it is superior over other clays and gives enhanced performance in case of sealing

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