The University of Canterbury air conditioning project consisted of constructing a 300NB abstraction bore to a depth of 200mbgl and two 300NB re-injection bores to 60mbgl. The positioning of the bores close to large multi-storey buildings, the presence of artesian aquifers, stringent environmental conditions and university activities required careful consideration. Precautions included installing pre-collars to isolate foundation vibrations during drilling and pressure grouting at depth to contain the potentially high artesian and re-injection pressures. Rotary and Cable Tool methods were adopted for this project given the site constraints and potential for above-ground artesian aquifers.

Considerable attention was placed on the removal of discoloured water during the construction phase and the contract allowed for 1000m³ of water to be transported off-site at considerable expense. To avoid this cost, we successfully constructed and operated a temporary 300m³ settlement and filter tank system to treat all water prior to discharge into Okeover Stream, negating the need for off-site disposal.

The contract was completed during the University Christmas vacation, on time and on budget. The abstraction bore now delivers cool water (approx. 14°C) from a deep aquifer to the air conditioning plant prior to re-injection into a shallow aquifer via the re-injection bores.