DARFIELD WATER SUPPLY
Rig 393: Power Probe VTR9700
Objective: To enable Darfield township to be supported by groundwater supply alone rather than rely on historic river supply, which required onerous and costly treatment.
McMillan Drilling was engaged by Selwyn District Council to construct a new deep groundwater supply bore as part of an upgrade to the Darfield Township Municipal Water Supply. The bore was constructed to a depth of 245 meters below ground level. The client required 300mm diameter steel casing to be advanced to a minimum depth of 180m to enable a submersible pump to be set appropriate to the anticipated static water level and pumping level. A 400mm diameter temporary pre-collar casing was installed to ensure the target depth was achieved at the specified diameter and doubled as a conduit for the construction of a deep sanitary seal.
Water level measurements and quality samples were taken throughout the aquifer zones during drilling to ascertain and delineate any discrete aquifers. All water quality samples were recovered and analysed by McMillan Laboratories to ensure fast turnaround and compliance with IANZ certification.
To avoid the extensive use of costly stainless steel screen in marginal sections of the aquifer the screen was designed and adopted a combination of laser cut steel and wedgewire stainless steel screens. The design was verified by the Client’s nominated Engineer and successfully installed at a completed length of 56m. At the conclusion of screening, development and aquifer testing the well was shown to be one of the highest yielding municipal bores in the Selwyn District.