The Century Orchards site has existing bores accessing the Murray Group Limestone at a depth of 130m, one of which will be used as the source for the desalination plant. However, for the reinjection scheme to work, boreholes are also needed in the Loxton Sands aquifer for the brine discharge. The cost of drilling varies depending on the depth, required diameter, the composition of the site (e.g., rock layers can increase costs), borehole requirements such as screening, and other factors such as accommodation. As such, drilling can cost in the order of several hundred dollars per metre.

A well construction permit was obtained from DEW, and we are grateful that Clear Water Drilling Services were available to undertake the drilling. Drilling commenced on 17 June for two reinjection boreholes and took one week to complete. The first borehole is near the production borehole to minimise pipe length and the second is located approximately 150m away to give additional capacity and some built-in redundancy. The boreholes were constructed using a mud drilling technique and encountered a coarse sand, which is good because coarser sediments generally have a greater porosity and ability to transmit water. The depth of the boreholes depends on the depth to the clay layer. For the first borehole this was 22m and for the second borehole the depth was 18m. Because these bores were constructed to discharge water to the aquifer, long screen lengths of 12m and 9m were used.

With borehole drilling complete it is possible to install the desalination unit with hydraulic and electrical services needed to connect all components. This project would not be possible without the support of the South Australian Department for Environment and Water, who were able to give advice on the establishment of this scheme, and for their approval of the drilling permit. Also, seeing the skills of Clearwater Drilling in action was fascinating, to be able to use a novel casing approach and for precision and professionalism in establishing the boreholes.