The testing of a new production water bore at VRX Silica’s (ASX: VRX) Arrowsmith North project, 270 kilometres north of Perth, has confirmed a reliable supply of water within specifications.
Western Drilling was contracted to drill and construct a test production bore and two monitoring bores (one deep and one shallow) onsite, as part of VRX’s application for a licence to use water from an underground source.
The bores have been built to specifications exceeding the minimal construction requirements for water bores in Australia, as specified by the Department of Water and Environmental Regulation.
The test production bore was screened in the confined Yarragadee Formation Unit A aquifer in the Dongara Basin, with the screens installed between 320 metres and 392m depth.
A 250 millimetre fibreglass reinforced pipe casing was cement-grouted to 300m depth to prevent ingress of water from other parts of the Formation or from the superficial aquifer.
The deep monitoring bore has a similar construction to the test production bore with the grouting and screening over similar intervals.
The shallow monitoring bore was screened from 18m to 30m in the aquifer.
Hydraulic parameters
Test pumping by Western Irrigation helped determine hydraulic parameters and specific yields for use in a H3 Hydrogeological Assessment computer model.
Initial multi-rate testing was carried out, with the highest rate of 32 litres per second (L/s) yielding a maximum drawdown of 6.12m.
A constant rate test was carried out at 30L/s for 33 hours for a maximum drawdown of 6.20m in the pumping bore, 2.71m in the deep observation bore and no movement in the shallow one.
Preliminary assessment of the constant rate test data indicated a transmissivity in excess of 900 cubic metres/d/m resulting in a hydraulic conductivity of more than 10m/d.
Controlled test pumping showed that the confined Yarragadee Formation Unit A aquifer is capable of yielding project requirements of 900,000 kilolitres per annum.
The test production bore has been constructed to yield in the order of 1.2 million kilolitres a year.
Analysis of water samples taken during test pumping confirmed it is of acceptable quality for use as process water in VRX’s proposed silica sand process plant.
Significant step
VRX managing director Bruce Maluish said the bore testing was another significant step in the development of Arrowsmith North.
“The production of high quality silica sand requires a reliable water supply and this bore more than meets our specification,” he said.
“Adequate testing has been completed to allow for us to apply for an abstraction licence from the deep Yarragadee Formation without affecting other users of the superficial water sources.”
VRX expects to begin Arrowsmith North’s six-month construction period in January.
