AGL says sampling carried out between July 1 and December 31 last year has shown ground and surface water quality on its Tiedmans property south of Gloucester remains unchanged.
The company said the testing showed there had been improvements to soil quality on the property since an irrigation trial using produced water from gas wells blended with fresh water first began in April 2013.
“Independent water experts, Parsons Brinckerhoff, concluded the blended water (produced water from deep coal seams combined with fresh water) complied with the Australian New Zealand Environmental Conservation Council (ANZECC) irrigation guidelines and was suitable for irrigation,” an AGL spokeswoman said.
“Soil and crop analysts, Fodder King, reported that the soil in the irrigation trial area showed significant improvement due to the work done to prepare the ground for the winter and summer crops in 2013.”
“Due to drier conditions, there was a slight increase in salinity within the upper soil layers, however, Fodder King found no indication of adverse effects from the irrigation of blended water.”
The first crop sown on the Tiedmans property (triticale) and irrigated with the blended water was harvested and sold to local farmers in November last year. The Environmental Protection Agency (EPA) reported its concerns over the trial in early 2013 but the State government chose to keep the report confidential.
In its report, the EPA said the project was high risk and was likely to produce dangerously high salt levels.
It also warned of damaging effects to local wildlife.
“This data shows that blending water from coal seams with fresh water for irrigation can be done effectively. The results are clear - surface water quality remains unchanged and the soil is improving,” said AGL’s hydrogeology manager John Ross.
“AGL will continue to monitor the soil closely as there has been substantial rain since the start of the year and salt is expected to move lower into the soil and weathered rock.
A separate report by Parsons Brinckerhoff using the latest water dating technology found that the salty water in the Gloucester Basin’s deep coal seams is in excess of 300,000 years old.
“Groundwater moves incredibly slowly, and in this case, probably less than a centimetre per year.
“Given the location of the wells that were sampled, we suspect the water flows from east to west towards the centre of the Gloucester Basin,” Mr Ross said.
The latest irrigation trial results have been published on the AGL website.