IN a week which ended with the news that the Environment Protection Authority was investigating a third Hunter coal mine dam leak so far this year, it has been revealed that the environmental agency altered its licence agreement with AGL in the lead up to Christmas after a small tear and imperfections were found in the high density polyethylene linings of the South and North dams.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
The EPA has instructed AGL to now regularly review its safeguards at the three water storage dams on its Tiedmans property. AGL’s subsequent examination of the North dam last week has since identified a number of small holes and tears in the liner above the current waterline, estimated to be around 100.
The initial ‘imperfections’ were discovered during an EPA audit inspection on October 23. Acknowledging AGL’s statement that the water level in the South dam had been below the tear for the last two years, the EPA concluded “that the risk of harm from the low pressure leak was low to minimal.”
The EPA’s risk review of the tear in the South dam took into account its location about halfway up the dam wall, the size of the tear (approximately 3cm), the changing volumes of water stored, properties of the soil underneath, and the water makeup itself.
The concern about the integrity of the holding ponds at the Tiedmans site has led the EPA to alter its licensing requirement just before Christmas. AGL must complete a “thorough assessment of the three dams, to identify any weaknesses, holes or potential imperfections which might result in leaks or splits” and undertake any necessary works to ensure the liners are impermeable. It must also develop an ongoing inspection program to ensure any imperfections or holes noted in the future are identified and rectified as soon as practical.
AGL said in a statement that the tear had “previously come to AGL’s attention during a routine inspection and repairs to the liner were carried out within days”. It said it also raised the matter at the time with the Gloucester Dialogue and Community Consultative Committee.
“The South dam currently is empty, the North dam only holds low salinity rainwater and paddock runoff. The East dam, which is double lined and has a leak detection system, holds low salinity “blended water” (a diluted mixture of local river water and ‘produced water’ from gas exploration predating the current Waukivory Pilot). The blended water was used in the Irrigation trial to successfully grow crops, prior to the trial ceasing in April 2015,” AGL stated.
It added that AGL has five years of seepage detection data for its dams, “which shows there have been no seepage of water from the Tiedmans dams.”
It said the dams have not been used for the storage of flowback water from the Waukivory Pilot Project (this is currently being trucked to Queensland for disposal by a licensed waste contractor). It added that it does not have any current or future plans to store produced water in either the North or South Dam.
“There is no material harm to the environment, no evidence of leaks (from five years of seepage monitoring data) and no compromise to the integrity of the dams,” AGL’s spokesperson said, adding that detailed inspections and repairs are ongoing.
While the cause of the holes is under investigation, they are suspected to have been caused by hose fittings.
Timed to allow for two of the dams to be emptied for a thorough inspection of their synthetic linings, AGL must submit reports to the EPA at the end of this month, March and September 2016.
