Expert panel raises concerns about Santos coal seam gas impacts

A Santos plan to develop coal seam gas in northern NSW has been found by an independent expert panel to lack key data that potentially underestimates impacts on threatened ecosystems and ground and surface water.

The report by the Independent Expert Scientific Committee, released without fanfare last month, identified “knowledge gaps, uncertainties and data limitations” within the Environmental Impact Statement submitted by the energy company for the $1 billion-plus Narrabri project.

Controversial CSG wastewater ponds

An aerial view of the wastewater treatment plant at the Santos coal seam gas plant in Leewood, north-western NSW.

Among those gaps is the question of just how much wastewater the planned 850 CSG wells will extract and the wider impact on groundwater. The experts had “low confidence in the water balance modelling” provided by Santos. 

“Contingency actions are not provided to address the possibility of excess water storage if other beneficial reuse options [such as for irrigation] are not available,” the panel’s report said.

Other issues include the possibility the drawdown of water may exceed a two-metre threshold in some areas, potentially affecting farmers and groundwater-dependent ecosystems (GDE).

The project should also justify why its groundwater model excluded the possibility of faulting in the geological structures as the water is removed, reducing pressure.

The experts also found fault with Santos’s assessment that there were no so-called type 1 GDEs, saying it was “based on very limited field sampling”.

Those ecosystems it did identify were based on desktop assessments, which “are prone to uncertainty”. The failure to highlight these areas, which include endangered Fuzzy Box Woodland and Carbeen Open Forest, “may hamper … effective management measures” should problems arrives in the future, the report said.

Georgina Woods, a spokeswoman for Lock The Gate, said the “extensive criticism highlights just how poorly Santos have thought through the consequences and risks”.

“Contrary to Santos’ glib assurances, the committee found that there is risk of more than two metres drawdown of the Pilliga Sandstone, the productive aquifer that recharges the Great Artesian Basin,” she said. “If Santos’ water modelling isn’t capable of figuring that out, it is worse than useless, because it has allowed Santos to misrepresent the risk they’re taking with other people’s water.”

A spokeswoman for Santos, though, said the company “welcomes the review”.

“Santos is currently preparing a response to the submissions as part of the assessment process,”  she said.

A spokeswoman for the Planning Department said Santos had been asked to provide “a detailed response” to the expert advice and other submissions.

“Once the response is received, the Department will finalise its detailed merit assessment of the project in accordance with applicable NSW government policies and guidelines, including the NSW Aquifer Interference Policy,” she said.

The experts’ concerns extend to industrial chemicals used in drilling. They called on Santos to have related hazards and risks “rigorously and transparently assessed”, and ensure that the chemicals are permitted to be imported. 

The panel noted Santos has yet to resolve how it will store and manage salts from produced water, which would amount to 115 tonnes per day in early years. Complicating storage and disposal is the likelihood of metals and radionuclides in the waste. 

Stuart Khan, a water expert at the University of NSW who provided a separate assessment, said the project would generate about 430,500 tonnes of salt over its 25-year life.

“Importantly, the lifespan of this salt storage will need to properly considered,” Professor Khan said. “Salt does not biodegrade in the environment and has an infinite environmental residence time.”

Jeremy Buckingham, Greens mining spokesman, said “the creation of vast amounts of toxic waste and salts has always been the unresolvable problem with coal seam gas”.

“Coal seam gas is unwanted and unnecessary and this [expert] report confirms the fears of farmers and the wider community that it is also unsafe,” Mr Buckingham said.

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