Santos has released its Environmental Impact Statement (EIS) for its Narrabri Gas Project – and it’s a whopping 7000 pages.
if you’re not committed to reading the Homer’s Iliad of reports (because it’s so damn long), The Leader has done it’s best to summarise it into a cheat sheet.
Fair warning, we are not fluent in scientist, but we’ve done our best to translate it into English (you’ll see what we mean).
Here is the simplified findings of Chapter 11 – Groundwater and geology.
Depressurisation in the target coal seams at depth with the Gunnedah Basin would occur rapidly but vertical transmission of depressurisation into shallow overlying water sources in the Surat Basin and Namoi Alluvium would be attenuated in magnitude and delayed in time by thick aquitard sequences located above the target coal seams
What that means: Depressurisation will happen quickly, but it won't travel to the surface quickly because thick rock layers will slow its progress and lessen the impact.
Maximum predicted change if groundwater pressure in high-value groundwater sources due to the project is less than 0.5 metres, including less than 0.5 metres drawdown of groundwater pressure in the immediately overlying Pilliga Sandstone aquifer of the Surat Basin, and less than 0.5 metres decline of the water table elevation in the Namoi Alluvium aquifer near the northern fringe of the project area.
What that means: The underground watertables near the project are expected to drop by less than half a metres.
Potential impacts on groundwater in the Pilliga Sandstone and Namoi Alluvium from the project are expected to indiscernible in relation to the existing variations in the groundwater pressures and storage volumes that occur in response to existing uses and replenishment, with the expectation that these changes would not be perceptible to existing bore owners.
What that means: Farmers and other bore users won't be able to notice the drop in the underground watertable, as the drop fall within its natural rising and falling cycle.
No significant impacts on existing groundwater users or groundwater dependent ecosystems with the assessment area are predicted, including Hardy's Spring and Eather Spring, which are listed as high-priority springs under the Aquifer Interference Police and by the NSW Government's State of the Catchments 2010 Namoi Region Groundwater.
What that means: Local groundwater users and ecosystems that depend on the groundwater will not be effected.
Potential for impacts on shallow groundwater sources by poorer quality water in the deeper coal seams is assessed to be negligible because the direction of groundwater flow induced by the project would be downward towards the depressurised coal seams.
What that means: The salty water found deeper in the earth shouldn't contaminate the fresh groundwater found closer to the surface, because it will be sucked down and away from the fresh water.
Potential impacts of water-related assets and infrastructure from subsidence caused by depressurisation and compaction of the target seams are assessed to be negligible.
What that means: It is extreme unlikely that any subsidence, or the inwards collapse of earth, will cause damage to assets and infrastructure - like private bores or irrigation equipment.
No significant risk to groundwater from drill holes and installation of coal seam gas wells and groundwater monitoring bores have been identified
What that means: No problem large enough has been found to prevent the drilling and installation of wells.
Fault zones would be unlikely to act as conduits for preferential groundwater or gas flows between deep and shallow groundwater sources due to lack of faulting that extends from the Surat Basin into the underlying Gunnedah Basin
What that means: Salty water and gas are unlikely to contaminate groundwater sources. While both can travel through faults, or fractures, in the earth, the report says there is a lack of faults between the basin where the gas is extracted from and the basin where water is extracted from by farmers.
Proposed beneficial reuse of treated produced water for crop irrigation on a suitable soil type is likely to have similar impacts as the existing irrigated farms within the assessment area, with the potential benefit of additional local recharge to ground water in the irrigated area.
What that means: The salty water extracted from the ground will be treated and reused on crops, and should be as effective as other farms in the region. The treated water will also trickle down into the basin, recharging the groundwater.
Managed releases of treated produced water to Bohena Creek when flow in the creek is greater than, or equal to, 100 megalitres per day is not expect to adversely impact the River Flow Objectives and Water Quality Objectives of the Namoi Catchment area.
What that means: Releasing treated water (salty water than has been extracted and brought up to usable standards), into the creek that runs through the Pilliga forest will be fine as long as it is flowing at a rate of at least 100 megalitres a day.