In September last year, Australia’s premier geotechnical organisation, Geosciences Australia (GA), released a review of potential groundwater impacts from coal seam gas (CSG) mining in Queensland’s Surat and Bowen Basins. GA examined environmental impacts statements (EIS) provided by three companies: Australia Pacific, Queensland Gas Co/British Gas, and Santos Ltd. These are three of the biggest companies pursuing CSG extraction in Queensland.
GA concluded that individual gas wells were unlikely to cause groundwater problems locally. However, they did reach a significant cautionary finding, as follows:
“… .the overriding issue in CSG development is the uncertainty surrounding the potential cumulative, regional scale impacts of multiple developments. The information provided in the assessed EIS documents is not fully adequate for understanding the likely impacts of widespread CSG development across the Surat and Bowen Basins; nor will any level of information or modelling that can be provided by individual proponents.”
Which seems to say that we can’t trust any models, and that we won’t know what will happen till it’s happened! Taken at face value, not an entirely satisfactory situation, to put it midly.
GA went on to recommend a process for ‘staged adaptive management of CSG development’ along the following lines:
- Apply the precautionary principle. Assume excessive groundwater extraction will have impacts. They recommended that there should be explicit requirements to minimize and mitigate any groundwater impacts during gas production
- A regional-scale multistate and multilayer model of cumulative effects of multiple developments, and a regional-scale monitoring and mitigation approach (should) be developed to assess and manage these impacts.’ (whether or not building and calibrating such a model is technically feasible is not clear to me)
- Whatever modeling is undertaken, there is very high level of predictive uncertainty involved, so proponents should consider actions to minimize potential impacts on water balances, eg. by re-injecting ‘treated associated water back into appropriate permeable formation(s) to reestablish pre-development pressure levels’ (one hopes they would be required to more than ‘consider’ these actions).
As I mentioned at the outset, GA is Australia’s preeminent geotechnical (underground science and engineering) organisation. It would be a foolish government that ignored their advice.
In response to widespread public concerns regarding CSG extraction, the Queensland Government has released a policy statement: ‘Protecting your groundwater and the environment’. It promises that the government will:
- regulate CSG operators to ‘ensure that agricultural land remains productive for primary industries’, by
- require environmental management plans to show ‘effective protection of environmental values, including groundwater quality’,
- require ‘periodic underground water impact reports’,
- set ‘groundwater trigger thresholds for impacts on private bores affected by CSG extraction activities’.
It goes on to say:
- triggers will be (a) lowering of the water level by 5 m in aquifers in sandstone (or other ‘consolidated’ material), or (b) lowering by 2 m in shallow groundwaters, or (c) 0.2 m in springs.
- bore owners who think their bore is affected by CSG work can have the CSG operator look into the matter, based on bore records and water use records, and if the CSG work is shown to be the cause, then the CSG company must ‘make good’ under the new regulations, or the owner can appeal to the Land Court.
‘Make good’ means:
- Possibly deepening the bore, or letting the owner use a pump, or ‘establishing an alternative source of supply’.
- If several companies are involved, the government will oversee groundwater impacts in the area (a ‘cumulative management area’), i.e. will monitor, model and prepare cumulative impact reports on, the groundwater, and facilitate the group ‘making-good’.
In an earlier study (Feb 2009), CSG mining company Santos reported, based on their own modelling, that:
- Maximum draw-downs of groundwater in the Bowen Basin coal seam aquifers were likely to be around 600 m and up to 1000 m
- Landholder bores in that area might lose head, even well beyond the CSG fields, but town supply should not be affected.
- Springs and perennial base-flow to the Dawson River are not expected to be affected by the draw-downs.
- In the Roma area (Surat Basin) draw-downs are expected to affect a smaller zone and be smaller, and not affect landowner bores nearby, nor town water supplies.
- Both fields will experience inter-aquifer transfers, (presumably) into the coal seam aquifers.
- No ground subsidence is expected in either basin.
Santos stated then that it will:
- Monitor groundwater during and after CSG extraction, to assess the degree and extent of impacts on groundwater.
- If unwanted effects happen, Santos will fulfil its make good obligations, and/or inject extracted water into affected aquifers, and/or rehabilitate artesian bores nearby to stop head losses (I assume they mean groundwater heads, not Santos executive heads !!!).
I have to say that, while being no expert on groundwater hydrology, I don’t find the combination of the GA review and these statements from Santos, particularly reassuring.