Monitoring the Death of “Protected Swamps”
East Wolgan Swamp is so important it was nationally listed as an Endangered Ecological Community and also state listed under the NSW Threatened Species Conservation Act in 2005, but undermining has ruined it.
The Angus Place Colliery’s Newnes Plateau Shrub Swamp Management Plan 2006 (Swamp Plan) fails to acknowledge these "protected" swamps are vulnerable to damage from longwall mining or to consider protection of this nationally endangered habitat from mine subsidence damage. The Swamp Plan only proposes to monitor damage and, as a last resort, may require ineffective remediation.
As for the monitoring, the Swamp Plan seems to be directed at ensuring surface damage continues without any reduction in mining intensity or adoption of adequate protection zones for streams and swamps.
East Wolgan Swamp is above coal pillars and subsidence would be expected to be much less than above the longwall panels (see opposite). Yet the surface damage is extreme and the Blue Mountains Water Skink (Eulamprus leuraensis) has almost certainly disappeared from the swamp.
After mining and the subsequent cessation of artificial mine effluent discharges through the swamp, the groundwater disappeared from the swamp’s soil profile and had not returned by May 2010 when the peat had dried out, collapsed and cracked.
East Wolgan Swamp is now extremely susceptible to fire damage and exotic species invasion.
The groundwater has drained through the cracked rock below the peat. It is not possible to rehabilitate this site using the Swamp Plan’s remediation strategies (diversions, bunding etc). These techniques will not deal with the primary cause of damage - the cracking of the underlying aquitards!
Centennial's Subsidence Management Status Report for March 2009 incorrectly stated that the crack is ‘minor and the evidence being gathered in the form of sequential photographs is demonstrating that the cracks are rapidly weathering and filling with silt’. The subsequent allegation that stream flow will resume is not supported by any evidence.
Swamp Plan is fundamentally flawed
G.E. Holt and Associates carried out an assessment on the Subsidence Predictions and Subsidence Impact Assessment for the Angus Place Longwall Panels 930 to 980. This report stated that: “There has been minimal surface cracking associated with the subsidence from the mining of the 920 Longwall panel. The same results are expected for subsequent panels 930-980. Consequently, the likelihood of significant negative impacts from mining on the Newnes Plateau Shrub Swamps is very low” (my emphasis).
“The geological sequence that overlies the Angus Place mine workings is one that accommodates mining related movements better than most. The predominantly sandstone sequence is not extremely brittle compared with the sandstones of the Southern Coalfield and appears to allow reduction in subsidence more than what would be expected from a cursory study of the mining parameters. Coupled with this is the fact that mining is moving underneath a relatively flat plateau, intersected by few streams and those stream form the uppermost tributaries where subsidence impact on the stream beds is benign compared with the incised valleys of the Southern Coalfield” (my emphasis).
Clearly the damage to East Wolgan Swamp is not a ‘benign impact’ and it is not an isolated event, as other swamps nearby have been seriously damaged. Why didn’t the regulatory agencies question the above assertions given the hundred or so cliff falls and even more plentiful surface cracks around the Plateau caused by Angus Place Colliery?
The Southern Coalfield Inquiry and the Metropolitan Inquiry both recognised valley-infill swamps as especially vulnerable to subsidence impacts, and these conclusions are equally relevant to Newnes Plateau. Contrary to the assertions by Mr Holt in the Swamp Plan, the Newnes Plateau would appear to have topography similar with the Southern Coalfield. The stream pattern depicted maps of the Swamp Plan doesn’t sit comfortably with the plan’s assertion that the area as ‘a relatively flat plateau intersected by few streams’.
The Swamp Plan being based on wrong geological and geomorphological assumptions and a flawed monitoring strategy that could not detect damage in a timely fashion. The Swamp Plan’s perverse conclusion that longwall mining of Newnes Plateau would be benign demonstrates that the coal industry can’t be trusted to protect significant environmental values, such as the nationally endangered swamps found in the Gardens of Stone. Effective mine subsidence protection zones are needed for these "protected" swamps.