Streams What was What were What are the History/Description Monitoring Remediation Current situation impacted? the impacts? potential causes or contributing factors? Cracking of Presumed The Darkes Forest Mine was created in No monitoring details No known Cracks still visible Waratah bedrock subsidence 1971; very few details available found remediation and surface water Rivulet, from Darkes can be seen to Loss of Woronora Forest disappear down surface water Catchment Colliery cracks. flows (upstream of (appears to Given the Flat Rock return passage of time Swamp) approximately this is indicative of 500 m an area that has downstream) not naturally remediated. Waratah Cracking and Subsidence Longwall mining commenced in 1995. Monitoring by mining Remediation Creek still ceases Rivulet, tilting of related to Longwall widths began 125 m wide and company including attempted using to flow during low Woronora bedrock. longwall mine were increased up to 162 m wide for subsidence, hydrology, drill holes and flow conditions. Catchment extraction Longwall 11. riparian vegetation, sand curtains. Loss of directly macroinvertebrate and These have surface flows Initial cracks were noticed when Longwall beneath fish surveys since been and loss of 10 was undermined. This was followed by Waratah damaged by water from cracking, failure of rockbar WRS3 and Monitoring Rivulet. further mining permanent loss of surface water flows (4-4.5 Ml/d) instrumentation was Tilting to the and fracturing. pools. associated with the extraction of Longwall installed at rockbar WRS1 east resulting Still assessing 11 (Galvin & Associates 2005). prior to commencement of Reduced in alteration latest attempt at Longwall 9. water quality Rehabilitation was attempted in 2006 using of flow remediation with and growth of drill holes and sand curtains in the Subsidence movements sand and iron oxidising fractured rockbar and some preliminary that occurred as Longwall colloidal silica bacterial improvements in water retention behind the 10 approached caused binding agent. mats. rockbar have been noted. instrument failure (Mills & Huuskes 2004). Loss of Risk assessment for Longwall 12 habitat. suggested further impacts were likely. Monitoring at rockbar
Streams What was impacted? What were the impacts? What are the potential causes or contributing factors? History/Description Monitoring Remediation Current situation Waratah Rivulet, Woronora Catchment (upstream of Flat Rock Swamp) Cracking of bedrock Loss of surface water flows (appears to return approximately 500 m downstream) Presumed subsidence from Darkes Forest Colliery The Darkes Forest Mine was created in 1971; very few details available No monitoring details found No known remediation Cracks still visible and surface water can be seen to disappear down cracks. Given the passage of time this is indicative of an area that has not naturally remediated. Waratah Rivulet, Woronora Catchment Cracking and tilting of bedrock. Loss of surface flows and loss of water from permanent pools. Reduced water quality and growth of iron oxidising bacterial mats. Loss of habitat. Subsidence related to longwall mine extraction directly beneath Waratah Rivulet. Tilting to the east resulting in alteration of flow Longwall mining commenced in 1995. Longwall widths began 125 m wide and were increased up to 162 m wide for Longwall 11. Initial cracks were noticed when Longwall 10 was undermined. This was followed by cracking, failure of rockbar WRS3 and loss of surface water flows (4-4.5 Ml/d) associated with the extraction of Longwall 11 (Galvin & Associates 2005). Rehabilitation was attempted in 2006 using drill holes and sand curtains in the fractured rockbar and some preliminary improvements in water retention behind the rockbar have been noted. Risk assessment for Longwall 12 suggested further impacts were likely. Monitoring by mining company including subsidence, hydrology, riparian vegetation, macroinvertebrate and fish surveys Monitoring instrumentation was installed at rockbar WRS1 prior to commencement of Longwall 9. Subsidence movements that occurred as Longwall 10 approached caused instrument failure (Mills & Huuskes 2004). Monitoring at rockbar Remediation attempted using drill holes and sand curtains. These have since been damaged by further mining and fracturing. Still assessing latest attempt at remediation with sand and colloidal silica binding agent. Creek still ceases to flow during low flow conditions.
peat-swamp-subsidence.docx