26 November, 2014

Hightlighting Issues of Concern re Airly Coal EIS

Capertee Valley Community are not anti-development. We just want to ensure that quality data is collected and analysed by good modelling methods to ensure the environs are looked after while mining takes place; the right conditions are placed in their license; the company is compliant with those conditions; and the Government is actively making sure the company is compliant.



The following is extracted from an Expert Report re Subsidence and Groundwater Impacts in planned Airly Mine Extension under Mt Airly and Genowlan Mt.




CENTENNIAL’S DEFINED PLANNING ZONES
EXPERT WRITERS CONCLUSIONS
Zone 1:  (yellow)
Termed the “Shallow Zone”, where there is low cover and only first workings using bord and pillar methods are proposed.
Predicted maximum subsidence = 26mm.

Acceptable as is.
Zone 2: (dark blue)
Termed “Partial Pillar Extraction Zone”, located between the “Shallow Zone” and a postulated line where cliffs could be affected.
Predicted maximum subsidence = 65mm.

This mining zone constitutes a relatively small proportion of the mine area. Therefore given the uncertainty in respect to the subsidence movements, and the very adverse consequences of cliff line instability, it would appear to be wise and appropriate to eliminate this mining zone. In this case, first workings would be adopted from the low cover area through to the plateau area.

Zone 3: (green)
A zonal footprint beneath cliff lines where only first workings would be employed.
Predicted maximum subsidence = 65mm.

The design is considered appropriate provided it is not possible that the workings in this zone can become flooded in the long term. If flooding can occur the expected subsidence and surface tilts are greater than are acceptable for safe guarding the cliff line and pagoda structures

Zone 4: (pale blue)
The footprint of the old oil shale mine workings where extraction of coal beneath the level of the oil shale workings would interact with those workings.
Predicted maximum subsidence = 200 to 500mm.

It is predicted that new surface subsidence will be in the range 200mm to 500mm with tilts up to 17mm per metre. It is certain that such subsidence movements will cause substantial additional cracking in the surface area above the old workings and will cause cliff line instability in the escarpments around the perimeter of the old workings. In my opinion, this level of surface damage should be unacceptable to Government authorities. It is my opinion that mining beneath the old oil shale mine should be limited to first workings.

Zone 5: (pink)
Beneath the plateau areas involving panel and pillar extraction.
Predicted maximum subsidence = 106mm.

Given that the experience at Clarence Colliery is the basis for the Airly Extension mine design, it is my opinion that the panel and pillar design should target the same surface subsidence as at Clarence, namely 20mm to 30mm.

Zone 6 - however omitted in the defined zones but in the Executive Summary of Appendix E (Groundwater) there is a statement that “there is no mining beneath Gap Creek and Genowlan Creek (and to a distance of 20m from the creeks) where the depth of cover is less than 40m”.

I have drawn attention to the fact that Appendix E of the EIS states there would be no mining beneath Gap Creek and Genowlan Creek where cover is less than 40m. In my opinion, failure to incorporate this zone in the mine planning presented in the EIS is a fundamental issue that warrants resubmission of the EIS.
Future Mining Defined  Zones

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