Wambo - DA 305-7-2003 MOD 17 Briefing 6 December 2017

Albert Scheepers – General Manager Micheal Alexander – Dir. Projects & Portfolio Management NSW Steven Peart – Manager Environment & Community

1. Overview of MOD 17.

2. Subsidence effects and impacts.

3. Groundwater and surface water conclusions.

4. Proposed conditions.

5. Justification of Modification.

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Agenda

• Continued use of South Bates Underground coal handling

infrastructure located within the Bates South pit.

• Two additional ventilation shafts within existing approved

disturbance area.

• Gas drainage boreholes would be restricted to grassland.

• Delay in the commencement of South Wambo Underground

to allow for access to this coal.

• Extends the life of the operations by 7 years.

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Overview of MOD 17

Modification Components

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Overview of MOD 17

• 18 Mt of ROM coal from

the Whybrow Seam.

• Whybrow Seam

extensively mined at

Wambo.

• Wholly Wambo-owned

land.

• Adjacent to existing open

cut and underground

mining areas.

• No changes to the open

cut operations.

• No change to maximum

production rates or coal

handling operations.

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Subsidence Effects and Impacts

Extent of Conventional

Subsidence

Wollemi Escarpment

• Extensive working knowledge of the Whybrow Seam and

high degree of confidence in prediction modelling.

• Subsidence impacts would continue to be managed in

accordance with:

• Subsidence impact performance measures in the

consent.

• Extraction Plan process – detailed management and

monitoring.

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Subsidence Effects and Impacts

Management of Subsidence Impacts

• No additional impacts on surrounding water supply.

• Incremental impacts are generally confined to the extent of the

Modification longwalls.

• Numerical model developed by Dr Noel Merrick.

• Calibrated against 11 years of continuous monitoring data

(2003 – 2014).

• Peer reviewed by Dr Frans Kalf.

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Groundwater and Surface Water Conclusions

Groundwater Assessment Conclusions

• North Wambo Creek has been diverted around the approved

Wambo open cut operations.

• North Wambo Creek is ephemeral.

• The catchment area of North Wambo Creek is approximately

2% of the catchment area of Wollombi Brook at Warkworth.

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Groundwater and Surface Water Conclusions

North Wambo Creek

Water Supply

• No water used for domestic or stock along the complete length of North Wambo Creek.

• Classified as “less productive” by CLWD (formerly DPI Water).

• No privately-owned land along North Wambo Creek.

Ecological Values

• No permanent pools in the section of North Wambo Creek that would be undermined by Longwalls 23 to 25.

• 1 km of the length above LW 23 and 24 has been historically cleared for agriculture.

• Remaining vegetation is fragmented and affected by previous grazing activities.

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Groundwater and Surface Water Conclusions

Values of North Wambo Creek

• Anticipated to be similar to impacts elsewhere on North Wambo

Creek and the Diversion where subsidence has already occurred at

similar mine geometries:

• Creation of semi-permanent or permanent pools.

• Surface soil cracking and changes in grade that may require local

scour protection works or remediation.

• Direct hydraulic connection has not been observed:

• Extraction of South Bates Underground LWs 11 to 13 (2016 – 2017)

beneath North Wambo Creek Diversion.

• Extraction of North Wambo Underground LWs 1 to 8a (2008 – 2015)

beneath North Wambo Creek (downstream of the Modification

area).

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Groundwater and Surface Water Conclusions

Potential Impacts on North Wambo Creek

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Groundwater and Surface Water Conclusions

• Hunter Lowland Redgum Forest.

• Not considered by Dr Colin Bower to be groundwater dependent.

• Recent drilling in the area showed the depth to groundwater is 4.8 to 13.8 m.

• Groundwater table is generally in consolidated bedrock below colluvium (generally not suitable for rooting).

• Significant monitoring programs have been undertaken at Wambo in areas of undermined vegetation. No observable effects to vegetation health due to reduced access to groundwater have been recorded at Wambo.

• Conditions require Wambo to meet subsidence impact performance

measure:

• Limited to - minor cracking and ponding of the land surface or other impact.

• Negligible environmental consequences.

• Failure to meet these measures is a non-compliance and also

requires an offset of the impact.

• The Extraction Plan provides further detail and confidence about

meeting these measures and how performance will be assessed.

• Wambo will conduct further studies into the potential groundwater

dependence of the riparian vegetation along North Wambo Creek.

• 4 years of mining prior to Longwall 25.

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Proposed Conditions

Riparian Vegetation

• Underground mining and subsidence within WCPL owned land.

• Enables continued use of Wambo infrastructure and workforce.

• Economic recovery of coal resource that would otherwise not be

recovered.

• Facilitate continuity of underground operations (230 personnel).

• Additional royalties in the order of $66 M (NPV).

• Economic and social benefits in the Wambo region associated with

ongoing employment opportunities and expenditure.

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Justification for Modification

Highlights