Grunching Through Potential Outburst Zones Jack Borg – Tahmoor Underground Colliery

Virgin Content

Drainage Pattern Design

Drilling Results Holes drilled mid-seam. Water return lost, Zone of Soft Coal intersected lots of interconnection between holes.

Drainage Area assigned to each hole = approx. 6500m 2 Amount of gas from each hole (to drain to residual, 4m 3 /t)= 182,000m 3 Time on drainage at time of mining= >200 days HoleCumulative flow CO2 + CH4 (m3) D ,000 D ,000 D ,000 D ,000 D ,000 D106 75,000 D ,000 D ,000

What was found during mining?

Grunching Area

Core Results

Grunching Cycle Mark Up Face Drill FaceStone DustLoad FaceFire Re- Establish Ventilation Muck out & Support with Miner Bolt up Face Estimated cycle time of approx. 150min (360min available/shift) Estimated achievable advance rates of 6m/shift (2 Shots)

Shotfiring Pattern (14 hole grunching pattern) Detonator Requirements 4 x No.1 4 x No. 2 2 x No.3 4 x No.4 Senatel Permitted 1000 (Powergel P1) Use permitted due to CO2 content (>85%) No.1-No.3 delays = primer + 2 plugs No.4 delays = primer + 3 plugs 46 plugs Carrick II 3.6m Electric Detonators

Grunching Success Effective method of advancing areas above TLV at rates of approx. 10m/day Minimal issues with maintaining roadway profile No misfires or issues encountered with using P1 classified explosives Issues Initial estimates of 2 shots/shift were not able to be achieved regularly. Underestimated time required to muck out and support using miner. Limited availability of shotfirers restricted the number of production shifts. Large number of compliance holes in firing face made placement of shotfiring holes difficult. Based on the achieved advance rates not economically sustainable for large areas 12

Summary & Key Learnings Effectively mined approx.100m in an area above the defined threshold values using remote mining methods. Maintain advance rates comparable to those under ‘limited advance rate’ thresholds (12m/day) used at Tahmoor Colliery. Able to mine safely and without the occurrence of any outbursts while mining in coal that contained up to 14m3/t.