BI CKHAM COAL PROJECT W ater Resource Assessm ent: Surface W ater I - PowerPoint PPT Presentation

BI CKHAM COAL PROJECT W ater Resource Assessm ent: Surface W ater I ssues Presentation to Pages River W ater Users 3 0 October 2 0 0 6

Surface W ater – Topics: • How much area will be affected? • How much water is required to operate the mine? • How much runoff will be retained? • Water management strategy • Erosion and sediment control • Flooding

How m uch area w ill be affected? • Affected catchment areas: — Pages River at Gundy 1,050 km 2 — Maximum mine area at one time 2.1 km 2 (pits, works areas, recent overburden) — Total mine affected area in Pages River catchment 3.5 km 2

Year 10 indicative mine layout

How m uch w ater is required? Exam ple - Year 1 0 , average rainfall • Dust Suppression: 240 ML • Coal stockpiles and handling: 100 ML • Total: 340 ML

How m uch runoff w ill be retained? Exam ple: Year 1 0 , average rainfall • “Controlled” areas: — Pits = 88 ha — Haul roads and works areas = 33 ha — Active and shaped overburden = 87 ha — Total = 208 ha • Runoff from “controlled” areas = 324 ML • Natural runoff from “controlled” = 94 ML

W ater Managem ent Strategy - 1 • Natural catchm ents — Supplement existing dams — Stock water — Overflow to Pages River or Kingdon Ponds • Rehabilitated overburden dum ps — Similar water quality to natural catchments — Stock water — Supplementary water for mine if required — Overflow to Pages River or Kingdon Ponds

W ater Managem ent Strategy - 2 • Recent overburden dum ps — Rehabilitate as soon as practical — All runoff to sediment dams — Option to discharge after treatment in accordance with requirements • De-w atering bores — Relatively low salinity water — Beneficial use options

W ater Managem ent Strategy - 3 • Pits, haul roads and w ork areas — Minimise areas — All water reports to isolated “dirty” water system — Re-use runoff for dust suppression and coal handling — Mixture of surface and groundwater likely to have suitable EC for irrigation of overburden — Zero discharge from site

Erosion Control • Progressive construction of overburden dumps from outside perimeter • Slope shape based on geomorphic principles • Progressive rehabilitation with grass • Selective tree planting after grass established

Typical slope profile

Sedim ent Control • Sediment dams - EPA requirements (90 th percentile 10 day storm) • 7 sediment dams - total 85 ML capacity • Sediment dam water available for: − Transfer to Mine Water Dam for re-use within mine − Discharge after treatment (less than 50 mg/L suspended solids) • Flocculate suspended solids using gypsum

Flood Assessm ent • Flood estimation – RORB model using Bickham gauge data • HEC-RAS hydraulic model for existing & proposed conditions : — Flood levels — Channel velocity & shear stress — Floodplain velocity & shear stress

Flood Profiles Pages River Bickham Coal 395 Legend WS 100 year 390 WS 5 year Ground 385 Elevation (m) 380 375 370 overburden 365 4114. 4367. 4565. 1120 1400 1760 2050 2290 2540 2720 2980 3310 4720 5000 5220 5440 5810 6110 6540 6940 250 510 750 360 0 1000 2000 3000 4000 5000 6000 7000 Main Channel Distance (m)

Flood Assessm ent Results • All of 5 Y & most of 10 Y floods, contained in the channel adjacent to the floodplain • Potential channel erosion highest for these floods • These floods not affected by the overburden dump • In a 100 year flood overburden dump would cause less than 0.1m increase in flood level at northern boundary