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 km2 — Maximum mine area at one time 2.1 km2 (pits, works areas, recent overburden) — Total mine affected area in Pages River catchment 3.5 km2

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

(90th 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

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

• verburden

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
• verburden dump
• In a 100 year flood overburden dump

would cause less than 0.1m increase in flood level at northern boundary