12 February 2020
20137096-009 Rev A
The depth of weathering and strength of the base roack.
A site investigation with indicative in situ testing locations is provided in APPENDIX B. Optimisation of the in situ testing locations tis o be undertaken during the investigation campaign, along with developing the laboratory testing schedule.
8.0 EMBANKMENT STABILITY
No stability analysis have been carried out for the embankment as yet. However, the design of the embankment has assumed a conservative downstream slope of 2.5:1 (H:V) on the basis of waste rock being used for the downstream shell and the foundation being reasonable quality rock, similar to that visible in the pit walls. The tailings and any soils overlying the rock will have to be removed prior to the construction of the various stages of the embankment. This could be done progressively as the embankment is raised. 9.0 PROVISONAL BILL OF QUANTITIES Preliminary material quantities for the construction of the TSF Starter Dam and subsequent raises, based on the concept design, is detailed in Table 7 (APPENDIX C). it should be noted that two options have been included for the upstream seepage and piping prevention liner for the embankment, as shown in Item 6.
Table 5: Summary of Bill of Quantities.
Item
Description
Units
Quantities
1
Site clearance
-
TBC
m 3
2
Removal of tailings from the Sandstone gully
371,400
m 3
3
Removal of Lime stockpile
TBC
m 3
4
Catchment diversions drain (114 Ha) to RL 335 m
TBC
Stage 1 to 6 removal of 300 mm (indicative) topsoil to be stockpiled
m 3
5
48,100
m 3
Option 1 – Clay upstream liner (Zone 1) Alternative Option 2 - Geomembrane upstream liner (HDPE)
220,000
6
m 3
68,700
m 3
7
Stage 1 to 6, Embankment fill (Zone 3)
5,001,000
m 3
8
Stage 1 to 6, Chimney filter (zone 2B)
56,000
m 3
9
Stage 1 to 6, Blanket filter (zone 2B)
71,000
m 2
10
Stage 1 to 6 Geotextile to encase filter drains
284,000
Increases in the volume due to bulking and contingency are not considered in the quality estimates.
10.0 PRELIMNARY COSTING A cost estimate has been developed which is classified as a Class 4 type costing, ranging between ‘Low’ (15% to -60%) and ‘High (+30% to +120%), as defined by the Golder cost estimating guidelines. The level of
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