Corner Marvel Loch Southern Cross Road and Project ...€¦ · and Expansion of Open Pit Mining at...

Design Report - Battler Evaporation Pond

Corner Marvel Loch – Southern Cross Road and

Glendower Road, Southern Cross, WA Project:

LGK8492019D

Rev 1

30 September 2019

Client:

Indus Mining Services Pty Ltd

Project: LGK8492019D Design Report - Battler Evaporation Pond Site: Battler Evaporation Pond, Corner Marvel Loch – Southern Cross Road and Glendower Road, Southern Cross WA Client: Indus Mining Services Pty Ltd P a g e 2 of 18

30 September 2019 To Indus Mining Services Pty Ltd 19-21 Casino St, Welshpool WA 6106 Dear Sir, RE: Design Report - Battler Evaporation Pond, Corner Marvel Loch – Southern Cross Road and Glendower Road, Southern Cross WA This letter presents our design report on Battler Evaporation Pond, Southern Cross, WA. If you have any queries related to the report or we can be of further assistance, please do not hesitate to contact local geotechnics or the undersigned. For and on behalf of Local Geotechnics. Dr. Harun Meer Ph.D.(Geotech), M. Eng. (Geotech), B. Eng. (Civil), MIE Aust

Director Local Geotechnics Project LGK8492019D

Design Report - Battler Evaporation Pond

Site Location Corner Marvel Loch – Southern Cross Road and Glendower Road, Southern Cross, WA

Rev Description Date Prepared by Approved by

0 Issued to client 25 Sep 2019 R Khan H Meer

1 Issued to client 30 Sep 2019 R Khan H Meer


TABLE OF CONTENTS

1.0 INTRODUCTION ........................................................................................................... 6 2.0 PREVIOUS STUDIES ................................................................................................... 6 3.0 SITE SETTING .............................................................................................................. 7

3.1 Surface Conditions ................................................................................................... 7 3.2 Regional Geology ..................................................................................................... 7 3.3 Site Geology ............................................................................................................. 7 3.4 Groundwater Information .......................................................................................... 7

4.0 DESIGN CRITERIA ....................................................................................................... 8 5.0 DESIGN CONSIDERATIONS ....................................................................................... 8 6.0 EMBANKMENT DESIGN .............................................................................................. 9 7.0 EMBANKMENT STABILITY ASSESSMENT ............................................................... 9

7.1 STABLPRO Slope Model.......................................................................................... 9 7.2 Results and Discussions ......................................................................................... 10

8.0 EMBANKMENT FILL MATERIALS ............................................................................ 11 8.1 Soil Type 1 for Zone1 – Sandy/Silty/Gravelly CLAY (CL/CH). ............................... 11 8.2 Soil Type 2 for Zone2 – Sandy/Silty/Gravelly SOIL (SM/SP/SC/GM/GP/GC/ML) . 11

9.0 EARTHWORKS AND EMBANKMENT CONSTRUCTION ........................................ 12 9.1 Site Clearance ........................................................................................................ 12 9.2 Excavation for Ponds and Embankment Base ....................................................... 13 9.3 Embankment Construction ..................................................................................... 13 9.4 Placing of Earthfill and Equipment .......................................................................... 14 9.5 Moisture Control and Compaction .......................................................................... 15 9.6 Quality Assurance (QA) Testing ............................................................................. 16

10.0 SURVEY MONITORING SCHEME AND RECOMMENDATIONS ............................. 17 11.0 LIMITATION OF USE .................................................................................................. 18 12.0 REFERENCES ............................................................................................................ 18

LIST OF FIGURES

Figure 1. Site Location Map (source: Google Maps) Figure 2. Grading Limits for Battler Embankment Fill Materials LIST OF TABLES

Table 1. Soil Properties Adopted in Models Table 2. Slope Stability Analysis Results APPENDICES

Appendix A: Drawings of Evaporation Ponds Appendix B: Embankment Stability Assessment Models


EXECUTIVE SUMMARY

Local Geotechnics (LG) was engaged by Indus Mining Services Pty Ltd (Indus Mining, the client) to undertake design of the proposed evaporation pond embankments at corner of Marvel Loch – Southern Cross Road and Glendower Road, Southern Cross, WA (site).

The 1: 250,000 Geology Series map of the Southern Cross sheet, issued by the Geological Survey of Western Australia, indicates that the site is mostly underlain by clayey silty sand; buff or red, with quartz fragments and calcareous nodules; mainly colluvial deposits. The regional water table setting is interpreted to broadly conform to topography. Within the Project Area, exploration holes indicate a water table setting of between 342 to 348 m RL which is approximately 45 mbgl.

As part of the dewatering strategy for mining at the Battler Pit, the proposed evaporation pond will be built. DEWR approved to construct such a pond with a number of conditions. Main conditions are: (1) Pond base to be ripped, (2) Embankment (or wall) to be compacted, (3) Capacity of 52,600 kL, and (4) An interceptor drainage system around the perimeter of the pond.

Indus Mining studied 9 options by varying ponds cut and fill volume for maximising storage capacity. The aim of the study was to maximise surface area for evaporation while reducing the amount of cut and fill required to build the dams.

LG designed the most preferred pond embankment option, out of the 9 option studies, that comprised three terraced ponds, Pond 1 to Pond 3. The design fulfilled the DEWR conditions. Appendix A included the designed general arrangement plan, cross sections A-A, B-B, C-C and long section, D-D, of the evaporation pond embankments. They will be constructed adjacent north of the existing mine pit on 3 different ground elevations as follows:

• Pond 1 - Floor elevation varies between 381 and 383 m RL

• Pond 2 - Floor elevation varies between 377 and 380 m RL and

• Pond 3 - Floor elevation varies between 373 and 374 m RL.

The following are the facts and figures of the evaporation ponds:

• Ponds’ boundary embankment height: varies between 2 m and 5 m

• Intermediate embankment between Pond 2 and Pond 3: 8 m high from Pond 3’s floor and 5 m high from Pond 2’s floor

• Intermediate embankment between Pond 1 and Pond 2: 5 m high from Pond 2’s floor and 4m high from Pond 1’s floor

• Design water depth in each dam/pond:

o Pond 1 - water depth varies between 1 m and 3 m.

o Pond 2 - water depth varies between 1 m and 4 m and


• Free board (distance between dam crest and water level) = 1 m

• Width of embankment crest = 6 m

• Embankment slope: Upstream 1V:3H and Downstream 1V: 2.5H

• Total water volume capacity = approximately 102 ML

• The embankments are water retaining structures with a minimum of 1m ‘key’ embedded into insitu ground.

• A 1.0 m deep cut off drain along the external toe of the embankment. This cut off drain will be running to a collection sump.


Embankment Sections A-A, B-B and C-C were modelled using a Slope Stability Analysis Program, STABLPRO Version 2015.4.4 of Ensoft Inc. Critical failure surface and corresponding Factor of Safety (FoS) were determined using Bishop’s method. FoS equal to or greater than 1.5 for steady state condition indicates a stable slope. All the embankment sections, modelled, have FoS greater than 1.5, which indicates having stable slopes.

Embankment fill materials, earthworks, embankment construction, QA testing specifications survey monitoring scheme and recommendations are presented in Sections 8, 9 and 10.

It is highly recommended that a geotechnical engineer should supervise (Level 2 supervision) the site activities to ensure that all layout area have been adequately cleared, materials are assessed for zoned embankment, QA testing are undertaken and that the dam embankment is constructed and compacted as per the design specification.


1.0 INTRODUCTION

Local Geotechnics (LG) was engaged by Indus Mining Services Pty Ltd (Indus Mining, the client) to undertake design of the proposed evaporation pond embankments (dam) at corner of Marvel Loch – Southern Cross Road and Glendower Road, Southern Cross, WA (site).

The pond site is located around 340 km east of Perth, WA and 14 km southeast of the Southern Cross township. The site location map is shown in Figure 1.

Figure 1. Site Location Map (source: Google Maps)

For mining dewatering management purpose, construction of a minimum of 52.6 ML capacity evaporation pond is required by the governing authority, Department of Water and Environmental Regulation (DWER), Government of Western Australia. This report presents the main elements of the evaporation pond embankment design. 2.0 PREVIOUS STUDIES

The following reports and studies were reviewed and considered in design of the proposed evaporation pond embankments:

• Local Geotechnics Report (2019) - Geotechnical Investigation Report, Battler Evaporation Pond, Corner Marvel Loch– Southern Cross Road and Glendower Road, Southern Cross WA, No. LGK8492019GI_Rev0, dated 22 September 2019.

• Mining Plus Memorandum (2019) – Indus Battler Evaporation Pond – Design Option Study, rev 1, Dated 10 July 2019.

Approximate Site Location


• IMD Mining Proposal (2017) - Battler Gold Project, IMD Gold Mines Pty Ltd, Reopening and Expansion of Open Pit Mining at the Battler Gold Mine, Southern Cross, Tenements Under Application: M77/1285, dated 29 September 2017.

• Works Approval (2019) – Department of Water and Environmental Regulation (DWER), Government of Western Australia, Works Approval Number W5995/2016/1, dated 22 July 2019.

3.0 SITE SETTING

3.1 Surface Conditions

The topography of the development site was observed to be gently sloping down from south to north, approximately from 385mRL to 374mRL. The surface was accessible by 4WD vehicle and drilling rig. The site was observed to be covered with medium to large size trees and bush.

3.2 Regional Geology

The Project Area is located in the Coolgardie Interim Biogeographic Regionalisation of Australia (IBRA) region, specifically within the Southern Cross Subregion (COO2) of the Coolgardie Region (CALM 2003). This subregion has subdued relief, comprising gently undulating uplands, which are dissected by broad valleys with bands of low greenstone hills (Source: IMD Mining Proposal (2017)).

The site is located in the 'Southern Cross Terrains' of the Yilgarn Craton. The Yilgarn Craton is composed of granite strata which are interrupted by parallel Archaean Greenstone intrusions.

The Battler tenements lie within the Southern Cross Greenstone Belt hosted within an Archaean mafic and ultramafic succession. The region has inclusions of Banded Iron Formations (BIF) and minor carbonaceous shaley sediments now metamorphosed to lower grade amphibolite facies. The Belt extends discontinuously for approximately 400 km, from north of Southern Cross to Ravensthorpe near the southern coast of Western Australia, with a regional strike trend of north-northwest.

3.3 Site Geology

The 1: 250,000 Geology Series map of the Southern Cross sheet, issued by the Geological Survey of Western Australia, indicates that the site is mostly underlain by clayey silty sand; buff or red, with quartz fragments and calcareous nodules; mainly colluvial deposits. A small portion in the south of the site is underlain by Chlorite-tremolite rock; with fine-grained acicular textures; lacks plagioclase; derived from komatiitic basalt.

3.4 Groundwater Information

No groundwater information was available from the geotechnical site investigation, Local Geotechnics Report (2019).

The following groundwater information was extracted from the IMD Mining Proposal (2017):


The regional water table setting is interpreted to broadly conform to topography. Within the Project Area, exploration holes indicate a water table setting of between 342 to 348 mRL which is approximately 45 mbgl. The measured water table setting may be influenced by residual and cumulative drawdown affects from both historical and current abstraction practices. Regional groundwater flow directions are expected to be towards Lake Koorkoordine to the north and northwest. However, local groundwater flow tends to be west and northeast from the Project Area.

4.0 DESIGN CRITERIA

Indus Mining Services is planning to start mining the Battler Pit. As part of the dewatering strategy the proposed evaporation pond will be built. DEWR approved to construct such a pond with the following conditions.

• Pond base to be ripped

• Embankment (or wall) to be compacted

• Capacity of 52,600 kL

• Construct a sub-surface interceptor drainage system around the perimeter of the pond to intercept lateral seepage.

• Install sump pumping on the pond perimeter in locations of preferred pathways

• Freeboard markers on stage 1 and stage 2 installed that allow visual measurement of the freeboard height.

5.0 DESIGN CONSIDERATIONS

The following points were considered in designing the pond embankment:

• Embankment base and keyway will be cut into the insitu ground.

• Balanced cut and fill material volume all across the pond layout area.

• Utilising material being cut form the pond area and mined from the open pit for the construction of the embankment.

• The embankments (walls) are water retaining structures with a minimum of 1m ‘key way’ to ensure that any lateral natural seepage that occurs is more than 1 metre below natural surface to meet the current approval criteria.

• Inclusion of a 1.0m deep cut off drain along the external toe of the embankment. This cut off drain will be running to a collection sump.

Indus Mining studied 9 options by varying ponds cut and fill volume for maximising storage capacity. The aim of the study was to maximise surface area for evaporation while reducing the amount of cut and fill required to build the dams.

LG undertook the design of the most preferred pond embankment option out of the 9 option studies. The preferred embankment option will be presented in the following sections.


6.0 EMBANKMENT DESIGN

LG designed the most preferred pond embankment option, out of the 9 option studies, that comprised three terraced ponds, Pond 1 to Pond 3. The design fulfilled the DEWR conditions. They will be constructed adjacent north of the existing mine pit on 3 different ground elevations as follows:

• Pond 1 - Floor elevation varies between 381 and 383 m RL

• Pond 2 - Floor elevation varies between 377 and 380 m RL and

• Pond 3 - Floor elevation varies between 373 and 374 m RL.

Appendix A included the designed general arrangement plan, cross sections A-A, B-B, C-C and long section, D-D, of the evaporation pond embankments.

The following are the facts and figures of the evaporation ponds:

• Ponds’ boundary embankment height: varies between 2 m and 5 m

• Intermediate embankment between Pond 2 and Pond 3: 8 m high from Pond 3’s floor and 5 m high from Pond 2’s floor

• Intermediate embankment between Pond 1 and Pond 2: 5 m high from Pond 2’s floor and 4m high from Pond 1’s floor

• Approximate pond layout area (including 3 ponds): 310 m wide x 350 m long

• Design water depth in each dam/pond:


o Pond 2 - water depth varies between 1 m and 4 m and


• Free board (distance between dam crest and water level) = 1 m

• Width of embankment crest = 6 m

• Embankment slope: Upstream 1V:3H and Downstream 1V: 2.5H

• Total water volume capacity = approximately 102 ML

• The embankments are water retaining structures with a minimum of 1m ‘key’ embedded into insitu ground.

• A 1.0 m deep cut off drain along the external toe of the embankment. This cut off drain will be running to a collection sump.

7.0 EMBANKMENT STABILITY ASSESSMENT

7.1 STABLPRO Slope Model

Embankment Sections A-A, B-B and C-C were modelled using a Slope Stability Analysis Program, STABLPRO Version 2015.4.4 of Ensoft Inc. Critical failure surface and corresponding Factor of Safety (FoS) were determined using Bishop’s method. STABLPRO is a computer program developed by Ensoft Inc. for the general solution of slope-stability problems using a two-dimensional limiting equilibrium method. The original program was developed by Ronald A. Siegel at Purdue University in 1975. Program STABLPRO features unique random techniques, uses most published methods, for generation of potential failure surfaces for subsequent determination of the most critical surfaces and their corresponding factors of safety.


Three soil types were used in the model analysis.

• Soil Type 1 was used for upstream clay core material,

• Soil Type 2 was used for downstream general fill material,

• Soil Type 3 was used for natural insitu ground. Soil properties are shown in Table 1. Table 1. Soil Properties Adopted in Models

For each embankment section, one piezometric surface following the pond’s water level was assigned.

7.2 Results and Discussions

STABLPRO program searched for a critical slip surface and corresponding Factor of Safety (=Resisting shear strength/Acting shear strength). STABLPRO model outputs are included in Appendix B. Critical slip surface was indicated by a red line and the Factor of Safety (FoS) obtained was shown in each model (Appendix B). Table 2 shows the summary of the stability assessment results. Table 2. Slope Stability Analysis Results

Embankment Section Factor of Safety (FoS)

Section AA- Steady State Condition 6.15

Section BB- Steady State Condition 1.91

Section CC- Steady State Condition 2.35

Factor of Safety equal to or greater than 1.5 for steady state condition indicates a stable slope. All the embankment sections, as shown in Table 2, have FoS greater than 1.5, which indicates a stable slope.


8.0 EMBANKMENT FILL MATERIALS

Pond embankment was designed as two zoned earthfill embankment, Zone 1 comprising upstream clay core and Zone 2 comprising downstream wing with general backfill. Following two soil types were assigned in two zones as fill material (or earthfill) for the embankment.

8.1 Soil Type 1 for Zone1 – Sandy/Silty/Gravelly CLAY (CL/CH).

Material for Zone 1 of the embankment shall consist of a selected impervious mixture of soil. Rock fragments having a maximum dimension of more than 100 mm will not be permitted in Zone 1. Should stones, cobbles, rock fragments or hard clay lumps that interfere with compaction, they shall be broken down or removed before being transported to the dam embankment.

The properties of Zone 1 material when compacted in the embankment shall be as follows:

(i) The gradation, as determined in accordance with AS 1289.3.6.1, shall be such that:

• not less than 70 per cent, by weight, shall pass a 4.75 mm sieve;

• not less than 30 percent, by weight, of the material passing the 4.75 mm sieve shall pass a 0.075 mm sieve.

(ii) The plasticity index, as determined in accordance with AS 1289.3.3.1, shall be not less than 15 per cent nor shall the liquid limit exceed 80 per cent when determined in accordance with AS 1289.3.1.1.

8.2 Soil Type 2 for Zone2 – Sandy/Silty/Gravelly SOIL (SM/SP/SC/GM/GP/GC/ML)

Material for Zone 2 of the embankment shall consist of a general mixture of soil. Rock fragments having a maximum dimension of more than 200 mm will not be permitted in Zone 2. Should stones, cobbles, rock fragments or hard clay lumps that interfere with compaction be found in Zone 2 material, they shall be broken down or removed before being transported to the dam embankment.

Figure1 shows generalised grading limits for embankment fill materials, Soil type 1 and 2. In situ materials available in the pond layout area are likely to be suitable for embankment fill materials. A geotechnical professional engineer can assist assessing Type 1 and Type 2 materials encountered onsite.


Figure 2. Grading Limits for Battler Embankment Fill Materials

9.0 EARTHWORKS AND EMBANKMENT CONSTRUCTION

Earthworks should be carried out in a controlled manner in general accordance with the Australian Standard AS 3798-2007 “Guidelines on Earthworks for Commercial and Residential Developments”. The following general guidelines should be followed during preparation of the site areas within the proposed development footprints:

9.1 Site Clearance

• The Contractor shall clear the required excavation area, the foundations for the embankments, borrow areas, surfaces of stockpile sites, disposal areas and access track. The clearing shall include the felling, removal, piling and disposal of all trees, shrubs, saplings and other vegetable material together with the removal of all fences within the area to be cleared.

• Strip topsoil and any uncontrolled fill or other deleterious material and stockpile separately. Topsoil is defined as the surface or top layer of soil including fine roots, the herbaceous vegetation and overlying grass and is characterised by the presence of organic matter. Topsoil removal shall not extend more than 2 metres outside the limits of excavation and the surface shall not be disturbed beyond these limits.

0

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0.0001 0.001 0.01 0.1 1 10 100

Perc

en

t P

assin

g

Particle Size (mm)

Grading Curves - Battler Evaporation Pond Materials

Type 1 (CLAY)

Type 1 (CLAY)

Type 2 (Gen.Fill)

Type 2 (Gen.Fill)


9.2 Excavation for Ponds and Embankment Base

• Excavation for the pond and embankment bases shall be the required excavation to the cut lines, grades and dimensions shown on the Drawings or as directed by the Superintendent and shall include the stripping of all soil, vegetable matter of all kind including stumps, roots and all other objectionable materials, together with weak, loose, friable or permeable soils. This also includes the removal of material that might interfere with the bonding of the embankment with the foundations or the compaction of the embankment and the removal of materials of inadequate strength.

• Materials excavated from the area and suitable for incorporation in construction shall wherever possible be placed directly in the areas. Excavated materials suitable for use in construction, which cannot be used immediately shall be stockpiled within stockpile areas approved by the Superintendent.

• A geotechnical engineer appointed (Level 2 Supervision) by the Superintendent shall classify the excavated materials, their suitability to use as ‘Type 1 or Type 2’ fill.

• The pond floor near and under the embankment base shall, when completed, present an appearance of uniform texture and general smoothness without irregularities or as accepted by the supervising engineer.

9.3 Embankment Construction

• The embankment shall be constructed to the lines, grades and dimensions shown in the Drawings and directed by the Superintendent.

• The upstream and downstream faces and crest of the embankment shall, when completed, present an appearance of uniform texture and general smoothness without irregularities.

• The Contractor shall maintain construction of two zones as shown in the Drawings, e.g., upstream Clay fill zone (Zone1: Type1 material) and downstream General Fill zone (Zone 2: Type 2 material) from base to the crest of the embankment. However, during construction supervising engineer can decide the type of materials to be used.

• Material for construction of the embankment shall be obtained from the sources specified, approved and determined the Superintendent. Each load of the materials placed in the dam embankment, whether from required excavation, from stockpiles, from borrow areas or processing plants shall be so placed as to secure, on the embankment, the best practicable distribution of the material. If material in any zone has become contaminated with material from another zone or with topsoil or other objectionable material from the passage of construction machinery or by any other means, the contaminated material shall be entirely removed.

• If the surface of the exposed material in Zones 1 and 2 is too dry or smooth to bond properly with newly placed fill, it shall be moistened and scarified in a manner to provide a satisfactory bonding surface before the new fill is placed upon it. During compaction of new fill, the compaction equipment shall completely overlap the contact surfaces.


9.4 Placing of Earthfill and Equipment

• The Contractor shall perform 2 roller trial embankments, constructed on a generally level area not less than 30 metres wide by 15 metres long. One roller trial is required for the Zone 1 materials and the other to simulate construction of Zone 2. The purpose of these trials is to establish the suitability or otherwise of the proposed compaction equipment, to assess the suitability of the proposed methods of conditioning and stockpiling of the material and to establish the optimum placing and compacting methods that will result in the specified material properties being consistently achieved in the pond embankment. Established methodology, equipment type, moistening method, compaction effort should be recorded and shared with the Superintendent.

• Tamping rollers, of the 'sheepsfoot' type are envisaged as being a satisfactory roller type for compaction of Zone 1 & 2 materials. If zone 2 comprising more sandy or granular type materials, 10 tonne vibrating roller can be used in this zone. A scraper can be used at any of the zones if recommended level of compaction can be achieved.

• Should stones, cobbles, rock fragments or hard clay lumps that interfere with compaction be found in Zones 1 and 2 material, they shall be broken down or removed before or after being transported to the dam embankment.

• Material for use in Zone 1 of embankment shall be conditioned in the borrow pit or source, excavated and then stockpiled prior to placement in the embankment. Such stockpiles shall be operated separately from other operations. Also, materials conditioning can be conducted onsite (dam wall) before starting of compaction.

• Proof roll the excavated/cleared area in whole embankment layout area, either by a heavy sheepfoot or vibrating roller, depending on clayey or sandy ground.

• Zone 1 material of the dam embankment including the key would generally be placed over in situ materials, i.e., foundation material. The preparation of the foundation ground shall be in accordance with the following requirements:

i. Pockets of weak or otherwise unsuitable material shall be removed below the general foundation level as directed by the Superintendent.

ii. The foundation surface, immediately prior to receiving Zone 1 & 2 material, shall have all water removed from the depressions and the top 150 mm of foundation material shall be free from intruded bedrock, sufficiently moistened and compacted to 98% of MDD in accordance with AS1289.5.1.1, to such condition that the first layer of fill will bond with the foundation in the same manner as specified for the bonding of subsequent layers of fill materials.

• The Contractor shall handle and spread earthfill, i.e., Type 1 and Type 2 materials, on the embankment so as to produce a uniform distribution and gradation of the earthfill throughout Zone 1 & 2. Clusters of rock that interfere with compaction shall be removed.

• The Contractor's operations in handling, spreading and compacting material on the embankment shall result in an even distribution and gradation of the materials throughout the zone. The zone shall be free of lenses, streaks, laminations, layers of material differing substantially from the surrounding material in the zone or other discontinuities and the density shall be uniform throughout each compacted layer.


• The surface of the prepared foundation or the surface of any layer of Zones 1 and 2 material shall be worked with harrow, scarifier or other suitable equipment, to a sufficient depth to provide a satisfactory bonding surface and moistened if necessary, before the next succeeding layer of material is placed. The Contractor shall minimise the incidence of plant, particularly rubber tyred plant, travelling on the prepared and scarified surface of the Zone1 material before placement of the overlying layer has been completed. Where this occurs the Contractor shall take such steps as are necessary to ensure that laminations do not exist between successive layers of the fill. Such measures include reducing layer thickness to ensure the compactor feet penetrate the full layer thickness or by tyning through the loose layer before compaction.

• The material shall be placed in continuous horizontal layers from abutment to abutment or the end of the section being constructed for the full width of the zone. The thickness of each compacted layer shall be not more than 300 mm, unless otherwise directed by the Superintendent.

9.5 Moisture Control and Compaction

• Unless otherwise approved or directed by the Superintendent, the material in each layer (i.e., lift) shall have a moisture content, during and after compaction, within the range of:

- Zone 1 (Clay) - optimum moisture content minus (–) 2% to the optimum moisture content.

- Zone 2 (General Fill) - optimum moisture content minus (–) 3% to the optimum moisture content.

• The optimum moisture content of the material shall be the moisture content that is required to achieve the peak converted wet density when tested in accordance with the method given in AS 1289.5.7.1. If the moisture content does not fall within the required limits, the Contractor shall treat the material in such a manner that the moisture content is brought to within the required limits.

• The moisture content shall be uniform throughout the layer. The moisture limits may be varied at the direction of the Superintendent but in general the permitted range of moisture content will be 2%. The Superintendent may accept material placed up to 1% wet of the ranges shown, provided that the material has been compacted to the density specified in the following Clause.

• The adjusted moisture variation shall be calculated in accordance with the method given in AS 1289.5.7.1, using the standard compactive effort in accordance with AS 1289.5.1.1.

• The Contractor shall establish procedures for conditioning the earthfill for Zone 1 and 2 at its source so as to bring it within the range of moisture contents specified above prior to its haulage to the embankment.

• If the surface of the prepared foundation or the surface of any layer of earthfill material is outside the moisture content limits specified above or is too wet for proper compaction and bonding of the layer of material to be placed thereon, it shall be allowed to dry or be worked with harrow, scarifier or other suitable equipment to reduce the moisture content to the required range. The layer shall then be re-compacted and a satisfactory bonding surface shall be provided before the next succeeding layer is placed.


• If the surface layer of earthfill material is left exposed for any length of time, the Contractor shall prevent drying out of the underlying material by periodic watering, by covering, by maintaining the surface layer in a loosened condition or by other methods approved by the Superintendent. Should drying out of underlying material occur, this material shall be treated to bring it within the Specification requirements for moisture content.

• When each layer of material in a zone of fill has been conditioned to have the specified moisture content, it shall be compacted with the approved rollers until the field density determined in accordance with AS 1289.5.3.1 meets the criterion that the Hilf density ratio (RHD) is equal to or greater than 98% when tested in accordance with AS 1289.5.7.1 using standard compactive effort in accordance with AS 1289.5.1.1. If the result of any test of the Hilf Density Ratio of a sample is less than 98%, the Contractor shall scarify the layer, correct the moisture content and recompact the layer to meet the criteria set out in this Clause.

• Material placed in contact with the foundation shall have a moisture content as directed by the Superintendent, but generally will not be more than 4% in excess of that specified in the 1st Clause above. After completion of spreading, the material shall be compacted until the field density determined in accordance with AS 1289.5.3.1 meets the criterion that the Hilf roller efficiency (ER) is in excess of 100 per cent when obtained from the compaction test carried out in accordance with AS 1289.5.7.1 using standard compactive effort in accordance with AS 1289.5.1.1. If the results of a test of the Hilf roller efficiency of a sample is less than 100 per cent, the Contractor shall scarify the layer, correct the moisture content and re-compact the layer to meet the criteria set out in this Clause.

9.6 Quality Assurance (QA) Testing

The Contractor shall carry out testing as indicated in ‘Section 9.5 - Moisture Control and Compaction’ during construction of the embankment and as may be required by the Superintendent.

The Quality Assurance (QA) tests shall include but not be limited to:

i. Measurements and records of layer thickness

ii. Check and record for layer lamination, contamination, uncontrolled compaction scenarios

iii. Insitu density

iv. Particle size distribution

v. Plasticity index

vi. Moisture content

vii. Moisture variation and

viii. Hilf density ratio (RHD).

If the above-mentioned QA tests are found to be inconvenient or difficult by existing or available laboratory resources, other conventional and similar tests can be proposed and approved by the Superintendent.

Testing shall be undertaken by an independent laboratory registered with the National Association of Testing Authorities (NATA).


The frequency of testing for final acceptance of each compacted section and layer of fill in the embankment will be one of the following three criteria:

a) at least one set of tests for each day’s production;

b) at least one set of tests for every two-layer placed in one section of approximately 100 m long (each layer = 300 mm thick);

c) at least one set of tests for every 1,000 cubic metres of material placed.

The results of all testing shall be forwarded to the Superintendent for approval before work on the next layer of the embankment material can commence.

It is highly recommended that a geotechnical engineer should supervise (Level 2 supervision) the site activities to ensure that all layout area have been adequately cleared, materials are assessed for zoned embankment, QA testing are undertaken and that the dam embankment is constructed and compacted as per the design specification.

10.0 SURVEY MONITORING SCHEME AND RECOMMENDATIONS

The Contractor shall supply and install:

• Three (3) water level indicators or graduated posts within the 3 ponds to measure their water levels.

• Three (3) Vibratory Piezometers with a data logger should be installed at three different embankments. The preferred location selection and installation can be undertaken at the end of pond construction and before starting of operation.

• Nine (9) number of ‘Bench Marks’ on all sections of the embankments. Distribution of 9 bench marks are as follows:

- 3 on the crest of 3 boundary embankments of Pond 3

- 1 on the crest of intermediate embankment between Pond 3 and Pond 2

- 2 on the crest of 2 boundary embankments of Pond 2

- 1 on the crest of intermediate embankment between Pond 2 and Pond 1

- 2 on the crest of 2 boundary embankments of Pond 1.

It is recommended that the ponds’ water levels and x, y, z positioning data for each of the ‘9 Bench Marks’ should be surveyed monthly from their construction to the end of service period. Irregularities in monitoring data and or excessive variation of data from their previous reading should be notified, analysed, reported and undertaken necessary maintenance or remediation works.

It is recommended that the ponds and embankments should thoroughly be inspected by an experienced geotechnical engineer on fortnightly basis. The first visit can be after 0.5 m of water filling at the pond. After second visit, the frequency of the site inspection can be assessed. During field inspection, if any symptoms of structural failure of embankments are observed, maintenance and remedial works should be undertaken immediately.

It is recommended that if any symptoms of structural failure of embankments are observed by the operation crew at the site, they should immediately notify and seek advice from an experienced geotechnical engineer.


11.0 LIMITATION OF USE

The facts reported in this document are directly relevant only to the ground at the place where, and time when, the investigation was carried out and are believed to be reported accurately. Given the limited number of field and laboratory testing carried out with respect to the overall site area, variations between investigation locations is likely and ground conditions different to those presented in this report may be present within the subject site area. The risk associated with this variability and the impact it will have on the proposed development should be carefully considered.

If the above mentioned client, its subcontractors, agents or employees use this factual information for any other purpose for which it was not intended, then the client, its subcontractors, agents or employees does so at its own risk and Local Geotechnics will not and cannot accept liability in respect of the advice, whether under law of contract, tort or otherwise.

Any interpretation or recommendation given in this report is based on judgement and experience and not on greater knowledge of the facts reported. Local Geotechnics does not represent that the information or interpretation contained in this report addresses completely the existing features, subsurface conditions or ground behaviour at the subject site.

12.0 REFERENCES

Australian Standard AS1170.4-2007, “Earthquake Actions in Australia”. Australian Standard AS 1726-2017 "Geotechnical Site Investigations". Australian Standard AS 3798-2007, "Guidelines on Earthworks for Commercial and Residential Developments". Standards Australia, Hand Book HB 160-2006 "Soil Testing". AS 1289.5.3.1 AS 1289.5.7.1 AS 1289.5.1.1

APPENDIX A DRAWINGS OF EVAPORATION PONDS

100m

52m

93m

108m

25m

86m

(Varies)

91m

(Varies)

143m

(Varies)

A

A

B

B

C

C

289m

A

A

A

A

A

A

6m

5.5m

6m

5m

3.5m

EXISTING GROUND

@ 385mRL

0m 20m 40m 60m 80m 100m

SCALE

N

D

D

A

A

6.0m

6.0m

5.0m

3.5m

POND 3

WATER LEVEL @ 375mRL

POND 2


POND 1


A

A

A

A

42m

A

A

FLOOR Varies Between

373 & 374mRL


377 & 380mRL


381 & 383mRL

26m

Vibratory

Peizometer

PLAN

CONDITIONS OF USE


CONSTRUCTION ISSUE

6m 6m 5.5m

26m

EXISTING

GROUND

EXISTING

GROUND

2m High Dam Embankment

5m3.5m

1.25m

1m

1.25m

NSL

(NSL@Maximum Practicable

Horizontal Level)

5m 4.5m

0.5m 0.5m

2%

Water Level

Dam Crest Level

UPSTREAM

Varies, 1m to 4m

1m

DOWNSTREAM

TRENCH

DRAIN

Sandy/Silty/Gravelly CLAY

(Maximum Size 100mm)

General Fill (Maximum Size 200mm)

(Zone 1 material can be used too, if required)

KEY

NSLNSL

1

:

2

.

5

1

:

3

0m 1m 2m 3m 4m 5m

SCALE

Dam Crest

6m

2m

NSL = Natural Surface Level

1

:

1

.

5

1

:

3

1

:

2

.

5

1

:

2

.

5

0.5m

Zone 2

1m

Zone 1

0.5m

0.5m

1.5m 4.75m

Zone 1

Natural Contour varies

within Pond 1 to Pond 3

0.75m

SECTION AA

CONDITIONS OF USE


CONSTRUCTION ISSUE

Water Level

Dam Crest Level

Varies, 4m ~1m

2%

Water Level

0.75m

1.5m

18.5m 6m

6m

5m

3m

20m 6m

1.5m

8m

7.25m

1m

8m

KEY

382mRL

NSL Varies from

374 to 373mRL

375mRL

UPSTREAM

DOWNSTREAM






1

:

3

1

:

2

.

5

58m

EXISTING

GROUND

EXISTING

GROUND

0m 2.5m 5m 10m 20m

SCALE

Dam Crest


1

:

3

1

:

1

.

5

381mRL

Zone 2

15m 9m

NSL

@Maximum Practicable

Horizontal Level

1m

Zone 1

377mRL

1

:

1

.

5

0.5m

0.5m

0.75m

374mRL

NSL

NSL Varies from

377 to 380mRL

SECTION BB

CONDITIONS OF USE


CONSTRUCTION ISSUE

42m

0.75m 4.75m

1.5m

11m

5.5m 12.5m 6m 12m 6m

1.5m

5m

KEY

1

:

2

.

5

1

:

3

2%

Water Level

Dam Crest Level

Varies 3m~

1m

1m



DOWNSTREAM

UPSTREAM




0.5m

4m

EXISTING

GROUND

0m 2m 4m 6m 8m 10m

SCALE

EXISTING

GROUND

384mRL

385mRL


381mRL

Water Level

1

:

1

.

5

1

:

3

6m

Dam Crest

1

:

1

.

5

385mRL

NSL, Varies from

380 to 379mRL

1m

1m

Zone 2 Zone 1

380mRL

NSL@ Maximum

Practicable Horizontal Level

0.5m

0.75m

NSL, Varies from

381 to 383mRL

381mRL

SECTION CC

CONDITIONS OF USE


CONSTRUCTION ISSUE

5m 6m 6m

20m 6m 15m 12.5m 6m 6m 5m

17m 135m 41m 130m 30.5m 120m

374

375

376

377

378

379

380

381

382

383

384

385 mRL

1

2.5

1

3

1

2.5

1

3

1

3

1

2.5

1

2.5

SECTION AA SECTION BB SECTION CC

2m

8m

2m

0m 4m 8m 12m 16m 20m

SCALE

30m 40m

3.5m

385mRL

WL@384mRL

WL@381mRL

WL@375mRL

373

373mRL 374mRL

377mRL

380mRL

381mRL 383mRL

5m

NSL Varies

373 to 374mRL

NSL Varies

377 to 380mRL

NSL Varies

381 to 383mRL

SECTION DD

CONDITIONS OF USE


CONSTRUCTION ISSUE

APPENDIX B EMBANKMENT STABILITY ASSESSMENT MODELS

LGK8492019D_Design Report - Battler Evaporation Pond_Rev1

Slope Stability Analysis Results

Figure B1. Section AA- Steady State Condition


Figure B2. Section BB- Steady State Condition


Figure B3. Section CC- Steady State Condition

Corner Marvel Loch Southern Cross Road and Project ...€¦ · and Expansion of Open Pit Mining at...

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