Construction Report
Process Dam and Raw Water Dam, Jaurdi Gold Project,
Beacon Minerals Pty Ltd
Compiled by - Darren Gaby
Registered Manager Jaurdi Gold Project Beacon Minerals Pty Ltd
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Contents
Introduction ... 3
Safety ... 3
Site Preparation ... 4
Design / Control ... 4
Properties of Fill Material ... 5
Dam Construction ... 8
Machinery Used ... 8
Zone 2 ... 8
Zone 1 ... 9
Roadway ... 9
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Introduction
This report outlines the methods used to construct the process water and the raw water dams at the Jaurdi Gold Project, see completed dams in Image 1.
The Jaurdi Gold Project is subject to Department of Water and Environment Regulation (DWER) Works Approval Number W6150/2018/1 dated 05/09/2018.
As per this Works Approval Beacon must install and undertake the works for the infrastructure and equipment as per the conditions of the Works Approval, specifically:
- Install a 4500m3 capacity raw water dam and install a 5500m3 capacity process dam lined with HDPE or compacted clay lined to achieve a permeability of less than 1x10-9 m/s with a thickness no less than 300mm as shown in Schedule 1 figure 3 of the Works Approval.
Beacon Minerals performed all the works in house with their open pit department during a break in the Lost Dog open pit mining programme.
Suitable clay was identified by sites geologists and stockpiled during an earlier mining campaign in the Lost Dog pit. Gravel and zone 2 material was sourced from the excavation of the storm water dam.
Earthworks commenced on the 20th November 2018 and concluded in January 2019.
Image 1: Raw and Process Water Dams on 18/7/2019
Safety
No accidents or incidents occurred during the construction of the dams.
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Site Preparation
On the 20th November 2018 works began on the process and raw water dam.
Vegetation was scrubbed and 300mm of topsoil was removed and trucked to the dedicated topsoil stockpile to the east of the dams. The scrubbed vegetation was trucked to the dedicated mulch stockpile to the north of the Jaurdi ROM pad.
Image 2: Removing topsoil on 26/11/18.
Design / Control
Design parameters for the dams were taken from the Scope of Works for the
Embankment Construction document for the Lost Dog In-Pit Tailings Storage Facility prepared by Chris Lane of L&MGSPL.
The design for the Raw and Process dams were completed by Beacon Minerals Surveyor Steve Rogers using 3D modelling software Surpac.
Design Criteria used –
• Located within the designated clearing footprint
• Batters - 1 in 6
• Clay lining - 3m thick
• Volume - 5,500m3 capacity to the 1m free board
• Raw Dam water level 0.5m higher than process dam water
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Image 3: Raw and Process Water Dam Design
Surveying was performed by Beacon Minerals Surveyor Steve Rogers and assisted by Darren Gaby using an RTK Trimble GPS. All survey was performed in MGA94 and to +/- 50mm tolerance.
Properties of Fill Material
Zone 1 material (clay) was mined from the Lost Dog pit in July 2018 and stockpiled on the east side of the mine ROM pad for dam building purposes. All material used met the requirements set out in Table 2-1.
*Sourced from the Scope of Works for the Embankment Construction document for the Lost Dog In-Pit Tailings Storage Facility prepared by Chris Lane of L&MGSPL
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Image 4: Clay material being mined - Lost Dog pit Oct 2018.
Zone 2 material was sourced from the sites storm water dam which is situated in the south west corner of mining tenement M15/529.
All material used met the requirements set out in Table 2-2.
*Sourced from the Scope of Works for the Embankment Construction document for the Lost Dog In-Pit Tailings Storage Facility prepared by Chris Lane of L&MGSPL
The Base Course Materials were sourced from the storm water dam upper levels and part of the layer was trucked in from the MLG gravel pits which are located 10 km’s south of the project.
All material used met the requirements set out in Table 2-3.
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*Sourced from the Scope of Works for the Embankment Construction document for the Lost Dog In-Pit Tailings Storage Facility prepared by Chris Lane of L&MGSPL
Image 5: Jaurdi Gold Project on 18th July 2019.
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Dam Construction Machinery Used
Works were undertaken by the sites open pit department using a Hitachi 90t hydraulic excavator to load Caterpillar 45t articulated dump trucks to transport the material to the dams.
The auxiliary equipment used were a Caterpillar 14H grader, Caterpillar 825 compactor, Cat 45t articulated water truck and a Caterpillar D10R dozer.
Both the Raw and Process water dams were constructed at the same time and the same methods of construction were applied.
Zone 2
Zone 2 material was paddock dumped within the demarcated area then pushed out with the dozer in 300mm benches. The watercart then applied water to ensure the material had enough moisture before the grader was used to smooth the running surface for the trucks. When confirmation from the surveyor was received that the bench was on level 4-5 passes of the compactor was used to achieve the desired compaction.
Although minimal, boulders greater than 300mm in size were picked up by the loader and hauled to the sites waste dump.
Image 6: Zone 2 being compacted, dozer pushing out a 300mm lift.
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Image 7: Process Dam zone 2 batters to design.
Zone 1
Once zone 2 progressed two Zone 1 material lifts was paddock dumped within the demarcated area then pushed out with the dozer in 300mm benches. The watercart then applied water to ensure the material had enough moisture before the grader was used to smooth the running surface for the trucks. When confirmation from the surveyor was received that the bench was on level 4-5 passes of the compactor was used to achieve the desired compaction.
The excavator and grader were used to cut the batter of wall to the final slope.
Roadway
On completion of the embankment a road was sheeted with 300mm of gravel around the crest of the dams to allow safe access for vehicles. A safety bund was installed on both the inside and outside of the road.
This report does not include the installed piping or associated infrastructure.
