Amendment Notice 2
Licence Number L8412/2010/2
Licence Holder Regis Resources Limited
ACN 009 174 761
File Number: 2012/006893
Premises Moolart Well
Mining Tenements M38/354, M38/498, M38/499, M38/500 and M38/589
LAVERTON WA 6440
Date of Amendment 27/05/2019
Amendment The Chief Executive Officer (CEO) of the Department of Water and Environmental Regulation (DWER) has amended the above Licence in accordance with section 59 of the Environmental Protection Act 1986 (EP Act) as set out in this Amendment Notice. This Amendment Notice constitutes written notice of the amendment in accordance with section 59B(9) of the EP Act.
Tim Gentle Manager – Resource Industries an officer delegated under section 20 of the Environmental Protection Act 1986 (WA)
Licence: L8412/2010/2
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Definitions and interpretation
Definitions In this Amendment Notice, the terms in Table 1 have the meanings defined. Table 1: Definitions
Term Definition
ACN Australian Company Number
AER Annual Environment Report
Amendment Notice refers to this document
Category/ categories of Prescribed Premises as set out in Schedule 1 Categories/ Cat. of the EP Regulations
CEO means Chief Executive Officer. CEO for the purposes of notification means: Director General Department Administering the Environmental Protection Act 1986 Locked Bag 10 Joondalup DC WA 6919 [email protected]
Delegated Officer an officer under section 20 of the EP Act
Department means the department established under section 35 of the Public Sector Management Act 1994 and designated as responsible for the administration of Part V, Division 3 of the EP Act.
DWER Department of Water and Environmental Regulation
EPA Environmental Protection Authority
EP Act Environmental Protection Act 1986 (WA)
EP Regulations Environmental Protection Regulations 1987 (WA)
Existing Licence The Licence issued under Part V, Division 3 of the EP Act and in force prior to the commencement of and during this Review
Licence Holder / Regis Resources Limited Licensee
Licence: L8412/2010/2
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Noise Regulations Environmental Protection (Noise) Regulations 1997 (WA)
Prescribed has the same meaning given to that term under the EP Act. Premises
Premises refers to the premises to which this Decision Report applies, as specified at the front of this Decision Report.
Risk Event as described in Guidance Statement: Risk Assessment
Licence: L8412/2010/2
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Amendment Notice This amendment is made pursuant to section 59 of the Environmental Protection Act 1986 (EP Act) to amend the Licence issued under the EP Act for a prescribed premises as set out below. This notice of amendment is given under section 59B(9) of the EP Act. This notice is limited only to an amendment for Category 5. No changes to the aspects of the original Licence relating to Categories 73, 85 and 89 have been requested by the Licence Holder. The following guidance statements have informed the decision made on this amendment Guidance Statement: Regulatory Principles (July 2015) Guidance Statement: Setting Conditions (October 2015) Guidance Statement: Decision Making (February 2017) Guidance Statement: Risk Assessment (February 2017) Amendment description On 21 December 2018, the Regis Resources Limited (Licence Holder) submitted an application to amend the Moolart Well Gold Project licence L8412/2010/2. The Licence Holder applied for the following changes: Approval for the construction and operation of a new in-pit Tailings Storage Facility (TSF) at the Stirling pit on tenement M38/499 and M38/500; and Installation of six monitoring bores (constructed to a depth of 80m) around Stirling pit and the addition of these monitoring locations on the licence; Bores to be added: RRLMWMB045, RRLMWMB046, RRLMWMB047, RRLMWMB048, RRLMWMB049, RRLMWMB050. To date tailings have been deposited into an above ground TSF at the Moolart Gold Project. The development of the Stirling in-pit TSF will provide continued tailings storage for Moolart Well when the existing TSF has reached capacity. Stirling TSF will contain processed tailings from various open pits at Moolart Well, Gloster, Dogbiter/Coopers, Anchor and the as yet approved Petra pits. Stirling pit has an approximate rim area of 31 ha, and a length south-north of approximately 1km. The pit has a maximum depth of approximately 75m. It is expected that approximately 10 million tonnes (Mt) of tailings will be deposited into the in-pit TSF over 3-4 years. The supporting documentation has been prepared by consultants CMW Geoscience Pty Ltd and includes the full engineering design report. The supporting document stated that the design has been done in accordance with the Department of Mines and Petroleum (2013), ‘Code of practice: tailings storage facilities in Western Australia’. The location of the new Stirling TSF and the 6 new monitoring bores is shown in Figure 1 below.
Licence: L8412/2010/2
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Figure1: Location of proposed Stirling TSF and six new monitoring bores.
Licence: L8412/2010/2
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Operation of the Stirling TSF The Licence Holder’s application states that an operations manual for the TSF outlining the operating procedures, inspection criteria, monitoring, requirements and log sheets for the facility will be prepared for the Stirling TSF prior to commissioning. The operation of the Stirling TSF will be as follows;
Stage 1 (Start-up): Tailings in the form of slurry will be discharged sub-aerially via two single point discharges from the northern pit wall; Tailings deposition is to be carried out such that the supernatant pond is around the southern area of the pit; and There is an opportunity for mine waste, if available, to be used to backfill the pods in the south western and south eastern area of the TSF to reduce ponding at the base of the pit in isolated pockets.
Stage 2 (Year 1): Tailings will continue to be discharged sub-aerially via two single point discharges from the northern pit wall until the tailings level reaches nominally RL 500 m; Surface water will be removed from the TSF by a decant pump located on the pit ramp at the southern end of the pit. The decant pump will be moved up the ramp as tailings and water levels rise.
Stage 3 (Year 2): Tailings discharge will be undertaken from the northern boundary with additional deposition from the south west corner of the pit. This will facilitate the migration of the supernatant pond towards the central east location in the pit. As the supernatant pond migrates towards the central east location of the TSF, the decant pump will be stationed on a floating pontoon or similar.
Stage 4 (Year 3): The tailings discharge point will be moved along both the northern and southern boundary to ensure the even build-up of a tailings beach sloping gradually towards the floating pontoon decant at the central east location of the SPTSF. An embankment will be constructed on the northern boundary with compacted mine waste to raise the pit level at the northern end of the pit (between RL526 and RL 530m).
As outlined above an embankment raise is proposed in the third year of operation of the Stirling TSF. The estimated tailings storage areas, volumes and storage capacity for the TSF are summarised in Table 2 below.
Table 2: Estimated Tailings Storage volumes (CMW Geosciences Pty Ltd, 2019).
Licence: L8412/2010/2
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Tailings is planned for discharge alternatively from each end of the pit to optimise beaching length and decant drainage as well as for maximum evaporation drying.
Water recovery system Surface water will initially be removed from the TSF by a decant pump deployed from the pit ramp at the southern end of the pit. Return water will be pumped directly to the process plant for reuse. The decant pump will be moved up the ramp as tailings and water levels rise. As the supernatant pond migrates towards the central east location of the TSF, the decant pump will be stationed on a floating pontoon or similar. A ramp access for pump maintenance will need to be constructed in Year 3 on the central east wall of the pit (CMW Geosciences Pty Ltd, 2019). Other approvals The Licence Holder has provided the following information relating to other approvals as outlined in Table 3. Table 2: Relevant approvals
Legislation Number Approval
RIWI Act 1914 1. GWL169314 (2) Moolart 1. Approval to extract 5,000,000kL Well for mine dewatering and dust suppression 2. GWL175982(1) Rosemont 2. Approval to extract 3. GWL182924 (1) Gloster 1,300,000kL for mineral ore processing and other mining purposes and dewatering for mining purposes and dust suppression for mining purposes 3. Approval to extract 1098750kL of water for dewatering for mining purposes and dust suppression for mining purposes.
Mining Act 1978 Mining Proposal Mining Lease 38/354, 38/498. 38/499, 38/500, 38/589 Mining proposal for the Stirling TSF has been approved after the licence holder commissioned an independent 3rd part review of the geotechnical design of the ‘saddles’ pillars that will be left between the Stirling in-pit facility and the two neighboring operations, Landcaster and Beaufort pits. The independent review concluded that the geotechnical design is appropriate and so based on this DMIRS has approved the proposal.
Amendment history Table 4 provides the amendment history for L8412/2010/2.
Licence: L8412/2010/2
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Table 3: Licence amendments
Instrument Issued Amendment
L8412/2010/2 31/03/2016 Amendment to correct the limit for the treated wastewater discharged to the irrigation area.
L8412/2010/2 24/08/2018 Amendment notice 1 – The addition of Category 6 Mine dewatering and an increase in throughput for Category 85 sewage facility.
L8412/2010/2 - This amendment. Amendment notice 2 – construction and operation of Stirling in-pit TSF and inclusion of 6 additional groundwater monitoring bores.
Location and receptors The Moolart Well Gold Project is located approximately 130km north of Laverton in the Eastern Goldfields. The Stirling pit TSF is located on Mining Leases M38/499 and M38/500, approximately 1km west of the Moolart Well plant site. Table 5 below lists the relevant sensitive land uses in the vicinity of the Prescribed Premises which may be receptors relevant to the proposed amendment. Table 4: Receptors and distance from activity boundary
Residential and sensitive premises Distance from Prescribed Premises
Banjawarn Station homestead >50km north east of the Premises.
Erlistoun Station homestead >100km south west of the Premises.
Mulga Queen (community) 55 km north east of the Premises.
Table 6 below lists the relevant environmental receptors in the vicinity of the Prescribed Premises which may be receptors relevant to the proposed amendment. Table 5: Environmental receptors and distance from activity boundary
Environmental receptors Distance from Prescribed Premises
Surface water Moolart Well is located within the northern catchment of the Western Plateau Drainage Division of the Salt Lake Surface Water Management Area; a large central inland catchment. Drainage lines in the area are relatively small resulting in slow moving sheet flow during periods of high rainfall. Sheet flow moves in a northerly direction towards a local drainage depression and eventually to Lake Wells. The closest drainage line to the Stirling open pit is approximately 200-400m to the west behind the pit diversion bund.
Groundwater Average pre-mining groundwater depth was approximately 15 meters below ground level (mbgl) with salinity measures of 1400 to 2200 mg/L (considered to be potable to brackish in the Goldfields).
Licence: L8412/2010/2
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As a consequence of pit dewatering and mill supply from bore-fields to the south and north of the mine, a large depression has resulted in the regional groundwater system. This depression is 10km long, 3km wide and up to 60m deep. On cessation of mining operations there will be slow recovery of the regional groundwater system. This recovery may be impacted by seepage from the Stirling Pit TSF. The final water level at Moolart Well is predicted to remain at 35m to 50mbgl. Therefore some of the seepage from Stirling TSF when filled to the final level with tailings will flow towards the adjacent open water filled voids (CMW Geosciences Pty Ltd, 2019). The nearest pastoral bore is located approximately 5km to the north of the proposed Stirling TSF.
Fauna Three species of conservation significant fauna have been sighted with the Duketon Gold Project area; the Australian bustard (Ardeotis australis), the Fork-tailed Swift (Apus pacificus), and the rainbow bee-eater (Merops ornatus).
Flora Two priority flora species Baeckea sp. Melita Station and Eremophila pungens occur within the area.
Risk assessment Tables 7 and 8 below describe the Risk Events associated with the amendment consistent with the Guidance Statement: Risk Assessments. Both tables identify whether the emissions present a material risk to public health or the environment, requiring regulatory controls.
Licence: L8412/2010/2
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Table 6: Risk assessment for proposed amendments during construction Risk Event Consequence Likelihood Potential Risk Reasoning Potential Potential Potential rating rating Source/Activities adverse emissions receptors pathway impacts
The distance to residential receptors is considered to be too great for dust or noise impacts Air: from construction of the Stirling Particulate No residences or TSF infrastructure to occur. The Dust matter N/A N/A N/A other sensitive Delegated Officer considers that Category 5 (fugitive receptors in close a pathway for dust / noise Processing or Construction dust) proximity. Closest emissions does not exist. beneficiation of Stirling Amenity receptor is of metallic or TSF impacts Banjawarn Any potential dust emissions can non-metallic infrastructure. Station be regulated by section 49 of the ore homestead Air: Noise EP Act. (>50km away) generated by the The provisions of the Noise operation of N/A N/A N/A Environmental Protection (Noise) equipment Regulations 1997 are also during applicable. construction
Table 7: Risk assessment for proposed amendments during operation Risk Event Consequence Likelihood Risk Reasoning rating rating Source/Activities Potential Potential Potential Potential emissions receptors pathway adverse impacts Category 5 Deposition Dust: release No residences Air: Amenity N/A N/A N/A The distance to residential receptors is Processing of tailings of particulate or other Particulate impacts considered to be too great for dust or or into Stirling matter from sensitive matter noise impacts from operation of the beneficiation in-pit TSF operation of receptors in (fugitive Stirling TSF to occur. of metallic or the TSF lift close proximity. dust) non-metallic Noise: Closest Air: Noise N/A N/A N/A The Delegated Officer considers that a ore associated receptor is generated by pathway for dust / noise emissions with the Banjawarn the operation does not exist. operation of Station of the TSF homestead equipment.
Licence: L8412/2010/2
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(>50km away) Any potential dust emissions can be regulated by section 49 of the EP Act.
The provisions of the Environmental Protection (Noise) Regulations 1997 are also applicable. Waste: Surface water Land: Direct Contamination Major Rare Medium The CMW Geosciences Design Report Overtopping of systems and discharge to of surrounding 2019 states that ‘The proposed TSF TSF causing surrounding land land with toxic has been designed such that a 1% tailings soils and metals and AEP, 72-hour duration storm event can discharge to vegetation metalloids, be temporarily stored on top of the land dissolved facility’. solids and cyanide The TSF has been designed so that affecting soil there will be a minimum of 500mm total and freeboard comprising minimum groundwater operational freeboard (vertical height quality between the tailings beach and embankment crest) of 300mm and a minimum beach freeboard of 200mm plus an allowance for the 1% AEP 72 hour event of 185mm.
Surface water will be removed from TSF by a decant pump deployed from the pit ramp at the southern end of the pit. Return water will be pumped directly to the process plant for reuse. This will help maintain the freeboard.
There is an existing flood bund that has been constructed around the eastern, southern and western sides of the stirling pit area to prevent stormwater ingress into the pit.
The Delegated Officer considers that the likelihood of this event occurring to be ‘rare’ due to the Licence Holders proposed controls. The consequence is considered to be ‘Major’. Therefore the risk rating is Medium.
Existing Condition 1.2.5 require the
Licence: L8412/2010/2
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inspection of TSF to confirm freeboard capacity on a daily basis.
Existing condition 1.2.3 also requires the Licence Holder to maintain a minimum top embankment freeboard of 300mm on all containment cells or ponds. This condition will be updated to include the in-pit TSF.
The Delegated Officer considers that existing conditions on the Licence to manage the risk of TSF overtopping are adequate. Waste: Vegetation and Land: Direct Contamination Moderate Unlikely Medium Construction of the TSF will involve Tailings and soil adjacent to discharge to of surrounding pipeline and pump installation as part of return water tailings pipeline land and land with toxic slurry and return water systems and from rupture or alignment infiltration to metals and installation of a decant at the TSF. The leaks of groundwater metalloids, pipeline corridor route will be west from pipelines Groundwater dissolved the plant along existing haul roads. solids and Construction will include the following cyanide requirements: affecting soil Pipe lines will be bunded between and the plant and TSF (i.e. bunded on groundwater the side of the existing haul roads). quality Spilled water or tailings will flow back to sumps or the Stirling Pit TSF; and The existing safety bunding around the Stirling Pit and the flood bund to the west of/around the pit area will be retained.
Inspections of the pipelines will also occur on a daily basis.
The Delegated Officer considers that the likelihood of this event occurring to be ‘unlikely’ due to the Licence Holders proposed controls. The consequence is considered to be ‘Moderate’. Therefore the risk rating is Medium.
Licence: L8412/2010/2
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Existing Condition 1.2.5 requires the inspection of TSF pipelines on a daily basis. Also existing condition 1.2.1 requires that all pipelines containing tailings, decant water etc. must be equipped with telemetry systems or with automatic cut-outs in the event of a pipeline failure and provided with secondary containment sufficient to contain any spill.
The Delegated Officer considers that existing conditions on the Licence to manage the risk of pipeline spills is adequate.
Waste: Surrounding Land: Contamination Moderate Possible Medium 1. Refer to detailed risk Leachate from vegetation Infiltration of groundwater assessment (risk event 1) below. TSF seepage. through soil potentially used Pastoral stock profile to for stock watering bores. groundwater watering purposes. Depth of groundwater Impacts on in area is on vegetation average 15mngl. Contamination of surrounding soils with metals and metalloids, dissolved solids and cyanide affecting soil and groundwater quality Waste: Decant Birds or Bats Birds or bats Cyanide Major Possible High The application documents state that pond water on drinking the poisoning water chemistry of the proposed tailings surface of TSF decant water discharge into Stirling Pit is expected to be similar to present discharge into the sites current TSF, which has a Total cyanide content of approximately
Licence: L8412/2010/2
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130mg/L. The application states ‘wide experience in the Australian mining industry demonstrates that cyanide released with tailings into tailings storages at a concentration of 180mg/L to 200mg/L total cyanide rapidly breaks down to a cyanide content of 20mg/L to 40mg/L by the time water is picked up in the decant pumping system for recovery to the plant processing circuit. This is usually over a time factor of 20 to 40 hours’ (KH Morgan 2018). As the groundwater and tailings are of relatively low salinity the shallow water in the decant pond is likely to be attractive to birds (or bats at night) with consequent risk of wildlife poisoning.
However, research has indicated that gold processing tailings with residual WAD-CN in solution above 50 mg/L with a salinity of less than 50,000 present a risk to wildlife health (Adams, 2008). Further research has shown that, in the absence of systematic surveys by appropriately trained personnel, bird deaths from cyanide poisoning may occur at gold mines without mine personnel being aware of it (Donato, 2016).
The Delegated Officer considers that there is still a significant risk of wildlife poisoning and that the likelihood of this event occurring to be ‘Possible’ and the consequence to be ‘Major’. Therefore the overall risk rating is High.
This is a site-wide issue and the Delegated Officer has determined that it will be dealt with through a separate DWER initiated amendment.
Licence: L8412/2010/2
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Detailed Risk Assessment
1. Risk Event: Seepage of leachate from tailings discharged into Stirling pit.
Description of Risk Event Tailings will be deposited into the Stirling pit on a continuous basis. Seepage of tailings leachate into the surrounding groundwater may occur over time with the potential to impact on the groundwater users.
Identification and general characterisation of emission Tailings are a waste product of the processing of ore. They contain metals and metalloids such as arsenic, cadmium, chromium, mercury and lead which are hazardous to the environment as well as toxic to human and animal life. The proposed tailings to be deposited within Stirling Pit is expected to be approximately 50% solids and has been assigned a hazard rating of Low, Category 3, based on the classification criteria determined by consultants CMW Geosciences Pty Ltd and based on Department Mines, Industry Regulation and Safety (DMIRS) guidelines. The Licence Holder has advised that the tailings chemistry of the proposed tailings discharge into Stirling Pit is expected to be similar to the former tailings discharged into the sites current TSF. The tailings is expected to have a pH value between 7 - 8 and total dissolved solids of 5200 mg/L. The tailings solids chemistry is listed below in Table 9. Decant water is expected to have a pH range between 7.5 – 9.5 and WAD CN levels between 30-50mg/L. Table 9: Expected tailings chemistry (KH Morgan & Associates, 2019) Parameter Measurement unit Conductivity 5100 s/cm pH 7-8 - Total dissolved solids 5200 Calcium 180 Magnesium 43 Sodium 800 Bicarbonate 42 Carbonate 13 Total alkalinity 43 Sulphate 480 Silicon 9 Chloride 1100 mg/L Manganese 0.01 Nitrate 150 Copper 2 Arsenic <0.05 Cadmium <0.01 Chromium <0.01 Mercury <0.00005 Zinc 18 Total cyanide 130
A composite tailings sample comprising 75% Gloster Pit ore and 25% Wellington/Beaufort ore was submitted to MPL Laboratory for analyses to Australian Standard Leaching Procedure (ASLP4439.3). The laboratory results were evaluated and reported by SRK Consulting.
Licence: L8412/2010/2
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Conclusions drawn by SRK Consulting on the laboratory test work indicate that the tailings are Non Acid Forming (NAF) with an excess of neutralising (ANC) capacity. Trace concentrations were close to standard analytical detection limits and these levels conform to ANZECC guidelines for livestock drinking water requirements in the mildly acid to mildly alkaline leaching conditions test. The general conclusion from the leaching tests is that Stirling Pit tailings present low risk for acid and metalliferous drainage (SRK Consulting, 2019).
Description of impacts from the increased emission Seepage from the in-pit tailings facility has the potential to contaminate the surrounding groundwater and any groundwater dependent ecosystems. Vegetation death through groundwater mounding or contamination with metals and metalloids may occur. Average groundwater depth is approximately 15mbgl with salinity measures of 1400 to 2200 mg/L (considered to be potable to brackish in the Goldfields). There are no public drinking water supply areas within the project area. Groundwater is predominantly used for mining and stock watering purposes. The closest pastoral bore is approximately 5km south west of the proposed Stirling TSF. There are no known groundwater-dependent ecosystems, stygofauna or troglofauna of conservation significance within the project area. Interaction between surface water systems and groundwater in the area is unknown, although the depth to groundwater (15 – 60 mbgl) suggests there is limited interaction. The closest ephemeral surface water drainage line is approximately 300m away from the Stirling pit edge. As a consequence of pit dewatering and mill supply from bore-fields to the south and north of the mine, a large depression has resulted in the regional groundwater system. This depression is 10km long, 3km wide and up to 60m deep. On cessation of mining operations there will be slow recovery of the regional groundwater system. This recovery may be impacted by seepage from the Stirling Pit TSF. The final water level at Moolart Well is predicted to remain at 35m to 50mbgl. A numerical seepage model (KH Morgan and Associates, 2019) and an independent 2- Dimensional numerical groundwater model (EMM Consulting Pty Ltd, 2019) was carried out to determine the amount of seepage expected from the proposed Stirling TSF. Both models predicted approximately 200,000m3 of leachates will drain form the tailing pile during the proposed 3.7 years of deposition into the surrounding rock, and approximately 400 ML will seep out over the following 100 years.
The models also predicted that groundwater flow will be predominately towards the east while the neighbouring pit (Lancaster Pit) remains an open void due to the major dewatering depression encompassing the mining area. Lancaster Pit is expected to be a permanent groundwater sump for drainage from Stirling Pit. Evaporation from Lancaster Pit will reduce the volume of leachate for penetration into the groundwater system (Figure 3).
Tailings seepage water is estimated to achieve dispersion and dilution to regional groundwater water quality levels (total salinity, pH and trace metal quality) outward from the mixing zone shown on Figure 4. It is expected that mixing zone will have no impact on other groundwater users in the area as it is expected that impacted groundwater will flow towards the surrounding mine voids and evaporate. The closest pastoral bore is located approximately 5 kilometres north of Stirling Pit.
Groundwater mounding due to leachate from the TSF is not expected to occur due to the large depression in the local groundwater system due to dewatering.
Licence: L8412/2010/2
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Figure 3. Expected flow direction of leachate from Stirling TSF.
Licence: L8412/2010/2
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Figure 4: Expected Stirling TSF seepage mixing zone.
Licence: L8412/2010/2
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Criteria for assessment Whilst there are no applicable guidelines for specific water quality of the groundwater the ANZECC 2000 guidelines for irrigation and livestock drinking water provide some criteria for comparison.
Licensee controls Tailings deposition will initially be into the northern end of the pit from single point discharges. The tailings discharge point will also be from the south-west corner boundary during the next stage to ensure the even build-up of a tailings beach and the migration of the supernatant pond to a more central location in the pit. Surface water that is currently within the pit will be removed prior to deposition. Return water will be pumped directly from the decant pond to the process plant for reuse. The decant pump will be moved up the ramp as tailings and water levels rise. The Licence Holder’s application states that based on a 3Mtpa and 50% solids, a water return capacity of 342 t/hr (8.219 t per day) will be provided. The anticipated average annual water return for an in-pit facility in the NE goldfields can be expected to be at least 60% of the slurry water inflow. Drainage holes exist on the western and end walls of the pit. These drainage holes will be plugged to ensure leachate and tailings will be prevented from seeping into surrounding rock. Monitoring of groundwater level and quality currently occurs onsite at monitoring bores surrounding the current TSF. The Licence Holder is proposing to construct an additional 6 monitoring bores (to a depth of 80m) around the perimeter of the new in-pit TSF to monitor impacts to groundwater. Standing water level (SWL) and water quality parameters will be monitored on a quarterly basis and presented to DWER in the projects annual report. The following parameters will be monitored; Total cyanide, WAD cyanide, pH, Electrical conductivity, Total Dissolved Solids (TDS), AS, HG, Ni, Fe, Pb, Na, K, Ca, Mg, Zn, Cu, Cr, NO3, SO4, HCO3, CO3, CI.
Consequence If seepage of the Stirling in-pit TSF occurs, then the Delegated Officer has determined that the impact of seepage to surrounding groundwater will cause mid-level on-site impacts. Therefore, the Delegated Officer considers the consequence of seepage to be moderate.
Likelihood of Risk Event The likelihood of this Risk Event having an impact on local groundwater users is unlikely due to the Licence Holders controls, distance to nearest pastoral bore and the fact that the neighboring Lancaster pit will act as a groundwater sump for drainage from Stirling Pit. Leachate tests also indicating that possible seepage from the proposed Stirling TSF will meet ANZECC guidelines for livestock drinking water under mildly acid to mildly alkaline leaching conditions. The Delegated Officer has therefore determined that likelihood of impact is unlikely.
Overall rating of Risk Event The Delegated Officer has compared the consequence and likelihood ratings described above with the risk rating matrix outlined in Guidance Statement: Risk Assessments and has determined that the overall rating for the risk of seepage from the Stirling TSF as medium.
Licence: L8412/2010/2
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Decision Based upon the applicant’s supporting documentation, the Delegated Officer has determined that the construction of the new Stirling in-pit TSF presents a low risk to the environment. Construction conditions and compliance reporting have been included as new conditions to the Licence as shown below; - Condition 1.2.12 has been included as a new condition for the construction of the new in-pit TSF - Conditions 1.2.13 and 1.2.14 has been included as new conditions requiring the Licensee to provide engineering certification to DWER within 30 days following the completion of each TSF construction stage. - Condition 1.2.15 has been included as a new conditions requiring the Licensee to operate all TSFs onsite in accordance with the current version of the TSF operating manual. This condition has been added for consistency with similar operations. - Maps indicating the location of the new TSF and new monitoring bores have also been added to the licence. Based upon the applicant’s supporting documentation, the Delegated Officer has determined that the operation of the new Stirling in-pit TSF presents a medium risk to the environment due to the potential impact from seepage and the possibility of discharge of tailings due to pipeline rupture or overtopping of the TSF. The Delegated Officer has determined that these risks are acceptable subject to amendments to the existing regulatory controls in the Licence as shown below; - Condition 1.2.2 has been amended to include the Stirling in-pit TSF as containment infrastructure for tailings. This condition has also been amended to ensure a minimum freeboard of 300mm is maintained to ensure overtopping of the pit does not occur. - Condition 1.2.3 has been amended to include all containment infrastructure so the Stirling in-pit TSF is included in the freeboard requirement. - Condition 3.4.1 has been amended to include the six new groundwater monitoring bores surrounding the Stirling pit to monitor impacts to groundwater by seepage. Additional parameters to be monitored have also been added to this condition (Sb, Co, Mn and U), this is consistent with the Licence Holder’s other site Garden Well. Existing condition 4.2.1 will require the Licensee to provide DWER with these monitoring results on an annual basis within their AER. The Delegated officer has determined that existing conditions 1.2.1 (pipeline management), 1.2.3 (freeboard), 1.2.5 (inspections) adequately manage the risk of pipeline rupture and TSF overtopping and do not require amendment. DWER has identified the potential for cyanide poisoning of birds or bats which come into contavy with the TSF decant pond as a site-wide risk requiring management controls. This issue will be addressed in a separate amendment Licence Holder’s comments The Licence Holder was provided with the draft Amendment Notice on 14 May 2019. The Licence Holder responded on the 25 May 2019 asking for the remainder of the comment period to be waived as they have no comments and wish the licence amendment to be issued as soon as possible. Amendment
1. Licence L8412/2010/2 is amended by the insertion of Condition 1.2.12
Licence: L8412/2010/2
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1.2.12 The licence holder must construct the infrastructure listed in Table 1.2.5, in accordance with; the corresponding design and construction requirement and at the corresponding infrastructure location; as set out in Table 1.2.5. Table 1.2.5 Design and construction requirements Infrastructure Design and construction requirement Infrastructure location Stirling in-pit Installation of slurry and return water Sitrling in-pit TSF location Tailings Storage pipeline systems, pump and decant as depicted in Schedule 1: Facility(TSF) structure Maps, Map of Stirling in-pit Stages 1 to Sealing of pit wall drainage holes TSF Stage 3
Installation of monitoring bores to a Monitoring bore indicative depth of 80 m RRLMWMB045, locations as shown in RRLMWMB046, RRLMWMB047, Schedule 1: Maps, Map of RRLMWMB048, RRLMWMB049, monitoring locations RRLMWMB050 Stirling in-pit Construction of an embankment on the as depicted in Schedule 1: Tailings Storage northern boundary of Stirling pit using Maps, Map of the location Facility(TSF) compacted mine waste to raise the pit level of Stirling in-pit TSF Stage 4 at the northern end of the pit (between RL526 and RL 530m).
2. Licence L8412/2010/2 is amended by the insertion of Condition 1.2.13
1.2.13 The licence holder must within 30 days of each item of infrastructure required by condition 1.2.12 being constructed: (a) undertake an audit of their compliance with the requirements of condition 1.2.12; and (b) prepare and submit to the CEO an audit report on that compliance.
3. Licence L8412/2010/2 is amended by the insertion of Condition 1.2.14 1.2.14 The report required by condition 1.2.13, must: (a) be certified by a qualified professional engineer that each item of infrastructure listed in Table 1.2.5 meets the corresponding specifications and at the locations set out in Table 1.2.5 and has been constructed with no material defects; and (b) be signed by a person authorised to represent the licence holder and contain the printed name and position of that person within the company.
4. Licence L8412/2010/2 is amended by the insertion of Condition 1.2.15 1.2.15 The Licence Holder shall operate the TSFs onsite in accordance with the current version of the TSF operating manual, at all times.
Licence: L8412/2010/2
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5. Licence L8412/2010/2 is amended by the insertion of the following map in Schedule 1: Maps - Map of Stirling in-pit TSF
Map of the location of the Stirling in-pit TSF.
Licence: L8412/2010/2
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6. Licence L8412/2010/2 is amended by the insertion of the following map in Schedule 1: Maps - Map of monitoring locations
Licence: L8412/2010/2
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7. Condition 1.2.2 of the Licence is amended with the insertion of the text shown in red underline below;
1.2.2 The Licensee shall ensure that tailings, decant water and effluent are only discharged into containment cells and ponds or mine voids with the relevant infrastructure requirements and at the locations specified in Table 1.2.1 and identified in Schedule 1.
Table 1.2.1 Containment infrastructure Containment point Material Infrastructure requirements reference Stirling in-pit Tailings Tailings An operational freeboard (vertical height Storage Facility between the tailings beach and the lowest part of the embankment crest) of at least 300mm must be maintained at all times. Tailings storage Tailings Clay lined to achieve a permeability of at facility least <10-9 m/s Process water pond Decant Water HDPE lined to achieve a permeability of <10-9 m/s
Primary oxidation Effluent from WWTP HDPE lined to achieve a permeability of pond <10-9 m/s Secondary oxidation Effluent from WWTP HDPE lined to achieve a permeability of pond <10-9 m/s South, Central and Mine dewater A minimum vertical freeboard of 15m must North pits be maintained below the lowest crest level at all times.
8. Condition 1.2.3 of the Licence is amended with the insertion of the text shown in red underline and the deletion of the text shown in strikethrough below;
1.2.3 The Licensee shall manage containment infrastructure cells and ponds in Table 1.2.1 such that a minimum top of embankment freeboard of 300mm or a 1 in 100 year/72 hour storm event (whichever is greater) is maintained.
9. Condition 1.2.4 of the Licence is amended with the insertion of the text shown in red underline below;
1.2.4 The Licensee shall manage above ground TSFs such that: (a) a seepage collection and recovery system is provided and used to capture seepage from the TSF; and (b) seepage is returned to the TSF or re-used in process
10. Condition 3.4.1of the Licence is amended with the insertion of the text shown in red underline below;
3.4.1 The Licensee shall undertake the monitoring in Table 3.4.1 according to the specifications in that table and record and investigate results that do not meet any target specified.
Table 3.4.1: Monitoring of ambient groundwater quality Monitoring Parameter Limit Units Averaging Frequency point reference period and location MB01 Standing 4 m(AHD) Spot sample Quarterly
Licence: L8412/2010/2
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MB02 water level MB03 pH1 - - MB04 Electrical µS/cm MB05 conductivity RRLMWMB045 Total mg/L RRLMWMB046 dissolved RRLMWMB047 solids RRLMWMB048 Arsenic RRLMWMB049 Antimony RRLMWMB050 (Sb) Mercury Nickel Iron Lead Sodium Potassium Calcium Magnesium Zinc Copper Chromium Cobalt (Co) Manganese (Mn) Uranium (U) Nitrate (NO3) Sulfate (SO4) Bicarbonate (HCO3) Carbonate (CO3) Chloride Total cyanide2 Weak- acid 0.5 dissociable cyanide2
Licence: L8412/2010/2
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Appendix 1: Key documents
Document title In text ref Availability 1 Licence L8412/2010/2 L8412/2010/2 accessed at www.dwer.wa.gov.au 2 Licence Amendment application – Moolart Application DWER records (A1752271) Well, Regis Resources Limited, 21 December 2018. Includes attachments 3 Stirling Pit Tailings Storage Facility, CMW DWER records (A1773999) Moolart Well Gold Mine WA Design Geosciences Report, Regis Recourses Limited, Ref. Pty Ltd, 2019 PER2018-0241AB Rev 1, CMW Geosciences Pty Ltd, 8 March 2019. 4 Amendment to Licence L8412/2010/2, Application DWER records (A1774000) Clarification of items raised in letter dated 1 February 2019 (letter and attachments), Regis Resources Limited, 19 March 2019 5 Proposed Tailings Deposition Stirling KH Morgan and Open Pit, Moolart Well Gold Mine, Regis Associates, Resources Limited, 10 March 2019 2019 6 Stirling Pit Tails Study, 2-Dimensional EMM Consulting Numerical Model, EMM Consulting Pty Pty Ltd, 2019 Ltd, 20 February 2019. 7 Moolart Well Tailings Materials SRK consulting, Characterisation, SRK consulting,7 March 2019 2019 8 Adams MD, 2008, Cyanide ecotoxicity at Adams, 2008 - hypersaline gold operations, MERIWA report no273, Volume I – Phase I (Preliminary Investigation), Volume II– Phase II (Definitive Investigation), Volume III – Appendices to Phase II, August (Minerals and Energy Research Institute of Western Australia: Perth) 9 Donato D and Overdevest ND, 2016, Donato, 2016 - Approaches to Cyanide Code Compliance for Tailings Storage Facilities, Chapter 13 in Adams MD (Editor) Gold Ore Processing – Project Development and Operations 2nd edition, Elsevier Science. 10 DER, October 2015. Guidance Statement: N/A accessed at www.dwer.wa.gov.au Setting conditions. Department of Environment Regulation, Perth. 11 DER, November 2016. Guidance Statement: Risk Assessments. Department of Environment Regulation, Perth. 12 DER, November 2016. Guidance Statement: Decision Making. Department of Environment Regulation, Perth.
Licence: L8412/2010/2
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