Environmental guidelines for the management of small tailings storage facilities

Small TSFs are those which fit the criteria (S) below, where S = Small and L= Large:

The height of the embankment is determined from Sits maximum height above the natural surface.

Tailings are only classified as BLLC tailings if they do not exceed, or are not predicted to exceed, the level of contaminants as specified in the definition of contaminated tailings in Appendix I.

All TSFs storing, or predicted to store, contaminated tailings as specified in the definition of contaminated tailings in Appendix I must meet the requirements set out in the MTSF 2004, regardless of size or capacity.

A work plan must be lodged and approved before construction or operation of a TSF can commence. Where a proposal includes an additional, extended or changed TSF (such as the addition of a lift to a pre-existing TSF) on an existing site, the operators must submit an appropriate work plan variation.

Often the TSF proposal will be part of a larger mining or quarrying proposal. Work plans incorporating a proposal for a TSF should address aspects such as:

• The TSF design plan
• Details about the proposed management of the tailings and water
• Plans for the minimisation of impacts on native vegetation
• Plans for environmental monitoring and for managing rehabilitation, risks and emergencies
• Plans for the intended end-use of the TSF site.

A description of work plan requirements is provided in Appendix II.

The operator of a TSF may need to apply to the responsible authority (usually the local municipality) for planning approval under the Planning and Environment Act 1987.

Where a proposed TSF represents a minor variation to a pre-existing operation, the operator should confirm with the responsible authority whether further planning approval is required.

The operator must undertake consultation with the community and interested stakeholders in accordance with the site's community engagement plan.

This is particularly important where a proposed TSF represents a major change. Consultation enables the exchange of information, views about a project, the potential hazards and approaches to address them.

Consultation before and during the design and operation of the TSF should be part of the broader consultative process associated with the mining or extractive venture.

Site selection requires analysis of competing factors, such as the environment, local planning, social and cultural issues and landscape values that may be subject to regulation.

The operator proposing a TSF should identify and investigate all reasonable potential alternative sites and undertake realistic assessments of comparative risks.

A number of factors may influence selection related to the site itself, such as the:

• Downstream characteristics
• Flood or seismic activity
• Foundation conditions
• Availability of construction and rehabilitation materials
• Rehabilitation materials
• Depth to groundwater.

A catchment is a drainage basin (also known as a watershed). It describes a region of land where water from rain or snowmelt drains downhill into a body of water, such as a river, lake, estuary, wetland, sea or ocean or in this case, a tailings storage facility.

TSFs should be located and designed to have the smallest catchment possible. Matters that will be considered in assessing the TSF proposal include:

• The area and nature of the catchment
• Peak flows from storms and wet seasons
• The long-term stability of structures (such as stream diversions)
• Location of domestic water supplies
• Effects of drainage on downstream flow regimes (particularly flooding).

It is our policy that a proposal for a TSF with a significant external catchment will not be approved unless the operator can demonstrate that no better, practical alternative exists and that the environmental risks are adequately addressed.

Operators of such TSFs must meet the water management criteria described in the MTSF 2004 for large TSF, including capacity, freeboard and emergency spillways, in addition to the criteria described in these guidelines.

Water management is critical to the safety of a TSF.

Small TSFs without external catchment must:

• Be of sufficient size to contain waste inputs and rainwater during a one-in-ten year wet year
• Still retain a minimum one metre freeboard.

Alternatively, where an operator decides to undertake a detailed water balance that meets the water design criteria specified in MTSF 2004, a smaller freeboard may be approved.

Where diversion of clean runoff water around a TSF is required, works should be carefully designed to prevent downstream impacts such as erosion or siltation.

Design of diversion works should be based on site-specific hydrological data.

For small TSFs, appropriate design criteria for the safe and stable design of TSF and their embankments can be found in the guide to managing the safety of farm dams provided by the Department of Environment, Land, Water and Planning (DELWP).

This document is called Your dam: Your responsibility – A guide to managing the safety of small dams (PDF, 1.9MB).

Operators should demonstrate that the most appropriate method for managing the tailings has been selected.

Alternatives to wet storage systems are encouraged. This is particularly important if the nature of the tailings may compromise final rehabilitation of the TSF (such as slimes that will not dry successfully).

A small TSF usually involves constructing the embankment to its final height at the outset. Any future lifts must be specified (type and number) at the time of initial design.

TSFs must be designed to ensure that the potential use of groundwater and surface water are not compromised and to prevent undesirable impacts such as waterlogging and land salinisation.

The department may require more details of TSF construction in cases where these impacts are considered likely.

The department may also require a TSF to be lined in some circumstances.

The work plan should describe the method of closure and the source of the cover material.

TSFs require large quantities of cover material for closure and will benefit from a preliminary assessment of the geochemistry of tailings and identification of constituents with the potential to have an environmental impact.

The type and depth of cover are also influenced by the desired revegetation outcomes and future land use of the closed TSF.

All TSFs require an operations manual.

This provides the basis for ensuring that the work plan objectives are converted into appropriate on-site actions and that all personnel are informed of standard procedures, processes and performance measures that form part of their roles and responsibilities.

The size and complexity of the document will depend on the TSF and the site.

Aspects typically covered in an operations manual include:

• Roles and responsibilities by position
• Method for tailings conveyance and deposition
• Water management and maintenance of freeboard
• Inspection and maintenance schedules
• Dam safety and environmental monitoring
• Record keeping
• Reporting requirements
• Any additional requirements specified by the designer/department.

Personnel must have a detailed understanding of the operations manual's relevance to their day-to-day functions and responsibilities.

The operations manual must be continuously updated to reflect changes in site conditions or operations.

Tailings and decant waters are often pumped and conveyed by pipeline. This arrangement involves the risk of accidental discharge through a broken pipeline join or faulty control devices.

Measures to prevent accidental discharge of tailings must be in place. Procedures for pipeline inspections must be clearly outlined in the operations manual.

Other preventative measures to enable spillage to be directed to dedicated catch dams or to reduce the chance of liquid escaping under pressure include:

• Placing pipelines in trenches or between parallel bunds;
• Completely encasing the pipeline in a secondary sleeve or
• Constructing covers over pipe joints.

Appropriate maintenance and replacement schedules for mechanical equipment are necessary for safe operation.

Written records of inspection and maintenance of tailings pipelines and other tailings distribution equipment must be maintained and made available for review by the department upon request.

The operator should be able to demonstrate that the measures proposed and implemented reduce risks to an acceptable level.

Incidents, accidents and near misses associated with the management of tailings and tailings storage facilities must be reported to the department immediately or at the earliest practical time after control and mitigation.

Incidents related to a small TSF may include:

• Injury or death of personnel
• Injury or death of fauna on or near the TSF
• Uncontrolled release of tailings or supernatant water
• Major, unplanned, seepage impact on vegetation or groundwater accession
• Defects in the structure through cracking, slumping or erosion.

The consequences of a TSF failure may be serious. Part of the documentation required for approval of any TSF is an Emergency Response Plan (ERP).

The ERP should be prepared on the basis of a worst-case scenario relative to the size of the TSF and the nature of its contents.

A comprehensive discussion of this issue can be found in the DELWP publication Your dam: Your responsibility – A guide to managing the safety of small dams (PDF, 1.9MB) as well as the MTSF 2004.

Implementation of a plan could make a significant difference to the outcome of an incident. An Emergency Response Plan (ERP) should be prepared with scope and content related directly to the size and the identified hazards of the particular TSF, supporting the ERP for the overall mining or extractive operation.

The proforma TSF emergency response plan as set out in Appendix IV may be appropriate for many small TSFs.

The approved ERP should be kept in a prominent, accessible location known to all staff and emergency services. The ERP should also remain close to the operation centre of the mining or extractive operation for use in the case of an emergency.

A copy should be forwarded to each of the emergency services likely to attend the facility.

Monitoring and auditing are essential management tools for the operation of a TSF.

The work plan must include site-specific safety and environmental monitoring, auditing and reporting programs. The programs should be suitable for the nature and scale of the operation.

The operations manual should specify how the programs are to be implemented.

10.5.1 Safety monitoring

The aim of routine monitoring of a TSF is to provide early warning of danger so that timely maintenance can be carried out and failure avoided. Features to consider in a safety monitoring program may include:

Embankment

• Seepage, leakage, cracking, slips, movement or deformation
• Erosion
• Piezometric levels (knowing the phreatic surface location will assist).

Pond

• Level (minimum 1 metre freeboard)
• Location (pond against embankment may pose problems).

Structural

• Defects or obstruction in infrastructure (outlet pipes, spillway, decant system)
• Obstruction or erosion of diversion drains.

The guide Your dam: Your responsibility – A guide to managing the safety of small dams (PDF, 1.9MB) provides useful information on safety surveillance of small dams.

10.5.2 Environmental monitoring

Environmental monitoring requirements will depend on the type of tailings and risks involved.

For mining operations, this information should fulfil the reporting requirements of the Mineral Resources Development Regulations 2002 and of the work plan.

Environmental aspects to monitor may include:

• Impacts on surface and ground water
• Impacts on flora and fauna, including aquatic ecosystems
• Generation of dust, noise or odour
• Spray drift effects on adjacent vegetation (method impacts on dust/evaporation).

10.5.3 Monitoring of transfers for mining TSF

Monitoring of transfers to and from a mining TSF is required under Schedule 15 of the Mineral Resources Development Regulations 2002.

Further information on this is provided in MTSF 2004.

10.5.4 Auditing and reporting

Regular audits enable maintenance of and improvement to essential systems and procedures.

Audits also provide valuable comparisons of actual performance against the design parameters, expectations or assumptions in the work plan.

Records provide an ongoing history of the facility that is vital on sites with high personnel turnover. Any audit and review should be tailored to the size and nature of the TSF.

More information on audit and review reports for a TSF may be found in the MTSF 2004.

Early planning for closure can reduce risks to the environment and the operator, while minimising costs at the end of the project's life.

Most TSFs require large quantities of cover material and an operator must demonstrate a well planned closure, including sources for cover material in the initial work plan development.

While the diversity in materials and objectives make it impractical to prescribe designs for TSF covers, operators should demonstrate that a proposed cover is suitable for the nature of the contained tailings and the post mining or quarrying land use.

Proposed cover designs will be assessed as part of the work plan approval process.

The characteristics of the particular tailings and the topographic, hydrogeological, geotechnical and climatic characteristics of the disposal site usually determine the appropriate cover design.

Covers range from complex multilayers of earth and rock to those where only a relatively thin growing medium is required on the surface.

Designed for the long term, all TSF covers will require maintenance. TSFs on private land are normally subject to the requirements of the landowner agreement, which should take into account the long-term maintenance issues such as future land use and potential for erosion.

Monitoring of a decommissioned TSF should continue through formal closure and until resumption of management by the landowner. Post-closure monitoring may include:

• Revegetation performance
• Flood mitigation and drainage control
• Seepage
• Erosion control
• Control of pest plants and animals (include wild or plantation trees).

The monitoring must demonstrate that:

• Structures are geotechnically stable
• Covers are not eroding
• Risk of an uncontrolled release of tailings is very low
• Plant growth has been successful in meeting planned outcomes
• After several growing seasons, a self-sustaining vegetation community has developed.

Facilities on private land will normally be subject to the requirements of a landowner agreement. Landowners will need to account for the long-term maintenance costs when considering such agreements.

In addition, provisions of the MR(SD) Act make compensation payable to the Crown for losses associated with the use of Crown land for mining.

In either case, operators should make provision for the long-term costs associated with up-keep and maintenance.

Contaminated tailings –

1. tailings solids with contaminant concentrations (or predicted concentrations) above any of the levels specified in table 1, and/or sulphidic tailings with the potential to cause acid generation; and/or
2. tailings liquor (or predicted tailings liquor) with a total cyanide concentration exceeding 1 mg/l or a pH outside the range 5 to 9.

Tailings with these characteristics require higher standards of TSF design, construction and management.

Table 1: Maximum contaminant concentrations and elutriable fractions allowed in soil to be disposed of as contaminated soils (low level), based on EPA Victoria's classification of contaminated soils (EPA, 2004)

Note 1: Level of Mercury is based on the Victorian Department of Energy and Minerals Use of Mercury in the Gold Mining Industry (1994).

The following lists detailed information required by the department in relation to proposals for construction, operation and closure of small TSFs meeting the BLLC criteria outlined in section 3 this guideline.

These are additional to the basic requirements set out in the Mineral Resources Development Regulations 2002 or the Extractive Industry Development Regulations 1996.

Introduction

• Feneral description of method of raw material processing and tailings storage
• Brief summary of the proposal, including commencement and expected closure dates, the relationship with any existing (if relevant) or proposed operation
• Location map with AMG coordinates.

Environmental features of the site

• Geology of the area to be covered by the TSF (especially any features that might affect the water-tightness of the TSF)
• Topography of the site and immediate surrounding area, particularly to indicate the nature and extent of catchment and surface drainage pattern (the size of catchment should be the smallest practical)
• Details of any watercourses or water supply dams likely to be affected in the event of an accidental discharge from the site
• The potential for flooding
• Sources of materials for construction of the embankment, liners and closure (if the borrow pits are located outside the area subject to the mining licence, an extractive licence may be required under the Extractive Industry Development Act 1995)
• Location, extent and conservation status of any known potentially affected natural values (extant native vegetation, wetlands, groundwater, etc)
• Where removal of native vegetation is proposed an assessment in accordance with Victoria's Native Vegetation Management: A Framework for Action 2002
• Location or indications of any known rare or endangered flora or fauna at or near the site.

Cultural features of the site

• Location and nature of cultural features (Aboriginal, historic, recreational or landscape).

Tailings deposition methodology and waste minimisation

• Consideration of the principles of Waste Minimisation (Section 4)
• Source of the tailings including approximate process throughput rate (dry tonnes/year)
• Details of the chemical properties of the tailings, reagents, process and return waters and residual process chemicals.

Risk assessment

• Evaluation of the location of the TSF
• Identification of significant hazards to the environment, the community and infrastructure
• Identification of appropriate design features or actions required to eliminate or reduce risks to an acceptable level
• Identification of matters to be addressed in the emergency response plan.

TSF design

• Design parameters used (these may derive from approved small dam design manuals)
• Plan of the TSF site itself showing details and total area of structure, working area and ultimate tailings capacity (volume to include allowance for non-recovered water content)
• Erosion control measures for the embankment and toe.

TSF design for water management

• For TSFs with external catchments:
  • Determination of appropriate extreme rainfall events (see Section 9.1.1.1 and Appendix VII of MTSF 2004)
  • Analysis of the runoff into the TSF catchment for rainfall both on the storage itself and on the surrounding catchment (if applicable).
• Design, location and operation of discharge and return pipelines
• Design, location and materials of diversion drains.

Monitoring

• A program for monitoring, auditing and reporting safety, operational and environmental factors appropriate to the nature and scale of the operation as required by Section 17 of the guidelines.

Incident management

• Plans for recording and reporting all accidents, incidents and emergencies affecting health or safety of personnel, fauna, surface and ground water, vegetation, infrastructure (Section 10 of the guidelines).

Closure and rehabilitation

• Information on how closure is to be achieved in accordance with Section 10
• Details on erosion management
• Revegetation program.

Risk register (four sample entries)

The following procedures should be followed by the operator of a small tailings storage facility in the case of a major event or incident occurring at the facility.

Procedures for larger facilities could follow this format but should be more detailed.

Emergency events

• high rainfall
• storm
• earthquake

Emergency incidents

Overtopping, wave damage, cracking, slips, structural failure, slides, slumping, increased or new seepage, piping, pipeline leakage or other abnormal signs or behaviour.

Priority of action

1. saving life
2. protecting highly significant environmental values
3. saving property
4. dam structure damage control

Failure to apply due diligence under circumstances that could result in injury or damage to public or private property may constitute a liability against the TSF operator.

1. Be alert to potential developments and maintain close vigilance during extreme events or perceived abnormal behaviour of the TSF
2. Maintain safety requirements at all times during response actions
3. Take actions as outlined

Proforma small TSF ERP emergency response contacts

• Proforma small TSF ERP emergency response contacts (WORD - 14.1 KB)

Having made initial contact, the TSF operator shall make arrangements to maintain continuous contact and provide timely advice on changes of conditions.

Tailings storage facilities emergency processes

Structural failure

High rainfall or storm event

Earthquake event

Note: If the initial inspection was at night, follow-up inspections should be carried out in daylight.

Pipeline failure