Policy Guidelines and Standards for Mine Wastes and Mill Tailings Management

November 24, 1999

DENR MEMORANDUM ORDER NO. 32-99

 

Pursuant to Section 63 of Republic Act No.7942 otherwise known as the Philippine Mining Act of 1995, Section 166 (General Provision on Environmental Protection) of DENR Administrative Order No. 96-40, the Revised Implementing Rules and Regulations of RA 7942, Presidential Decree No. 984 of 1976, n the Pollution Control Law of the Philippines and Section 19, of Presidential Decree No. 1152 — the Philippine Environmental Code, these policy guidelines and standards with respect to mine wastes and mill tailings management in the Philippines are hereby promulgated. cdll

CHAPTER I

Introduction

SECTION 1. Title.

The title of this Memorandum Order shall be "Policy Guidelines and Standards for Mine Wastes and Mill Tailings Management".

SECTION 2. Scope.

These guidelines and standards shall govern all mine wastes and mill tailings management within the territory and exclusive economic zone of the Republic of the Philippines.

SECTION 3. Declaration of Policy.

It shall be the policy of the state that mine wastes and mill tailings produced by mining operators, permittees and contractors shall be managed in a technically, financially, socially, culturally and environmentally acceptable manner in a way that effectively safeguards the environment and protects the rights of concerned communities.

SECTION 4. Governing Principles.

Mine wastes and mill tailings shall be managed in adherence to the governing principle of sustainable development, which provides that its use shall be pro-environment and pro-people in sustaining wealth creation and improved quality of life under the following terms:

4.1 Management of mine wastes and mill tailings must be guided by current best practices committed to ensure control over its impacts and efficiently protect the environment; and

4.2 Mine wastes and mill tailings management shall be undertaken with due and equal emphasis on economic and environmental considerations, as well as safety, health, social and cultural concerns.

These principles are implemented through the specific provisions of this guidelines and standards for mine waste and mill tailings management.

SECTION 5. Objectives.

To effectively managed mine wastes and mill tailings in an environmentally sustainable manner as well as with an environmentally acceptable health, safety, social and cultural concern.

SECTION 6. Definition of Terms.

As used and for the purpose of these guidelines and standards, the following terms shall mean:

Angle of repose — the angle of steepest slope at which material will remain stable when loosely filed. The maximum angle that an unsupported mount of loose or broken materials will consistently form with the horizontal.

Camber — the crest settlement during construction and operation.

Crest of Dam — means the top of the dam generally sloped towards the reservoir to prevent water ponding.

Design Basis Earthquake (DBE) — the earthquake, which is liable to occur at least once during the expected life of the structure (also called operating basis earthquake, OBE).

Direct Shear Test — the method of determining the residual strengths of granular soils, e.g. sand, silt, gravel and of existing planes of weakness in the soil e.g. slide planes and fissures.

Deep Sea Tailing Placement — a technology whereby mill tailings are discharged through an engineered outfall at a location and depth selected to minimize environmental impacts.

Euphotic Zone — refers to the ocean's highest biological productivity zone where light allows photosynthesis and reproduction of marine plants to occur. The base of the euphotic zone is operationally defined as the depth reached by only 1% of light transmitted from the surface.

Flood Cycle — a period of time during which floods or sequence of floods occur.

Free Board — means the vertical distance between a specified reservoir water surface and the top of the dam without allowance for camber of the top of the dam.

'g' — the horizontal acceleration imparted by earthquakes, expressed in cm/second2, divided by the acceleration of gravity (9.81 cm/second2. The resulting ration is dimensionless called "k" or horizontal seismic coefficient.

Maximum Credible Earthquake (MCE) — the maximum earthquake event that can be conceived to affect the dam, taking into consideration the presence of potentially active faults in the vicinity of the dam.

Mill tailings — materials whether solid, liquid or both segregated from the ores during concentration/milling operations, which have no present economic value to the generator of the same.

Mill tailings placement facilities — refers to structures and equipment used in handling, transporting, disposing and/or impounding mill tailings.

Mine wastes — means solid and/or rock materials from the surface or underground mining operations with no present economic value to the generator of the same.

Mine Waste Dump — refers to a designated place where mine waste are accumulated or collected.

Mine Wastes Placement Facilities — refers to structures and equipment used in handling, transporting, disposing and/or impounding mine wastes.

Mixing Zone — the zone within which the concentrations of potential contaminants may exceed ambient water quality criteria. Compliance with ambient water quality criteria at the boundary of a site-specific mixing zone the dimension of which shall be established based on oceanographic and geochemical studies.

Operation Base Earthquake (OBE) — the earthquake which is liable to occur at least once during the expected life of the structure (also called Design Basis Earthquake, DBE).

Rock Mass Rating (RMR) — an empirical method developed to predict support requirements based from the sum of six properties: uniaxial compressive strength, Rock Quality Designation, joint spacing, quality of the joints, groundwater conditions, and joint orientation.

Rock Quality Designation (RQD) — a quantitative index based on core recovery procedure, which is determined by incorporation of only those pieces of core that are equal and/or more than 100 mm in length:

RQD	=	length of core in pieces ³ 100 mm
		—————————————
		Length of run

Only core of at least NX size (53 mm in diameter) should be used.

Secretary — means the Secretary of the Department of Environment and Natural Resources.

Static loading — a condition wherein the load applied to a body or mass is unidirectional and non-varying.

Surface mixed layer — the upper layer in the ocean, which is kept well mixed by the turbulent action of wind and waves. As a result, the surface layer tends to be of uniform temperature, salinity and density. The bottom of the surface mixed layer is generally marked by an abrupt density discontinuity which prevents tailings from rising upwards, providing the tailings is discharged below this density discontinuity. llcd

Unconfined/Uniaxial Compressive Strength (UCS) — the ability of a material to resist longitudinal stress without being confined at its sides.

Unified Soil Classification System (USCS) — a method most commonly used in classifying soil material on the basis of grain size usually by making the soil pass through a series of sieve.

CHAPTER II

Mine Wastes Storage

SECTION 7. Mine Wastes Storage Standards.

Mine wastes storage from mining operations creates a major visual and physical impact on the environment. Therefore, it is important to select, design, construct, operate, and rehabilitate/decommissioned mine waste storage sites such that they can be returned/converted to a productive long term and agreed land use.

SECTION 8. Guidelines on Site Selection of Mine Wastes Storage.

a. Mine waste storage shall be located far from old growth or virgin forest, proclaimed watershed forest reserves, wilderness areas, mangrove forests, mossy forests, national parks, greenbelts, game refuge, bird sanctuaries and areas proclaimed as marine reserves/marine parks, and tourist zones. As defined by law a buffer of not less than 500 meters from the perimeter shall be maintained;

b. Mine waste storage shall be located away from water bodies so that water flow after rehabilitation/decommissioning is reduced.

c. Mine waste storage close to coast shall be above the maximum storm surge level and a buffer of not less than 500 meters from the mean low tide level along the coast shall be maintained;

d. Mine waste storage shall take into consideration the expected life of the mine, the geology, hydrology, geochemistry, ecology, land use, topography, possible mineralization of the site area and climate.

e. Mine waste storage as much as possible shall accommodate mine waste produced from the entire life of mine operation;

f. Mine waste storage shall not be located on areas that might promote the generation of acid mine drainage (ARD);

g. Mine waste storage shall be designed and constructed above the maximum flood level;

h. In-pit dumping of mine waste shall be used/promoted whenever applicable. LexLib

SECTION 9. Guidelines to Design Mine Wastes Storage.

a. The expected life of the mine, the geology, local and regional seismicities, hydrology, geochemistry, ecology, land use, topography, climate, area of land available, vegetation of the site shall be considered in the design (e.g. height, slope, area, shape, etc.) of mine waste dumps.

b. Drainage system shall be constructed to handle heavy rainfall event. A 50-year flood (return period) shall be used for minimum design purposes.

c. Acid rock drainage (ARD) potential of mine wastes for impoundment shall be established. Mine waste characterized with ARD potential and/or classified as hazardous or with toxic leachates shall be contained separately from materials with no or lower potential ARD or non-toxic leachates. It shall be neutralized or treated by blending with waste materials of higher neutralizing potential or less hazardous materials/toxic leachates.

SECTION 10. Guidelines on the Construction of Mine Wastes Storage.

a. Site disturbance shall be limited and conform to the proposed design.

b. Drainage system shall be constructed during dump build-up and shall enable rainfall run-off to be shed from the dump without causing erosion.

c. Any pre-stripped vegetation matter shall be stockpiled separately;

d. The company must submit an "as-built-report" to the Bureau after completion of construction.

e. Stripped topsoil shall be contained and protected from erosion for future rehabilitation purposes.

f. Mine waste with potential ARD and hazardous leachates should be contain not to degrade the adjacent areas and the existing underground and surface waters.

SECTION 11. Guidelines on the Operation of Mine Wastes Storage.

a. Slopes of mine waste storage shall be maintained and managed below its angle of repose;

b. The different characteristics of mine waste shall be established. Those of the same characteristics shall be impounded separately with those of different characteristics in preparation for progressive/future rehabilitation.

c. Monitoring devices such as extensometers, movement hubs and survey stations shall be installed/provided during construction, active operation and even storage decommissioning;

d. Drainage system shall be provided to control siltation caused by surface-run-off;

e. Run-off from mine waste storage shall be collected/contained and monitored and shall be within the existing standards before allowing it to flow to existing tributaries or waterways.

f. Mine waste storage shall be protected from generating ARD and regularly monitored from generating such occurrences.

SECTION 12. Guidelines on Rehabilitation/Decommissioning of Mine Wastes Storage.

a. The final landform of mine waste storage shall be established in conformity with the existing surrounding environment or future land use and acceptable to the local community.

b. Where practicable, mine waste shall be returned to previously excavated areas;

c. All completed surfaces of waste dumps shall be stable and shall resist long term erosion;

d. Previously stockpiled subsoil and topsoil shall be spread on all completed surfaces where practicable and re-vegetated with suitable vegetation;

e. Slopes of decommissioned mine waste storage facilities shall be protected from progressive erosion by landscaping, planting of self-sustaining vegetation, or by means of a covering rock (rip-rapping);

f. Mine waste storage-covered areas shall be resolved, crop-covered or reforested if found unsuitable for more beneficial uses;

g. Surfaces of mine waste storage shall be rehabilitated and monitored prior to abandonment to a condition consistent with a sustainable productive use and/or acceptable to the existing community;

h. ARD generation shall be avoided or if not those storage generating ARD should be neutralized/treated before allowing to flow to existing water bodies.

CHAPTER III

Mill Tailings Storage

SECTION 13. On-land Mill Tailings Storage Standards.

On-land mill tailings storage of mining operations shall be located, designed, constructed, operated and rehabilitated/decommissioned such that they can be returned to productive long term and agreed land use;

SECTION 14. Guidelines on the Site Selection of On-land Mill Tailings Storage.

a. They shall be located far from declared watershed areas and free from spillage, slides, and/or washing away of tailings by surface runoff during heavy rains into adjacent areas and natural drainage systems (tributaries, creeks and/or rivers);

b. Impoundment in valleys (except cross-valley impoundment) shall be designed and constructed above the maximum flood level;

c. Placement of tailings solids into mined-out areas, whether on the surface or underground shall be carried out wherever this is both proven safe and practicable;

SECTION 15. Guidelines to Design Dam Embankment of On-land Mill Tailings Storage.

a. Impoundment close to the coast shall be above the maximum storm surge level;

b. Seismic consideration in the design of impoundment shall not be less than 0.15 and 0.25 g under Operation Base Earthquake (OBE) and Maximum Credible Earthquake (MCE) respectively;

c. Ground/impoundment foundation shall also be thoroughly analyzed to include drilling with Water Pressure Test (WPT), Rock Quality Designation (RQD), Unconfined/Uniaxial Compressive Strength (UCS), permeability (K), direct shear test, and Rock Mass Rating (RMR);

d. Impoundment formed of earth or earth and rock materials shall be designed and constructed with a factor of safety against failure of at least 1.2 under static loading conditions and at least 0.98 - 1.2 under maximum probable earthquake loading conditions;

e. Materials to be used for embankment shall also be analyzed as to its gradation, Atterberg limits, Unified Soil Classification System (USCS), consolidation, optimum moisture content, Unconfined/Uniaxial Compressive Strength (UCS) on remolded sample, direct shear test;

f. Embankments shall also be compacted to no less than ninety percent (90%) of proctor density;

g. Filter/drain zone shall always be provided along the entire length of the embankment. Provision of key (width = 0.25 H), buttress, grout curtain, apron, etc. shall always be implemented whenever necessary. llcd

SECTION 16. Guidelines on Dam Construction.

a. Freeboard requirement during dam construction stage shall take into consideration the hydrology/flooding in the area. Decant, and/or water diversion or spillway whenever necessary, shall also be provided.

b. A five (5)-year flood cycle shall be considered during dam construction stage.

c. Materials to be used for embankment shall be non acid and non toxic leachates generating materials.

d. The company shall submit an "as-built report" to the Bureau after the dam construction.

SECTION 17. Guidelines on the Operation of On-land Mill Tailings Storage.

a. Sufficient freeboard depending on the hydrological/flooding consideration shall likewise be maintained during operating life of the impoundment; A one hundred (100) year flood cycle shall be taken into account during active impoundment operation;

b. Embankment slopes shall be maintained below its angle of repose; a maximum angle of 1.1:1 along the upstream slope and 1.5:1 along the downstream slope;

c. Discharge of supernatant water from which tailings have settled will be permitted if it can be demonstrated that the dissolved constituents outside of a well-defined mixing zone, will conform to the existing and relevant Water Quality Criteria of the Department;

d. In cases where discharge does not meet the above standards but the receiving stream has a large capacity for dilution, a 'mixing zone' of no greater than 500-m long of the river shall be established. Within this zone, water quality is permitted to exceed the standards provided that activities within the zone will be controlled to ensure that the effects will be confined to the zone itself;

e. Monitoring devices to include piezometers, movement hubs and survey stations shall likewise be install/provided during construction, active operation and even impoundment abandonment;

f. Direct and indirect disposal of mill tailings and mine waste into natural drainage systems (including rivers and tributaries) are prohibited. Flushing of tailings is also prohibited;

g. Whenever practicable, all wastewater from tailings pond shall be recycled and utilized for mining and milling purposes. A zero wastewater discharged shall always be promoted.

SECTION 18. Guidelines on Rehabilitation/Decommissioning of On-land Mill Tailings Storage.

a. Sufficient freeboard, decant, water diversion or spillway shall be provided before decommissioning to ensure that it can withstand the maximum probable storm event without serious damage to the surrounding environment or to the tailings structure;

b. Outslopes of abandoned tailings storage shall be protected from progressive erosion by landscaping, the planting of self-sustaining vegetation, or by means of a covering rock (riprapping);

c. Tailings-covered areas shall be resolved, crop-covered or reforested if found unsuitable for more beneficial uses;

d. Surfaces of tailings storage shall be rehabilitated and monitored prior to abandonment to a condition consistent with a sustainable productive use and/or acceptable to the existing community;

e. Tailings storage shall avoid the generation of ARD. All generated acidic drainage's from tailings ponds shall be treated and neutralized before allowing to flow to the natural water systems.

SECTION 19. Conditions for the Use of Deep Sea Tailings Placement (DSTP).

Deep sea tailings placement systems shall be allowed only when other tailings disposal and management options are not environmentally, socially, technically and economically feasible or when deep sea tailings placement system exhibited the least environmental and social risk. Provided, further that there are significant constraints to on-land tailings storage such as but not limited to any of the following:

1. Lack of flat or gently sloping land for the construction of a safe, efficient and cost effective on-land tailing disposal system.

2. Heavy land use pressure (either existing or projected), particularly cultivated land or where slash and burn agriculture is used and the local community is dependent on subsistence gardening.

3. High seismic risk.

4. High rainfall, possibly including cyclones, and water surplus.

5. Poor geotechnical conditions for on-land storage structures.

The environmental and technical aspect of the system shall be in conformity with the acceptable international best practice. Further, tailings placement shall be within the carrying capacity of the receiving marine environment.

SECTION 20. Guidelines for the on Site Selection of Deep Sea Tailings Placement.

a. The site characteristics shall be such that the seafloor continues to slope towards an intended deep sea placement area, preferably a confined oceanic basin or trench.

b. Assessment of the selected site on its potential for oceanic upwelling so that there is minimal risk that tailings will be upwelled to the ocean surface. 

c. Assessment of existing and potential fisheries at the selected site and the predicted deep sea placement area. There shall be minimal conflict with fisheries during operations.

d. Political, regulatory and local community acceptance is essential if the underwater tailings placement option is to withstand NGO & media scrutiny.

SECTION 21. Guidelines for the Design of Deep Sea Tailings Placement.

a. The depth of the outfall shall be determined by in-situ measurements and modeling so that it will be located below the maximum predicted thickness of either the euphotic zone or surface mixed layer, whichever is deeper (normally > 100 m water depth).

b. The design shall ensure that the relative density of the tailing slurry is always greater than that of the influence of gravity and will form a bottom-attached and negatively-buoyant density current.

c. The tailings shall have low leachability of potential contaminants such as process reagents and metals both in the short term (in the water column prior to settling) and in the long term (on the ocean floor after settling).

d. After allowance for predischarge dilution and initial mixing with seawater in a 'mixing zone' beyond the outfall terminus, the concentrations of potential contaminants and the pore water within the deposited tailings shall be non toxic to marine life;

e. The dissolved constituents of the tailings beyond an immediate mixing zone shall conform to the existing and/or relevant Water Quality Criteria of the Department;

f. The accuracy of the environmental impact predictions shall be tested by undertaking validation studies and monitoring the actual effects of the underwater tailings placement system both throughout operations and post closure.

g. The density and flow conditions of the tailings stream at the outfall terminus shall be such that it promotes the creation of a coherent, bottom attached density current upon release. Preliminary fate of tailing modeling shall be undertaken to confirm that the tailings have every opportunity to settle in the intended placement area.

h. The system shall be designed to be flexible so that plant throughout can be expanded without the need for retrofit.

i. The tailings will settle in an area subject to high existing rates of sedimentation, whenever possible, the dissolved constituents of the tailings beyond an immediate mixing zone shall conform to the existing and/or relevant Water Quality Criteria of the Department;

j. A by-pass or stand-by system should be included in the design to manage tailings in case of pipeline failure or emergencies such as vandalism or earthquakes.

SECTION 22. Guidelines on the Preparation/Construction of Deep Sea Tailings Placement.

a. A detailed bathymetry survey and geotechnical assessment of potential subsea pipeline routes shall be undertaken to optimize route selection and avoid obstacles and areas of seafloor instability.

b. An assessment of nearshore wave conditions and littoral processes shall be undertaken such that designs can be prepared to protect the deaeration facilities and outfall pipeline in the nearshore area and in the surf zone.

c. Estimations of wave orbital velocities and ocean currents along the outfall pipeline route must be performed in order that the appropriate pipeline ballasting and other stabilization designs can be carried out.

SECTION 23. Guidelines on the Operation of Deep Sea Tailings Placement.

a. Adequate deaeration must be provided prior to discharge through the outfall pipeline.

b. The outfall pipeline shall be constructed from materials proven to be suitable for the marine environment and designs shall be sufficiently conservative to reflect the hostile environment in which the pipe will be placed into service.

c. Underwater tailings placement is not precluded in situations other than those described above. However, it is necessary to demonstrate clearly that:

1. Other disposal means are not feasible or underwater tailings placement will be less environmentally damaging than other alternatives;

2. Adequate compensation will be paid to any persons adversely affected by the actions; and

3. Overall benefits of the mining operation will more than offset the environmental losses that will be incurred as a result.

SECTION 24. Guidelines on Rehabilitation/Decommissioning of Deep Sea Tailings Placement.

a. All deep sea tailings placement facilities shall be dismantled;

b. The monitoring of the tailings placement area shall be incorporated in the Final Mine Rehabilitation/Mine Decommissioning Plan as per Section 187 of DAO 96-40;

c. Post discharge monitoring shall be undertaken to monitor both water quality and marine ecosystem recovery until such time that the metal constituents of the tailings have been established as non-toxic to marine life and the recovery of the marine populations to a level proximate the pre-discharge populations.

CHAPTER IV

Framework to Manage Mine Waste and Tailings Placement Facilities

SECTION 25. Guide to Manage Mine Wastes and Mill Tailings Storage/Placement Facilities.

To further enhance the implementation of Chapters III and IV of this Memorandum Order, the following framework to manage mine wastes and mill tailings facilities shall be strictly applied.

SECTION 26.  Framework to Manage Mine Waste and Mill Tailings Storage Placement Facilities.

A guiding principle of mine wastes and mill tailing management must be continual improvement in operational, safety and sustainable environmental performance, supported by periodical review and evaluation. The key elements of a framework to manage mine waste and mill tailings storage facilities, which is the foundation for the management action checklists stated in the attached annexes and which addresses wastes and tailings management through the full life cycle are as follows:

A. Policy and Commitment

Mining companies shall ensure that their policies include a commitment to:

1. Effectively safeguard the environment and protect the rights of existing communities;

2. Locate, design, construct, operate and close mine waste and mill tailings storage facilities in a manner such that:

2.1 All structures are stable and in compliance with company standards, government environmental policies and regulations, acceptable environmental practices, legislative requirements and commitments to stakeholders; and

2.2 All solids and water are managed within the designated areas intended in the design;

3. Take responsibility for implementing this framework through the commitments and actions of their employees; and

4. Establish an ongoing program of review and continual improvement to manage health, safety and environmental risks associated with mine waste and mill tailings storage facilities.

B. Planning

1. Roles and Responsibilities

The mine waste and mill tailings management team shall be established with clearly defined roles, responsibilities and authorities to implement the framework through all stages in the mine waste and mill tailings storage life cycle. llcd

2. Objectives

a. Mine waste and mill tailings storage shall be plan in accordance with this framework, company standards, legislative requirements, and sound engineering and sustainable environmental practices.

b. It shall be planned to identify and assess significant environmental and safety aspects, and their associated risks.

c. Prepare and document mine waste and mill tailings storage plans including descriptions of:

• aspects, objectives, targets and performance measures;

• permits and approvals;

• roles and responsibilities of key personnel;

• site selection and characterization criteria;

• safety, environmental and engineering design criteria;

• as built records;

• communication procedures with senior management and external stakeholders;

• construction, operation and rehabilitation/ decommissioning procedures and documentation requirements;

• monitoring, inspection, reporting and review requirements; and

• knowledge and skills (awareness, training and competence) requirements and training records.

d. Consult external stakeholders in the identification of appropriate community expectations for mine waste and mill tailings facilities.

e. Design the facilities for eventual closure to protect public health and safety, to mitigate negative environmental impacts and to meet acceptable post-closure use within a feasible technical and economic framework.

3. Managing Risk

Conduct risk assessment, including identification and evaluation of possible failure modes. Risk management shall be plan to:

a. Minimize the likelihood of adverse safety or environmental impacts;

b. Detect and respond to potential failures; and

c. Establish contingency and emergency preparedness plans to deal with significant events.

4. Managing Change

Prepare and document procedures to manage changes made to approve designs and plans during implementation. cdlex

5. Resources and Scheduling

Provide the essential resources and schedule for effective and efficient implementation of a mine waste and mill tailings management framework, including staffing, specialized skills development, technology and financial resources.

C. Plan Implementation

1. Operational Control

a. Select a site, design, construct, operate, decommission and close the storage facilities in accordance with the approved design, plans, sound engineering and sustainable environmental practices, and the management framework.

b. Identify, evaluate the impact of, and document changes made to approve designs and plans.

c. Acquire all required permits and approvals.

2. Financial Control

Implement a financial control system to track capital and operating costs toward meeting the objectives of the storage management.

3. Documentation

Prepare, maintain, periodically review and revise the required documents, including as-built drawings. Maintain current versions of all documents at identified locations. Promptly remove from uses obsolete versions of documents.

4. Competency

a. Employ qualified personnel for the storage design, construction, operation and closure. 

b. Provide appropriate training to all personnel, including contractors and suppliers, whose work may significantly affect the storage facility, on:

• facility management plans, permits and approval requirements;

• the importance of conformance to design;

• potential risks;

• significant actual and potential environmental impacts;

• emergency preparedness and response requirements; and

• their individual roles and responsibilities in achieving conformance with the requirements.

5. Monitoring

a. Put in place procedures to routinely inspect, monitor, test, record, evaluate and report on a regular basis key characteristics of the storage facility; include tracking of performance, operational controls and conformance with targets and objectives.

b. Calibrate equipment to ensure the reliability of data from monitoring and inspections.

6. Communications

Establish and maintain communication procedures for all personnel who have roles and responsibilities in implementing the placement management plan, including reporting of significant information and decisions to senior management and external stakeholders.

D. Audit and Mitigating Measures

1. Audit

a. In addition to routine monitoring and inspections, inspect and review on a periodic basis the entire storage facility to:

• examine facility implementation and conformance to plans and regulatory requirements;

• re-visit the facility design, construction, operation and closure plans and programs;

• re-evaluate downstream risks (which may change during the life of the facility);

• update consideration of possible failure modes, risk assessment and risk management; and

• identify items requiring corrective action.

b. Communicate promptly the results of inspections and review to senior management.

2. Mitigating Measure

a. Address items identified during inspections, reviews or audits that require mitigating measure.

b. Develop and implement action plans for these items, and record upon completion.

E. Management Review for Continual Improvement

1. Implement an annual senior management review of the adequacy of policies, objectives and performance of the management framework. Ensure that the scope of this review is appropriate to the level of identified risk.

2. Address the possible need for changes to policies, objectives and other elements in light of inspection reports, changing circumstances, recommendations and the commitment to continual improvement.

3. Encourage ongoing environmental and safety research to effect continual improvement.

SECTION 26. *  Framework Implementation.

To properly implement the above framework, the attached checklists as Annexes "A - D" and the attached applicable Technical considerations as references shall be applied in managing through the life cycle of mine waste and mill tailings storage facilities. prcd

CHAPTER VI

Implementation and Monitoring

SECTION 27. Clearance.

To fully implement compliance to this Memorandum Order, all mining applicants/permittees that will construct and/or operate mine wastes and mill tailings storage shall secure a clearance from the MGB or its Regional Offices without prejudice to applied permits from the concerned DENR agency/ies.

A Detailed guidelines regarding the implementation of this Section shall be formulated by MGB subject to the approval of the Secretary.

SECTION 28. Monitoring.

The MRF Committee through the Multi-Partite Monitoring Team shall include in its regular monitoring the compliance of the mining permittees to the guidelines. Permittees operating without the necessary clearance shall not be allowed to construct/operate the storage facilities. A report based on the monitoring shall be submitted to the CLRF - Steering Committee.

SECTION 29. Audit.

The report submitted by the MRF Committee shall be subject to annual audit by the CLRF-Steering Committee or its authorized representative.

That in case of DSTP, a Scientific and Technical Review Team independent from the CLRF, composed of government and university scientists and engineers with representatives from the company and the community, shall be constituted over the life of the mine to review all scientific and technical studies prepared for and by the company during any given year and may recommend additional studies to be undertaken when warranted.

SECTION 30. Non-issuance of Clearance.

The MGB or its Regional Offices may not issue the required clearance if based on their field evaluation/assessment and the documents submitted were not in accordance with this Memorandum Order. Permittees with pending/unsettled environmental requirements shall not be given any clearance unless all environmental commitments are cleared.

CHAPTER VII

Fees, Reporting Requirements and Penalties

SECTION 31. Mine Waste and Tailings Fees, Reporting Requirements and Penalties.

The provisions specified under DAO 96-40, Series of 1996, insofar as they are not inconsistent with the provisions of this Order, shall continue to govern tailings fees, reporting requirements and penalties.

SECTION 32. Tailings Fees for Deep Sea Tailings Placement.

The basic fee that shall accrue to the MWT Reserve Fund shall be PhP 0.10 MT of mill tailings.

SECTION 33. Penalty.

Tailings impoundment/disposal system found to have discharged and/or to be discharging solid fractions of tailings into areas other than the approved tailings storage area shall pay PhP 50.00/MT without prejudice to other penalties and liabilities the Contractor/Lessee/Permit Holder shall be subject under other existing laws, rules and regulations. Provided, that the said amount shall be deposited in a government depository bank to be used for payment for compensation for damages, rehabilitation, monitoring and decommissioning strategies of affected areas. LexLib

Withdrawal from the said fund shall be made by the Contractor/Permit Holder only with the written instruction to the bank issued by the MRF Committee authorizing the Contractor/Permit Holder to withdraw the said amount. The amount to be withdrawn shall be approved by the MRF Committee, copy furnished the CLRF Steering Committee.

SECTION 34. Additional Reporting Requirement for Deep Sea Tailings Placement System.

Contractor/Lessee/Permit Holder utilizing deep sea tailings placement upon issuance of the ECC, shall submit to the Bureau semi-annual report on the physical, chemical and biological features of the concerned marine environment. The MGB may also require other reports deemed necessary for the smooth implementation/operationalization of this Order.

CHAPTER VIII

Final Provisions

SECTION 35. Separability Clause.

If any action or provision of this Order is declared unconstitutional or invalid by a competent court, other sections or provisions hereof which are not affected thereby, shall continue to be in full force and effect, as if the sections or provisions so annulled had never been incorporated herein.

SECTION 36. Repealing Clause.

Any provisions of this Order and/or parts inconsistent thereof, inconsistent with law, other policy issuances and regulations, are hereby repealed and/or modified accordingly.

SECTION 37. Amendments.

This Order shall be accordingly amended and/or modified from time to time by the Department.

SECTION 38. Effectivity.

This Order shall take effect immediately after publication.

 

(SGD.) ANTONIO H. CERILLESSecretary

ANNEX A

 

CHECKLIST FOR SITE SELECTION AND DESIGN OF MINE WASTE AND MILL TAILINGS STORAGE FACILITY

 

ANNEX B

 

CHECKLIST FOR CONSTRUCTION OF MINE WASTE AND MILL TAILINGS STORAGE FACILITIES

 

ANNEX C

 

CHECKLIST FOR OPERATING MINE WASTE AND MILL TAILINGS STORAGE FACILITIES

 

ANNEX D

 

CHECKLIST FOR DECOMMISSIONING AND CLOSING MINE WASTE AND TAILINGS STORAGE FACILITY

 

ANNEX E

TECHNICAL CONSIDERATIONS

A. ENVIRONMENTAL BASELINE

The following is a summary of considerations for collecting and collating environmental baseline information for use in site selection, design and operation of mine waste and mill tailings facilities. This same baseline information is important for the development of closure plans and environmental monitoring programs. More comprehensive lists may be found in specific environmental assessment guidelines. prcd

1. EXISTING RESOURCES AND USE

Identify existing resources and land uses within the storage facility area and within the greater potential impact area.

Land and Water Use: Identify current and historical uses, including recreation, parks, aboriginal traditional use and land claims, human habitation, drinking water sources, archaeological considerations, mining, logging, farming, hunting and fishing.

Land Tenure: Establish the right to acquire the necessary land for a storage facility.

Identify land ownership and mineral rights, which may include mining claims; land-use permits; easements, including those for power lines and transportation corridors; Crown land; and aboriginal land claims.

2. BASELINE SCIENTIFIC DATA

Compile baseline environmental scientific data relevant to mine waste and mill tailings project area.

Physical

Climate - temperature, wind, precipitation, evaporation, return period floods, precipitation and runoff, air quality.

Water - hydrology, watershed delineation and flow patterns, stream flow, lake bathymetry, hydrogeology (groundwater) characteristics, surface water and sediment quality.

Land forms - including muskeg, peat or talus slopes.

Geology and geochemistry - surficial deposits (type, location, density, permeability), stratigraphy, geomorphology, mineral and petroleum resources, background elemental content.

Topography - regional and detailed topographic maps, stereo aerial photography, satellite imagery.

Soils - soils sampling and characterization. llcd

Natural hazards - landslides, avalanches, seismic events, flood potential, frost action.

Biological

Ecosystem identification.

Terrestrial survey - flora, natural pastures, fauna, endangered and threatened species, migratory species.

Aquatic survey - benthos, macro-invertebrates, fish, aquatic plants.

3. BASELINE SOCIO-ECONOMIC DATA

Compile baseline socio-economic data relevant to the tailings project area, including historical background, population, regional economy (e.g. health, education, culture, demography).

Identity socio-economic issues, which might arise for the tailings project.

B. MINE WASTE CHARACTERISTICS

Mine waste shall be characterized by its mineralogy; chemical properties; physical and engineering properties (e.g. strength, gradation, slaking potential); acid generating potential; teachable contaminants; ore grade and mine rock quantity and schedule. Also, the daily/annual throughput and total quantity; size distribution; % solids; density of solids; specific gravity; plasticity and liquid phase chemistry shall be determined.

C. MILL TAILINGS CHARACTERISTICS

The following examples of ore, mine rock (if used for dam construction or co-disposal) and tailings characterization information may be useful in design.

Ore and Mine Rock Characterization: Reserves; mineralogy; chemical properties; physical and engineering properties (e.g. strength, gradation, slaking potential); acid generating potential; leachable contaminants; ore, low-grade ore and mine rock quantity and schedule.

Tailings Characterization: Daily/annual throughput and total quantity; size distribution; % solids; density of solids; specific gravity; plasticity; liquid phase chemistry; acid generating potential. LexLib

Mill Operation Characteristics: Reagents used; water recirculation requirements; mill treatment processes (e.g. cyanide destruction); miscellaneous inflows to tailings basin; pipes and appurtenances; potential for pit and/or underground backfilling; % of disposal to surface facility vs. backfill.

D. MINE WASTE AND MILL TAILINGS STUDIES AND PLANS

The following is a summary of typical studies and plans which should be developed in the design of a tailings facility to an adequate level of detail relevant to each stage (conceptual, preliminary and detailed design) to enable approvals, then maintained throughout operation and closure:

• site selection documentation;

• emergency environmental assessment;

• risk assessment preparedness plan;

• deposition plan;

• water balance and management plan; and

• decommissioning and closure plan.

The plan contents listed are suggested minimums. There may be additional aspects, which should be included.

1. SITE SELECTION

Select a preferred site. Prepare a clearly documented rationale for selection, including discussion of alternate sites studied and rejected. Compile all relevant government legislation, regulation and guideline documents. Identify public perception issues related to the project (internal and external stakeholder requirements).

Environmental Considerations: Effluent treatment requirements; surface water contamination; groundwater contamination (hydrogeological containment); historical use of the receiving watershed; background environmental conditions; impact on vegetation, wildlife and aquatic life; natural flora and fauna; archaeological considerations; potential dust problems; aesthetic considerations; conceptual water balance.

Planning Considerations: Accessibility (road construction); distance from the mill; relative elevation from the mill; distance from habitation and areas of human activity; topography; existing land and resource use; property ownership and mineral rights; aboriginal land claims; transportation corridors, power lines, etc.; watershed and surface area considerations; volumetric capacity; dam volume/storage capacity ratio; geology, including potential ore bodies; construction material availability; conflict with mining activity; dam foundation conditions; basin foundation conditions; downstream hazards; hydrology; groundwater, contaminant seepage; potential impact area; human and environmental risk; water management scheme and preliminary water balance; operational plan; deposition plan; preliminary containment and water management structures; preliminary cost estimate based on preliminary considerations; conceptual risk assessment. prcd

Decommissioning/Reclamation Considerations: Flood routing requirements; revegetation potential; long-term stability; ease of establishing permanent drainage; reduction and/or control of acid drainage and other contaminants; dust control; long-term maintenance, monitoring and treatment requirements.

Development, Operating and Closure Cost Considerations: Capital cost; cost of tailings transport; tailings placement facility operating and maintenance costs; closure costs; cost per tonne of ore milled.

2. ENVIRONMENTAL ASSESSMENT

In order to obtain stakeholder and regulatory acceptance for siting a new storage facility, it is often necessary to conduct an environmental assessment, which can be a complex process involving federal and/or provincial regulators.

The environmental assessment process requires integration of knowledge about the project as it is being designed, the natural and social environments in which the project is situated, and community and stakeholder concerns.

At the environmental assessment stage, storage facilities are usually components of a larger, integrated project. The following is a summary of some significant aspects related to mine waste and mill tailings which should be addressed in an environmental assessment: environmental baseline; mine waste and mill tailings aspects; storage facility site selection, with a clearly documented rationale for the selected site; and conceptual storage facility design.

The environmental assessment should address the projected impacts of the storage facility on the environment, including physical impacts; physiography; climate; air quality; noise; hydrology; hydrogeology; water quality; biological impacts; aquatic life; vegetation; wildlife; archaeological impacts; socio-economic impacts; land-use impacts.

3. RISK ASSESSMENT

Risk assessment address what could go wrong (i.e. hazards or failure modes) with a facility and its associated plans and procedures; what are the probabilities of failure; and what are the consequences of failure. Risk assessment provides a basis for the development of risk management, including communication, contingency, mitigation and emergency response plans.

Risk should be assessed (and manage) through each phase of the life cycle of the storage facility. However, the intensity of assessment may vary at different stages, depending on the objectives of the review, complexity of the issue and the extent of information available.

Scope and Purpose of Assessment: Determine and document the scope and purpose of the risk assessment. Identify all stakeholders in the risk assessment.

Risk Assessment Team: An experienced, multi-disciplinary risk assessment team is required to determine potential failure modes, probabilities and consequences of failure.

The team might typically include the facility designer, construction contractor, operators, environmental and management staff and, in cases of detailed assessments, a risk assessment specialist. Consequence evaluation will involve environmental staff and specialists including, in some cases, health experts and cost engineers. Involving storage facility operating staff is critical for a risk assessment of an existing storage facility in order to incorporate their knowledge and experience of the facility.

Evaluation Criteria: Develop criteria to guide the evaluation of findings and establish levels of acceptable or unacceptable risk. High probability, high consequence failure modes would obviously be of concern, but low probability, high consequence modes may also require examination. Potential human health and safety, environmental impact or business (e.g. downtime, reputation, property damage) consequences should be considered.

Methodology: Risk assessment may be qualitative (subjective ratings of probability, consequence and overall risk) or quantitative (numeric values of probability and dollar values for consequences). A simple qualitative assessment may be appropriate to evaluate a number of potential storage sites whereas a detailed quantitative assessment would be more appropriate for a proposed major modification to an existing facilities.

Commonly practiced methodologies for risk assessment include process/system checklists; system design models; safety reviews; relative ranking; preliminary hazard analysis; "what-if" analysis; hazard and operability (HAZOP) studies; failure modes, effects (and criticality) analysis - FMEA, FMECA; probabilistic simulation analysis; fault-tree analysis; event-tree analysis; cause-consequence analysis; and human error analysis.

Potential triggers and failure modes: Reservoir overtopping - landslide into reservoir generates a wave which overtops the dam; wave action overtops dam; perimeter by-pass system fails and water enters reservoir, exceeding capacity of spillway or storage, or an external creek diversion failed and water entered reservoir; pond allowed to reach crest of dam; discharge from top end of pond to save dam height; blocked outlet structures; precipitation exceeds storage capacity; water balance not maintained.

Dam instability (upstream or downstream) - seepage causes piping and removes dam material (i.e. filter fails); seepage raises pore pressures and causes shallow instability; seepage raises pore pressures and causes deep instability; seismic liquefaction of dams; seismic deformation of dams; seismic liquefaction of tailings lead to erosion, seismic liquefaction of tailings applies horizontal thrust to dam; non-seismic liquefaction of dam to straining or increased pore pressures; seepage failure raises pore pressures and triggers a slide; construction pore pressures rise and slope moves; saturation of uncompacted fill either by first fill or rain or snow eucapsulated in dam fill melts, dam settles, overtops; uncontrolled toe erosion retrogresses; dam face erodes due to uncontrolled precipitation or snow melt.

Foundation instability - Karst collapses beneath dam; collapse due to mine subsidence allows tailings to escape into mine or void; sliding on weak soil or liner interface; compression of weak soils leads to cracking of dam; permafrost degrades; construction pore pressures rise and foundations move; seepage through a poor membrane or pervious soils into groundwater system, bypassing seepage recovery systems; seismic liquefaction of foundations; seismic deformation of foundations; non-seismic liquefaction of foundations.

Structural failures - piping around a culvert or decant pipe; reclaim tower fails; pumps fail due to loss of power; pipeline or conduit fails; landslide blocks spillway; ice blocks spillway.

Power failure

Probability of Failure: Estimate the probability of failure for each potential failure mode based on past experience with facility, experience with similar facilities, engineering analysis and professional judgment.

Consequences of Failure: Estimate consequences of failure for each potential failure mode, including consideration of impacts on health and safety of workers, contractors and general public; environmental impacts including consideration of assimilative capacity and environmental sensitivity of site; and business impacts.

Link to Operations: Identify operating, inspection and incident response (e.g. unusual occurrences) procedures which could reduce risk; and parameters and operating characteristics to be measured, monitored and documented to provide early warning of potential failure.

Reporting: Results of risk assessments should be clearly presented and summarized for both operating and management personnel. cdll

4. EMERGENCY PREPAREDNESS PLAN

It is of prime importance to be ready for emergencies and to have appropriate contingency and emergency preparedness plans in place. Emergency preparedness includes preparation both for on-site incidents and for incidents having off-site implications, including dam breach. Contingency and emergency preparedness plans should be reviewed on a periodic basis, tested, and widely distributed within an organization and to potentially affected external stakeholders. The site's emergency preparedness plan should integrate the storage facility aspects into the overall site emergency preparedness plan and should include, but not be limited to, the following:

• identification of planning coordinator, team and organization structure;

• identification of emergency organization, roles and responsibilities;

• identification of requirements of legislation, codes of practice, notification and reporting obligations;

• identification of available resources;

• mutual aid agreements;

• public relations plan;

• telephone lists;

• establishment of communication system for notifications and for post-notification purposes;

• risk analysis for on-site and off-site effects;

• inundation study, maps and tables for both physical and environmental releases (including dam break);

• basis for activation of emergency plan and emergency decision making;

• training of personnel;

• investigation and evaluation of incidents and accidents; and

• restoration of safe operating conditions.

5. MINE WASTE AND TAILINGS DEPOSITION PLAN

Waste and Tailings Deposition Plan: A waste and tailings basin deposition plan is developed for the expected mine life. Deposition plans can allow for the staging of dam lifts over the life of the mine to accommodate long-term storage of waste and tailings solids, maintain adequate solids storage capacity, and allow adequate polishing of supernatant during operation of the mine.

Incorporate appropriate consideration for expanded requirements and/or capacity.

Tailings deposition plan development requires tailings slurry quantity and density and production information estimated from the process/mill water balance, including provisions for estimating uncertainty and contingencies. The basic parameters should be validated and updated on a periodic or regular basis.

6. WATER BALANCE AND MANAGEMENT PLAN

Hydrology: Hydrology data, including the delineation of storage sites catchment area(s) and all potential water sources, both natural and process, are used in the development of a water/contaminant balance and design of storage facility components. Establish and document design parameters, then monitor actual experience to identify variances, validate projections and anticipate potential problems.

Design Flood: The appropriate Environmental Design Flood and Inflow Design Flood need to be identified, with reference to current design standards and in consultation with regulatory agencies. Design flood considerations should be consistently applied through all stages of the life cycle. Storage requirements, operating freeboard and spillway design are based on the hydrology of the watershed.

Water Balance: Complete a water balance study. Specify requirements for ongoing data collection for the mill and tailings basin water balance calibration purposes.

Surface Water Management Plan: Complete a water management plan detailing appropriate designs and strategies, where required, for seepage collection; reclaim/pump-back systems; treatment/discharge systems, including all water conveyance systems; and water retention and discharge strategy, including operating parameters.

Contaminant Balance and Release: The contaminant balance provides estimates of contaminant release to surface and groundwater. Develop, where required, a plan to control contaminant release within acceptable levels.

Effluent Criteria: Establish effluent criteria for the tailings placement facility, with reference to regulatory requirements and operating licenses and permits, including dissolved and suspended matter, including thiosalts; suspended solids; effluent quality; periods of discharge; bacterial and biological levels; and toxicity.

7. CLOSURE PLAN

Closure plans and performance criteria need to be developed in the early stages of facility design, and then verified and updated periodically through the operating life of the facility in preparation for decommissioning and closure. Closure is usually covered by regulations, and the following are general considerations applicable to development of closure plans. In some circumstances, closure may not be possible and decommissioning followed by long-term care may have to be done. This will require similar plans and controls as for closure.

Elements of a Closure Plan: Determine background data, including history of site, infrastructure, process flow controls, system operations, mineralogy, topography; hydrology/water management; hydrogeology; soil capability; revegetation; impact assessment, long-term maintenance; geotechnics; chemistry and geochemistry; monitoring program; communications; financial assurance; stakeholder consultation; potential end land use; and closure technology (i.e. dry cover, flooded, wetlands, perpetual treatment, vegetative cover).

Aspects of Dam Stability for Closure: Closure plans require a thorough re-assessment of storage facility and dam stability under closure conditions. All aspects of the facility and dam stability must be reviewed. In particular, the actual performance of the dams in service, including deformation, seepage, foundation and sidewalls, must be checked against design projections as well as against projected post-closure conditions. Design loads might be different after decommissioning and closure.

Structural monitoring and inspections should be continued for all storage facilities and dams until they are decommissioned and thereafter as appropriate. Identify and delineate any requirements for continuing inspection and/or monitoring of remaining structures after closure.

Prepare action plans to deal with shortcomings in closure quality and/or difficulties in complying with closure specifications.

Examine the consequences of closure of the facilities on emergency preparedness procedures, and update as appropriate. Ensure continuing availability of design, construction and operating records after closure for structures remaining in place.

E. DAM APPURTENANT STRUCTURES DESIGN

The following considerations relate to dam and containment basin design. The list may not apply to all sites or all situations. It is up to the design professional to decide which aspects apply. Site-specific conditions may require the use of additional criteria.

1. DESIGN INPUT CONSIDERATIONS

Compile information relating to the dam site from literature survey and field/laboratory investigation programs.

Hydrology and Hydrogeology: Hydrological and hydrogeology studies; water balance; water quality; design flood; freeboard requirements; drought design (i.e. water cover requirement); catchment runoff and diversion arrangements; deposition plan; erosion management plan.

Foundation, Geology and Geotechnical Engineering: Geomorphology; regional and local geology, faults; stratigraphy; bedrock and soil characteristics; geotechnical information, including compressibility, shear strength, angle of friction, grain size, density, plasticity, fractures, liquefaction potential, permeabilities, erosion potential, hydraulic fracture.

Construction Materials: Assess the availability of naturally occurring construction materials.

Assess the engineering characteristics of tailings and borrow materials, grout/concrete or other liner material (both natural and synthetic), such as grain size; density; volume; shear strength; permeability; acid generating potential; chemical reactivity (acid generating potential, reaction with pond water, thiosalt generating potential); wind and water erosion potential.

Determine potential detrimental effects of mine waste and mill tailings and/or process water on construction materials. Consider environmental impacts, stability and rehabilitation requirements for the use of any construction materials.

Topography: Regional and topographical mapping and air photos.

Special Environmental Considerations: Seismic risk; seismic attenuation of foundation strata and construction materials; liquefaction potential of foundation strata and construction materials; climatic conditions, including extreme values to be expected; wind and wave actions; permafrost effects; frost.

Seepage: Establish maximum allowable seepage objectives for environmental and structural requirements. Identify requirements for pervious vs impervious materials and construction methods. Develop a seepage management plan.

2. DESIGN ELEMENTS

Determine design parameters, including dam classification, stability, earthquake criteria, factors of safety, design permeabilities, acid rock drainage, wildlife, dust and closure considerations as outlined in the following sections.

Stability: Analyze the stability of the foundation, dam and appurtenances under conditions covering construction, operations and closure; and under static and dynamic conditions, including consideration of wave, frost/ice action and rapid drawdown.

Establish density and compaction targets.

Foundation Preparation: Determine the requirements for preparation of the dam and pond foundations prior to construction of the tailings dam and pond, including consideration of vegetation removal, including merchantable timber; excavation of organic soils; cut-off walls; groundwater control and containment; bedrock cleaning and slush grouting; high-pressure grouting; diversion wells; diversion channels; dewatering requirements; stability; constructability; other special construction requirements.

Seepage Analysis and Management: Assess the requirement for seepage control, including into groundwater, consideration of water chemistry and acid generating potential. Plan for implementation of appropriate measures, as warranted, such as filter design; cut-off wall; grout curtain; ditching; low permeability core; interception wells.

Appurtenances: Design, as required, for spillways; towers; pipelines (e.g. vacuum breakers, secondary containment); maximum flood-bandling requirements; gates and valves; siphons; pumps; natural hazards (e.g. debris, beavers, ice blockage).

Dam Design: Type of dam; design philosophy; criteria for major elements.

Dam Construction Plan: Develop a plan for executing the initial dam construction and subsequent dam lifts, including sequencing and requirements for stability monitoring.

Establish a construction methodology, schedule and anticipated costs. Determine potential environmental impacts due to construction of the proposed design.

Dam Monitoring Systems: Piezometers; inclinometers; settlement gauges; seepage flow monitoring; temperature (permafrost, frost penetration, heating).

Failure Mode Analysis: Analyze potential dam failure modes during construction, during operation, in its final condition and after closure.

Design for Closure: Coordinate designs elements with planning for eventual decommissioning and closure.

F. CONTROL AND MONITORING

Quality Assurance/Quality Control (QA/QC) Plan: Maintain construction drawings and as-built construction records throughout construction, operation and closure phases in an orderly and secure fashion, including revisions to construction drawings; test results; meeting minutes; construction photographs; monitoring notes.

Construction Control: Typical components of a construction management system include planning and scheduling; survey control (layout, as-built records); grouting monitoring; foundation preparation monitoring; material quality control; compaction control; instrumentation monitoring and data synthesis; record keeping; construction safety; construction environmental criteria.

Dust Control: Minimize dust releases from the tailings placement facility. This may include keeping the tailings wet and/or using short- or long-term chemical or organic covers.

1. Inspection of Mine Waste and Mill Tailings Dams

Performance monitoring - visual inspection - high frequency; groundwater pressure (pore water pressure); seepage; deformation (settlement and stability); weather influence; seismic events (after the fact); special inspection programs after major events (earthquakes, hurricanes, spring breakup, floods). LexLib

Indicators of instability - soft zones and boils along the toe; dirty sediment in seepage; increased seepage rates; new areas of seepage; longitudinal and transverse cracking; settlement.

Areas requiring special attention - spillways; decant structures; drain and pressure relief wells; concrete structures; pipes and conduits through dams; rip rap areas; siphons; weirs, trees and animal holes.

Stability Monitoring Program Plans: Location of control stations; schedule (control period and inspection); type of monitoring (visual inspections, measures and parameters); appropriate level of instrumentation (e.g. piezometers) with clearly identified purpose; inspection methods, data compilation and evaluation; persons responsible for monitoring; data storage and reporting systems; criteria to assess monitoring program.

2. Water Quality Plan

Hydrology - severe storm events and drought events; necessary information and parameters for water management activities; criteria to manage water levels within safe limits, including any required daily or seasonal water level control.

Water control - ensure that water can be safely managed within the confines of the system; prevent damage to all structures; review and revise as required after changes in design or methods, during and after construction program, when the pond level exceeds specified critical elevations, after major storm or spring melt events.

Perimeter dam seepage - evaluate potential for seepage from the tailings area; define levels and characteristics of acceptable seepage; prepare action plans to deal with deviations from design seepage. Performance measures include control of seepage to within design rates, and monitoring and controls to ensure that systems are performing as per design.

Tailings Deposition Plan: Ensure efficient use of the tailings capacity. Provide for long- and short-term scheduling of dam lifts. Ensure effective closure of the facility. Develop and validate against actual field conditions at pre-set intervals a schedule for deposition of the tailings and a filling curve (volume/elevation/graph). c

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n Note from the Publisher: Written as "Presidential Decree No. 3931 of 1976" in the original document.