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DEPARTMENT OF ENVIRONMENTAL QUALITY

 

DIVISION 43

CHEMICAL MINING

340-043-0000

Purpose and Policies

(1) The purpose of these rules and guidelines is to prevent water pollution and protect the quality of the environment and public health in Oregon, consistent with the policies of ORS 468B.015 and 468B.020, by requiring application of all available and reasonable method for control of wastes and chemicals relative to design, construction, operation, and closure of mining operations which use cyanide or other toxic chemicals to extract metals or metal-bearing minerals from the ore and which produce wastes or wastewaters containing toxic materials.

(2) The following policies are established to provide further guidance regarding the level of environmental protection these rules are intended to achieve:

(a) Liner, leak detection and leak collection systems (systems) are necessary for heap leach pads, solution ponds, and tailings facilities to assure that any leak will be detected before toxic materials escape from the liner system and are released to the environment. For purposes of these rules, the environment is considered to begin at the bottom of the last liner. These systems shall assure that a leak is found, and that sufficient time is available to allow for the repair of the leak and clean up of any leaked material before there is a release to the environment. Natural conditions, such as depth to groundwater or net rainfall, shall be considered as additional protection but not in lieu of the protection required by the engineered liner system;

(b) The toxicity of mill tailings and the potential for long-term cyanide and toxic metals release from mill tailings shall be reduced to the greatest degree practicable through removal, reuse, or destruction of chemical solutions prior to placement of tailings in the tailings disposal facility;

(c) The closure of heap leach pads and tailings disposal facilities shall prevent future release to the environment of residual potentially toxic chemicals contained in the facility.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468B.015, ORS 468B.020, ORS 468B.048 & ORS 468B.155
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0010

Definitions

Unless the context requires otherwise, as used in this Division:

(1) "Chemical Process Mine" means a mining and processing operation for metal-bearing ores that uses chemicals to dissolve metals from ores.

(2) "Department" means the Department of Environmental Quality.

(3) "Guidelines" means this body of rules contained in OAR 340-043-0080 through 340-043-0180.

(4) "Positive Exclusion of Wildlife" means the use of such devices as tanks, pipes, fences, netting, covers and heap-leach drip-irrigation emitters or covered emitters.

(5) "Tailings" means the spent ore resulting from the milling and chemical extraction process.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.030 & ORS 517.952
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0020

Permit Required

(1) As required by ORS 468B.050, a person proposing to construct a new chemical mining operation, commencing to operate an existing non-permitted operation, or proposing to substantially modify or expand an existing operation shall first apply for, and receive, a permit from the Department. The permit may be an NPDES (National Pollutant Discharge Elimination System) permit if there is a point-source discharge to surface waters or a WPCF (Water Pollution Control Facility) permit if there is no discharge. Consideration may be given to site-specific conditions such as climate, proximity to water, and type of wastes to establish the final permit type and requirements for the facility.

(2) The permit application shall comply with the require-ments of OAR Chapter 340, Divisions 14 and 45 and be accompanied by a report that fully addresses the requirements of this Division.

(3) Prior to issuance of a permit for a chemical process mining activity under this Division, a determination of compliance with statewide planning goals and compatibility with local land use plans must be made. The Department shall determine compliance with Statewide Planning Goals and compatibility with acknowledged comprehensive plans and land use regulations in a manner consistent with its approved State Agency Coordination Program and the rules in OAR Chapter 340, Division 18. In making these determinations, the Department shall consider and may rely on the findings and recommendations made by the project coordinating committee authorized by ORS 517.965 and by the Department of Geology and Mineral Industries pursuant to their State Agency Coordination Program and OAR Chapter 632, Divisions 1 and 37.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 197.180, ORS 468.065, ORS 468B.050 & ORS 517.965
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0025

Permit Conditions on Assumption of Liability

(1) This rule is necessary for the following reasons:

(a) ORS 468B.015 expresses an extremely strong state policy against pollution of the waters of the state; and

(b) ORS 468B.010 declares that the "water pollution laws of this state shall be liberally construed for the accomplishment of the purposes set forth in ORS 468B.015"; and

(c) ORS 468B.020 directs the Department to require the use of all available and reasonable methods necessary to achieve the purposes of ORS 468B.015; and

(d) Under ORS 468.065, the Department, in any permit it issues, is required to specify conditions for compliance with the rules and standards adopted by the Environmental Quality Commission pursuant to state law;

(e) Certain chemical process mines pose an unusual risk of substantial environmental harm;

(f) There is no significant operating history of chemical process mines in Oregon, and experience in other states demonstrates that, at least in some instances, chemical process mines have produced extraordinary environmental harm, and the permittees have escaped responsibility for such harm;

(g) It is inherent in the nature of chemical process mining that income from the mining activity will likely cease before the obligations and costs of the permittee, thereby creating a serious risk that pollution will not be abated unless adequate financial safeguards are required;

(h) The Reclamation Bond or alternative security required by ORS 517.987 and OAR 632-037-0135 for a chemical mining facility is intended to provide adequate resources to cover the costs of reclamation and a credible accident. The amount of security required is to be determined at the time permits are issued and adjusted as necessary during site operations. Lack of long-term experience with chemical mining activities makes it difficult to confidently estimate the full range of problems that could develop after chemical mining activities have ceased. This bond may not be adequate to address the full range of costs for protection and restoration of the environment if the permittee defaults;

(i) It is appropriate to take reasonable steps to assure continuing accountability from those who profit from chemical mining activities.

(2) Unless an exception is granted by the EQC pursuant to section (3) of this rule, and consistent with the provisions of section (4) of this rule, the Department shall require, prior to issuing or renewing a permit for a chemical mining facility, and as a condition of the permit, that those persons or entities who control the permittee assume liability for environmental injuries, remediation expenses, and penalties.

(3) The EQC may grant an exception to the requirements of section (2) of this rule upon entering a finding that a particular chemical process mine for which a permit is required does not pose a risk of substantial environmental harm. A finding under this section may be based upon one or more of the following factors which are deemed to relate to the risk of substantial environmental harm:

(a) Nature of the chemical mining process;

(b) Size and scope of the operations;

(c) Types of discharges;

(d) Sensitivity of the potentially affected environment;

(e) Difficulty and costs of implementing remediation measures;

(f) Potential for unintentional or unanticipated environmental injury and the potential magnitude of such injury; or

(g) Long-term operating history for the particular type of chemical process mine.

(4) If any of the securities of the permittee or of an entity assuming liability under section (2) of this rule are Publicly Traded, the investors of such Publicly Traded entity shall not be required to assume liability for environmental injuries, remediation expenses, and penalties. As used in this section, "Publicly Traded" means listed on the New York Stock Exchange or the American Stock Exchange or designated under the National Association of Securities Dealers Automated Quotations System, Inc., National Market System.

(5) As used in section (2) of this rule, "control" means the power to direct or exercise significant control over the management or policies of the permittee:

(a) The power to direct or exercise significant control arises principally from ownership, directly, indirectly or through intermediary entities, of the permittee;

(b) An important indicator of significant control arises from the ownership of or the power to vote ten percent (10%) or more of the securities of the permittee. Such ownership or voting rights may be either direct or indirect through intermediary entities;

(c) An important indicator that significant control exists arises if the entities share a significant number of common directors or officers;

(d) Individuals who hold status as officers, directors, employees, or agents of the permittee or intermediary entities shall not be deemed to fall under the definition of "control" for purposes of this rule solely as a result of such status;

(e) Commercial lending institutions operating within the scope of their normal business activities shall not be deemed to fall under the definition of "control" for purposes of this rule.

(6) The assumption of liability provided for in section (2) of this rule may, at the option of the persons or entities who control the permittee, be accomplished by joining with the permittee as a co-permittee or such other means as the Environmental Quality Commission, with advice of the Attorney General, may approve as being legally sufficient to protect the interests of the State of Oregon and its citizens.

(7) No permit for a chemical process mining activity shall be transferred without the prior written approval from the Department and full compliance with any applicable rules regarding permit transfer. Such approval may be granted by the Department when the transferee acquires a property interest in the permitted activity or agrees in writing to comply fully with all the terms and conditions of the permit and the applicable statutes and rules and demonstrates to DEQ's satisfaction the ability to fully comply.

(8) This rule shall apply to all permit applications either pending on or submitted after the effective date of this rule. This rule shall also apply to all transfers pending on or requested after the effective date of this rule and to all persons who control the associated transferee.

Stat. Auth.: ORS 468.020, ORS 468B.010, ORS 468B.015 & ORS 468B.020
Stats. Implemented: ORS 468.020, ORS 468B.010, ORS 468B.015, ORS 468B.020, ORS 468B.030 & ORS 517.956
Hist.: DEQ 9-1994, f. & cert. ef. 4-27-94

340-043-0030

Permit Application

(1) The permit application shall fully describe the existing site and environmental conditions, with an analysis of how the proposed operation will affect the site and its environment. The application shall, at a minimum, contain the information specified for the DOGAMI (Department of Geology and Mineral Industries) consolidated application under ORS 517.971 (Section 13, Chapter 735, 1991 Oregon Laws). The Department will also use the information contained in NEPA (National Environmental Policy Act), EA (Environmental Assessment), or EIS (Environ-mental Impact Statement) documents, if they are required for the project, as partial fulfillment of the requirements of this section.

(2) The permit application shall, in addition to the information described in section (1) of this rule, include the following information, unless the information has been otherwise submitted:

(a) Climate/meteorology characterization, with supporting data;

(b) Soils characterization, with supporting data;

(c) Surface water hydrology study, with supporting data;

(d) Characterization of surface water and groundwater quality;

(e) Inventory of surface water and groundwater beneficial uses;

(f) Hydrogeologic characterization of groundwater, with supporting data;

(g) Geologic engineering, hazards and geo-technical study, with supporting data;

(h) Characterization of mine materials and wastes which include, for example, overburden, waste rock, stockpiled ore, leached ore and tailings. Characterization of mine materials and wastes shall include, but not be limited to the following:

(A) Chemical and mineral analysis related to toxicity;

(B) Determination of the potential for acid water formation;

(C) Determination of the potential for long-term leaching of toxic materials from the wastes:

(i) Characterization of wastewater (quantity and chemical and physical quality) produced by the operation;

(j) Assessment of the potential for acid-water formation from waste disposal facilities, low-grade ore stockpiles, waste rock piles and for surface water or groundwater accumulation in open pits that will remain after mining is ended.

(3) Data submitted by the permit applicant should be based on analysis of the actual materials, when possible, or may be based on estimates from knowledge of similar operations and professional judgment.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 517.790, ORS 517.915, ORS 517.920 & ORS 517.971
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0040

Plan and Specifications

(1) A person constructing or commencing to operate a chemical process mine or substantially modifying or expanding an existing chemical process mine shall first submit plans and specifications to the Department for construction, operation and maintenance of the facilities intended for treatment, control and disposal of wastes.

(2) The plans shall address all applicable requirements of this Division and shall include, but not be limited to, the following:

(a) A description of the facilities to be constructed, including tanks, pipes and other storage and conveyance means for processing chemicals and solutions and wastewaters;

(b) A management plan for control of surface water;

(c) A management plan for treatment and disposal of excess wastewater, including provisions for reuse and wastewater minimization;

(d) A facility construction plan including, as applicable, the design of low-permeability soil barriers, the type of geosynthetics to be used and a description of their installation methods, the design of wastewater treatment facilities and processes, a quality assurance plan for applicable phases of construction and a listing of construction certification reports to be provided to the Department;

(e) A preliminary closure plan;

(f) A preliminary post-closure monitoring and maintenance plan;

(g) A spill containment and control plan.

(3) The Department shall approve the plans, in writing, before construction of the facilities may be started.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468B.055 & ORS 517.971
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0050

Design, Construction, Operation and Closure Requirements

(1) All chemical process and waste disposal facilities and facilities for mixing, distribution, and application of chemicals associated with on-site mining operations; ore preparation and beneficiation facilities; and processed ore disposal facilities shall be designed, constructed, operated and closed in accordance with the guidelines contained in this Division.

(2) Alternative facilities and methods of control of wastes and potential pollutants may be approved by the Department if the permit applicant can demonstrate that the alternate facilities and methods will provide environmental protection that is fully equivalent or better than that achieved by the facilities specified in the guidelines in OAR 340-043-0070 to 340-043-0180. The burden of proof of fully equivalent protection lies with the permit applicant. Written approval of any alternative by the Department shall be evidence of acceptance as equivalent or better level of environmental protection.

(3) A groundwater monitoring plan shall be submitted to, and be approved by the Department. Monitoring wells shall be installed for detection of groundwater contamination as required by OAR Chapter 340, Division 40, unless the Department concludes in writing that the hydrogeology of the site or other technical information indicates that an adverse impact on groundwater quality is not likely to occur.

(4) The Department may, in accordance with a written compliance schedule, grant reasonable time for existing facilities to comply with these rules.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468B.190, ORS 517.956 & ORS 517.971
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0060

Exemption from State Permit for Hazardous Waste Treatment or Disposal Facilities

(1) The state hazardous waste program requires a permit for the "treatment", "storage" or "disposal" of any "hazardous waste" as identified or listed in OAR Chapter 340, Division 101 from the Department, prior to the treatment and disposal of wastes. Permitting requirements can be found in OAR Chapter 340, Division 105, Hazardous Waste Management.

(2) However, any operation permitted under this Division, which would otherwise require the neutralization or treatment of hazardous waste and would require a permit pursuant to OAR Chapter 340, Division 105, shall be exempt from the requirement to obtain such hazardous waste treatment permit.

(3) All mined materials disposed of under this Division shall pass Oregon's hazardous waste rule criteria or they will be considered a state hazardous waste and must be disposed of accordingly.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 466.020 & ORS 468.020
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

Guidelines for the Design, Construction, Operation and

Closure of Chemical Mining Operations

 

340-043-0070

Purpose

(1) This Division establishes criteria for the design, construction, operation and closure of chemical mining operations and supplements the provisions of OAR 340-043-0000 through 340-043-0060. These criteria are intended to establish the minimum level of environmental protection that is necessary using a combination of performance standards and minimum design criteria. Approval of alternative facilities or methods to achieve an equivalent or better environmental result is allowed as defined in OAR 340-043-0050.

(2) Any disapproval of submitted plans or specifications, or imposition of requirements by the Department to improve existing facilities or their operation will be referenced when appropriate, to applicable guidelines or rules.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 468B.055
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0080

General Provisions

(1) Facilities permitted under either a WPCF or NPDES permit shall not discharge wastewater or process solutions to surface water, groundwater or soils, except as expressly allowed by the permit.

(2) Facilities subject to these rules shall not be sited in 100-year floodplains or wetlands. A buffer zone (a minimum of 200 feet wide) shall be established between waste disposal facilities and surface waters.

(3) All chemical conveyances (ditches, troughs, pipes, etc.) shall be equipped with secondary containment and leak detection means for preventing and detecting release of chemicals to surface water, groundwater or soils.

(4) Acid water accumulation in open pits resulting from the mining operation must be prevented by appropriate mining practices, by measures taken in the closure process, or be treated to control pH and toxicity, for the life of the pit.

(5) Construction of surface impoundment liner systems shall conform generally to the principles and practices described in EPA/600/2-88/052, Lining of Waste Containment and Other Impoundment Facilities, September 1988.

(6) The Department may require the permittee to hire a third-party contractor to perform the functions set forth below. Selection of the contractor shall be subject to Department approval:

(a) Review and evaluate the design and construction specifications of all mined-materials disposal facilities permitted under this Division for functional adequacy and conformance with Department requirements. The Department shall not approve construction of the disposal facilities until the design and construction specifications have been evaluated;

(b) Monitor the course of construction of all mined-materials facilities for compliance with the approved design and construction specifications. The third-party contractor shall regularly document the progress of construction and the Department shall require the permittee to take corrective action if construction does not satisfactorily conform to the approved design and construction specifications;

(c) Provide on-site inspections during ongoing operations, including but not limited to the loading of the heap, to assure protection of the integrity of the liner system and other environmental protection measures.

[Publications: The publication(s) referred to or incorporated by reference in this rule are available from the agency.]

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 468B.055
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0090

Control of Surface Water Run-On and Run-Off

(1) Surface water run-on and run-off shall be controlled such that it will not endanger the facility or become contaminated by contact with process materials or loaded with sediment. The control systems shall be designed to accommodate a 100-year, 24-hour storm event, or any other defined climatic event that is more appropriate to the site, and be placed so as to allow for restoration of the natural drainage network, to the maximum extent practicable, upon facility closure.

(2) All mined materials shall be properly placed and protected from surface water and precipitation so as not to be eroded and contribute sediment to site stormwater run-off or to otherwise contaminate surface water.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0100

Physical Stability of Retaining Structures and Emplaced Mine Materials

(1) Permit applicants must demonstrate to the Department that the design of chemical processing facilities and waste disposal facilities is adequate to ensure the stability of all structural components of the facilities during operation, closure and post closure.

(2) Retaining structures, foundations and mine materials emplacements shall be designed by a qualified, registered professional and be constructed for long-term stability under anticipated loading and seismic conditions.

(3) Temporary structures and materials emplacements may, with written approval from the Department, be constructed to a lesser standard if it can be shown that they pose no, or minimal, threat to public safety or the environment.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0110

Protection of Wildlife

(1) Wildlife shall be positively excluded from contact with chemical processing solutions and wastewaters containing chemicals.

(2) The Department may waive the positive exclusion requirement if the Oregon Department of Fish and Wildlife (ODF&W) certifies to the Department that the project is designed such that it will adequately protect wildlife.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 498.046
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0120

Guidelines for Design, Construction, and Operation of Heap-Leach Facilities

(1) This section applies to heap-leach facilities using dedicated, or expanding, pads. Heap-leach facilities using on-off, reusable pads may require variations from these rules; they shall be approved on a case-by-case basis by the Department.

(2) The heap-leach facility (pad and associated ponds, pipes and tanks) shall be sized to prevent flooding of any of its components.

(3) Table 1 of this Division establishes minimum capacity-sizing criteria for the leach-pad and ponds. The pad and ponds may be designed to act separately or in conjunction with each other to obtain the required storage volumes. Other design criteria may be used, with Department approval, if local conditions warrant. The best available climatic data shall be used to confirm the critical design storm event and estimate the liquid levels in the system over a full seasonal cycle. The liquid mass balance may include provision for evaporation.

(4) The heap leach pad liner system shall be designed, constructed, and operated to meet the following criteria:

(a) A primary liner consisting, at a minimum, of a continuous flexible-membrane of suitable synthetic material shall be provided. This liner shall function together with the process chemical collection system installed immediately above this liner (see section (8) of this rule) to remove process chemicals from the heap;

(b) A leak detection system shall be installed immediately below the primary liner for the purpose of detecting loss of process solutions by leakage through the primary liner. The leak detection system shall be capable of detecting leakage through the primary liner of 400 gallons/day-acre within ten weeks of leak initiation. The leak detection system shall consist of appropriately sized collection piping placed within a minimum thickness of 12 inches of permeable material (minimum permeability of 10-2 cm/sec) that is capable of withstanding the anticipated weight of the heap without loss of function;

(c) A secondary liner shall be placed below the leak detection system to provide assurance that any leakage through the primary liner during the operation of the heap and following closure of the heap is not released to the environment. The secondary liner shall be of a composite design with a continuous flexible-membrane of suitable synthetic material in direct contact with an engineered, stable, low permeability soil/clay bottom liner (maximum permeability of 10-7 cm/sec) with a minimum thickness of 36 inches;

(d) Each liner system component described in subsections (4)(a) - (c) of this rule addresses a specific need and purpose with respect to environmental protection. For purposes of evaluating alternative facilities and methods of control under OAR 340-043-0050(2), an alternative may be approved if the level of environmental protection intended by each separate liner system component is achieved either within the individual component or on a cross component basis.

(5) The processing chemical pond liner system shall be designed, constructed, and operated to meet the following criteria:

(a) A primary liner consisting, at a minimum, of a continuous flexible-membrane of suitable synthetic material shall be provided. This liner shall provide for positive containment of processing chemical solutions;

(b) A leak detection system shall be installed immediately below the primary liner for the purpose of detecting loss of process chemical solutions by leakage through the primary liner. The leak detection system shall be capable of detecting leakage through the primary liner of 400 gallons/day-acre within ten weeks of leak initiation. The leak detection system shall consist of appropriately sized collection piping placed within a layer of permeable material (minimum permeability of 10-2 cm/sec);

(c) A secondary liner shall be placed below the leak detection system to provide assurance that any leakage through the primary liner during the use of the pond is not released to the environment. The secondary liner shall be of a composite design with a continuous flexible-membrane of suitable synthetic material in direct contact with an engineered, stable, low permeability soil/clay bottom liner (maximum permeability of 10-7 cm/sec) with a minimum thickness of 36 inches;

(d) Each liner system component described in subsections (5)(a) - (c) of this rule addresses a specific need and purpose with respect to environmental protection. For purposes of evaluating alternative facilities and methods of control under OAR 340-043-0050(2), an alternative may be approved if the level of environmental protection intended by each separate liner system component is achieved either within the individual component or on a cross component basis.

(6) Emergency ponds may be constructed as an alternative to larger pregnant and barren ponds. The emergency pond may be constructed to a lesser standard, with the limitation that it is to be used only infrequently and for short periods of time. The Department will specify reporting and use limitations for the ponds in the permit. A between-liner leak detection system is not required for the emergency pond.

(7) The emergency pond liner shall be of composite construction consisting of:

(a) An engineered, stable, low permeability soil/clay bottom liner (maximum permeability of 10-6 cm/sec) with a minimum thickness of 12 inches; and

(b) A single flexible-membrane synthetic top liner of suitable material.

(8) The heap-leach pad shall be provided with a process chemical collection system above the upper-most liner that will prevent an accumulation of process chemical within the heap greater than 24 inches in depth.

(9) The permittee shall prepare a written operating plan for safe temporary shut-down of the heap-leach facility and train employees in its implementation.

(10) The permittee shall respond to leakage collected by the heap-leach and processing-chemical storage pond leak-collection systems according to the process defined in Table 2.

(11) The permittee shall determine the acid-generating potential of the spent ore by acid/base accounting and other appropriate static and dynamic laboratory tests. If the spent ore is shown to be potentially acid generating under the conditions expected in the heap at closure, the permittee shall submit a plan for acid correction for Department approval prior to loading the heap.

[ED. NOTE: The Table(s) referenced in this rule are not printed in the OAR Compilation. Copies are available from the agency.]

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 468B.160
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0130

Guidelines for Disposal of Mill Tailings

(1) Mill tailings shall be treated by cyanide removal, reuse, or destruction prior to disposal to reduce the amount of cyanide introduced into the tailings pond to the lowest practicable level. The permittee shall conduct laboratory column tests on mill tailings to determine the lowest practicable concentration to which the WAD cyanide (weak-acid dissociable cyanide as measured by ASTM Method D2036-82 C) can be reduced. In no event, shall the permitted WAD cyanide concentration in the liquid fraction of the tailings be greater than 30 ppm.

(2) The permittee shall determine the potential for acid-water formation from the tailings by means of acid-base accounting and other suitable laboratory static and dynamic tests. If acid formation can occur, basic materials shall be added to the tailings in the amount of three (3) times the acid formation potential or to give a net neutralization potential of at least 20 tons of CaCO3 per 1,000 tons of tailings, whichever is greater, before placing tailings in the disposal facility.

(3) The disposal facility shall be lined with a composite double liner consisting of a flexible-membrane synthetic top liner in tight contact with an engineered, stable, soil/clay bottom liner (maximum coefficient of permeability of 10-7 cm/sec) having a minimum thickness of 36 inches. Construction of the liner shall generally follow the principles and practices contained in EPA/600/2-88/052, "Lining of Waste Containment and Other Impoundment Facilities, September, 1988.

(4) The disposal facility shall be provided with a leachate collection system above the liner suitable for monitoring, collecting and treating potential acid drainage.

[Publications: The publication(s) referred to or incorporated by reference in this rule are available from the agency.]

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 468B.160
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0140

Guidelines for Disposal or Storage of Wasterock, Low-Grade Ore and Other Mined Materials

The permittee shall determine the acid-producing and metals-release potential of the wasterock, low-grade ore or other mined materials by acid/base accounting and other appropriate static and dynamic laboratory tests. If the mined materials are shown to be potentially acid forming, or capable of releasing toxic metals, the permittee shall submit a plan for correction and disposal for Department approval prior to permanently placing the materials.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

 

340-043-0150

Guidelines for Heap-Leach and Tailings Disposal Facility Closure

(1) The waste disposal facilities shall be closed under these rules in conjunction with the reclamation requirements of DOGAMI (Oregon Department of Geology and Mineral Industries).

(2) An updated closure plan and post-closure monitoring and maintenance plan shall be submitted to the Department by the permittee at least 180 days prior to beginning closure operations or making any substantial changes to the operation. The closure plan must be compatible with DOGAMI's reclamation plan and may be part of it.

(3) Chemical conveyances (ditches, troughs, pipes, etc.) not necessary for post-closure monitoring shall be removed. The secondary containment systems shall be checked before closure for process-chemical contamination, and contaminated soil or other materials, if any, shall be removed to an acceptable disposal facility.

(4) Closure of the heap-leach facility:

(a) The heap shall be detoxified over a suitable period of time prior to closure, using rinse/rest cycles of rinsing and chemical oxidation, if necessary. The WAD cyanide concentration in the rinsate shall be no greater than 0.2 ppm;

(b) Following detoxification as defined in subsection (a) of this section, the heap shall be closed in place on the pad by covering the heap with a cover designed to prevent water and air infiltration. The cover should consist, at a minimum, of a low-permeability layer and suitable drainage and soil layers to prevent erosion and damage by animals and to sustain vegetation growth, in accordance with DOGAMI's reclamation rules;

(c) The ponds associated with the heap shall be closed by folding in the synthetic liners and filling and contouring the pits with inert material. Residual sludge may be disposed of in one of the on-site waste disposal facilities, provided it meets the criteria for such wastes in these guidelines. The process chemical collection system of the heap shall be maintained in operative condition so that it can be used to monitor the amount and quality of infiltrated water, if any, draining from the heap.

(5) The tailings disposal facility shall be closed by covering with a composite cover designed to prevent water and air infiltration and be environmentally stable for an indefinite period of time. Maximum effort shall be made to isolate the tailings from the environment. Construction of the cover shall generally follow the principles and practices contained in EPA/530-SW-89-047. Technical Guidance Document -- Final Covers on Hazardous Waste Landfills and Surface Impoundments.

[Publications: The publication(s) referred to or incorporated by reference in this rule are available from the agency.]

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020 & ORS 517.770
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0160

Post-Closure Monitoring

(1) The Department may continue its permit in force for thirty (30) years after closure of the operation and will include permit requirements for periodic monitoring to determine if release of pollutants is occurring.

(2) Monitoring data will be reviewed regularly by the Department to determine the effectiveness of closure of the disposal facilities. The Department will consult with DOGAMI on release of security funds that would otherwise be needed to correct problems resulting from ineffective closure.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020, ORS 468B.050 & ORS 517.760
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0170

Land Disposal of Wastewater

(1) To qualify for land disposal of excess wastewater, the permit applicant shall demonstrate to the Department that the process has been designed to minimize the amount of excess wastewater that is produced, through use of water-efficient processes, wastewater treatment and reuse, and reduction by natural evaporation. Excess wastewater that must be released shall be treated and disposed of to land under the conditions specified in the permit.

(2) A disposal plan shall be submitted as part of the permit application that, at a minimum, includes:

(a) Wastewater quantity and quality characterization;

(b) Soils characterization and suitability analysis;

(c) Drainage and run-off characteristics of the site relative to land application of wastewater;

(d) Proximity of the disposal site to groundwater and surface water and potential impact;

(e) Wastewater application schedule and water balance;

(f) Disposal site assimilative capacity determination;

(g) Soils, surface water and groundwater monitoring plan;

(h) Potential impact on wildlife or sensitive plant species.

(3) The Department will evaluate the disposal plan and set site-specific permit conditions for the wastewater discharge.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020, ORS 468B.030 & ORS 468B.160
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

340-043-0180

Guidelines for Open-Pit Closure

(1) Open pits that will be left as a result of the mining operation shall be assessed prior to, and following, mining operations for the potential to contaminate water to the extent that it might not meet water-quality standards due to buildup of acid or toxic metals.

(2) If the Department finds that the potential for water accumulation in the pit(s) exists, the permit applicant shall submit a closure plan for the pit that will address contamination prevention and possible remedial treatment of the water. The closure plan shall, at a minimum, examine the following alternatives:

(a) Avoidance, during mining, of acid-generating materials that can be left in place, rather than being exposed to oxidation and weathering;

(b) Removal from the pit and disposal, during or after the mining operation, of residual acid-generating materials that would otherwise be left exposed to oxidation and weathering;

(c) Protective capping in-situ of residual acid-generating materials;

(d) Treatment methods for correcting acidity and toxicity of accumulated water;

(e) Installation of an impermeable liner under ponded water to prevent groundwater contamination;

(f) Backfilling of the pit(s) to the level necessary to, in conjunction with other appropriate control measures, prevent oxidation of residual acid-generating materials.

Stat. Auth.: ORS 468.020
Stats. Implemented: ORS 468.020, ORS 468B.030 & ORS 468B.160
Hist.: DEQ 23-1992, f. & cert. ef. 9-8-92

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