Idaho Admin. Code r. 20.03.02.140

Current through September 2, 2024

Section 20.03.02.140 - BEST MANAGEMENT PRACTICES AND RECLAMATION FOR MINING OPERATION AND PERMANENT CLOSURE OF CYANIDATION FACILITIES

These are the minimum standards expected for all activities covered by these rules. Specific standards for individual mines may be appropriate based on site specific circumstances, and must be described in the plan.

01.Nonpoint Source Control.

a. Appropriate BMPs for nonpoint source controls will be designed, constructed, and maintained with respect to site-specific mining operations or permanent closure activities. Operators shall utilize BMPs designed to achieve state water quality standards and to protect existing beneficial uses of adjacent waters of the state. State water quality standards, as administered by DEQ, is the standard that must be achieved by BMPs.

b. If the BMPs utilized by the operator do not result in compliance with Subsection 140.01.a., the director shall require the operator to modify or improve such BMPs to meet the controlling, water quality standards as set forth in current laws, rules, and regulations.

02.Sediment Control. In addition to proper mining techniques and reclamation measures, the operator shall take necessary steps at the close of each operating season to assure that sediment movement associated with surface runoff over the area is minimized in order to achieve water quality standards, or to preserve the condition of water runoff from the mined area prior to commencement of the subject mining or exploration operations, whichever is the more appropriate standard. Sediment control measures refer to best management practices carried out within and, if necessary, adjacent to the disturbed area and consist of utilization of proper mining and reclamation measures, as well as specific necessary sediment control methods, separately or in combination. Specific sediment control methods may include, but are not limited to:

a. Keeping the disturbed area to a minimum at any given time through progressive reclamation;

b. Shaping waste to help reduce the rate and volume of water runoff by increasing infiltration;

c. Retaining sediment within the disturbed area;

d. Diverting surface runoff around the disturbed area;

e. Routing runoff through the disturbed area using protected channels or pipes so as not to increase sediment load;

f. Use of riprap, straw dikes, check dams, mulches, temporary vegetation, or other measures to reduce overland flow velocities, reduce runoff volume, or retain sediment; and

g. Use of adequate sediment ponds, with or without chemical treatment.

03.Clearing and Grubbing. Clearing and grubbing of land in preparation for mining exposes mineral soil to the erosive effects of moving water. Operators are cautioned to keep such areas as small as possible (preferably no more than one (1) year's mining activity) as the operator is required to meet the applicable surface water quality standards on all such areas. Where practicable, trees and slash should be stockpiled for use in seedbed protection and erosion control.

04.Overburden/Topsoil. To aid in the revegetation of affected lands where mining operations result in the removal of substantial amounts of overburden including any topsoil, the operator should remove the available topsoil or other growth medium as a separate operation for such area. Unless there are previously affected lands which are graded and immediately available for placement of the newly removed topsoil or other growth medium, the topsoil or other growth medium will be stockpiled and protected from erosion and contamination until such areas become available.

a. Overburden/Topsoil Removal.

i. Any overburden/topsoil to be removed should be removed prior to any other mining activity to prevent loss or contamination;

ii. Where overburden/topsoil removal exposes land area to potential erosion, the director, under the reclamation plan, may require BMPs necessary to prevent violation of water quality standards; and

iii. Where the operator can show that an overburden material other than topsoil is conducive to plant growth, or where overburden other than topsoil is the only material reasonably available, such overburden may be allowed as a substitute for or a supplement to the available topsoil.

b. Topsoil Storage. Topsoil stockpiles will be placed to minimize rehandling and exposure to excessive wind and water erosion. Topsoil stockpiles will be protected as necessary from erosion by use of temporary vegetation or by other methods which will control erosion, including, but not limited to, silt fences, chemical binders, seeding, and mulching.

c. Overburden Storage. Stockpiled ridges of overburden will be leveled in such a manner as to have a minimum width of ten (10) feet at the top. Peaks of overburden will be leveled in such a manner as to have a minimum width of fifteen (15) feet at the top. The overburden piles will be reasonably prepared to control erosion using best management practices; such activities may include terracing, silt fences, chemical binders, seeding, mulching or slope reduction.

d. Topsoil Placement. Abandoned affected lands must be covered with topsoil or other type of overburden that is conducive to plant growth, to the extent such materials are readily available, in order to achieve a stable uniform thickness. Excessive compaction of overburden and topsoil is to be avoided. Topsoil redistribution will be timed so that seeding, or other protective measures, can be readily applied to prevent compaction and erosion.

e. Fill. Backfill and fill materials should be compacted in a manner to ensure stability.

05.Roads.

a. Roads must be constructed to minimize soil erosion, which may require restrictions on the length and grade of the roadbed, surfacing of roads with durable non-toxic material, stabilization of cut and fill slopes, and other techniques designed to control erosion.

b. All access and haul roads must be adequately drained. Drainage structures may include, but are not limited to, properly installed ditches, water-bars, cross drains, culverts, and sediment traps.

c. Culverts that are to be maintained for more than one (1) year must be designed to pass peak flows from not less than a twenty (20) year, twenty-four (24) hour precipitation event and have a minimum diameter of eighteen (18) inches.

d. Roads and water control structures will be maintained at periodic intervals as needed. Water control structures serving to drain roads must not be blocked or restricted in any manner to impede drainage or significantly alter the intended purpose of the structure.

e. Roads that will not be recontoured to approximate original contours upon abandonment will be cross-ditched and revegetated, as necessary, to control erosion.

f. Roads that are not abandoned and continue to be used under the jurisdiction of a governmental or private landowner, will comply with the nonpoint source sediment control provisions of Subsection 140.02 until the successor assumes control.

06.Backfilling and Grading.

a. Every operator who conducts mining or cyanidation facility operations which disturb less than two (2) acres shall, where possible, contour the disturbed land to its approximate previous contour. These lands must be revegetated in accordance with Subsection 140.11.

b. An operator who conducts mining or cyanidation facility operations which disturb two (2) acres or more shall reduce all waste piles and depressions to the lowest practicable grade. This grade shall not exceed the angle of repose or maximum slope of natural stability for such waste or generate erosion in which sediment enters waters of the state.

c. Backfill and fill materials should be compacted in a manner to ensure mass and surface stability.

d. After the disturbed area has been graded, slopes will be measured for consistency with the approved reclamation plan or the permanent closure plan.

07.Disposal of Waste in Areas Other Than Mine Excavation. Waste material not used to backfill mined areas will be transported and placed in a manner designed to stabilize the waste piles and control erosion.

a. The available disposal area should be on a moderately sloped, naturally stable area. The site should be near the head of a drainage to reduce the area of watershed above the fill.

b. All surface water flows within the disposal area must be diverted and drained using accepted engineering practices such as a system of French drains, to keep water from entering the waste pile. These measures must be implemented in accordance with standards prescribed by the Idaho Stream Channel Protection Act, Title 42, Chapter 38, Idaho Code, and the Idaho Dam Safety Act, Sections 42-1710 through 42-1721, Idaho Code, if applicable.

c. The waste material not used in backfilling mined areas should be compacted, where practical, and should be covered and graded to allow surface drainage and ensure long-term stability.

d. The operator may, if appropriate, use terraces or slope reduction to stabilize the face of any fill. Slopes of the fill material should not exceed angle of repose or generate erosion in which sediment enters waters of the state.

e. Unless adequate drainage is provided through a fill area, all surface water above the fill must be diverted away from the fill area into protected channels, and drainage shall not be directed over the unprotected face of the fill.

f. The operator will conduct revegetation activities with respect to such waste piles in accordance with Subsection 140.11 of these rules.

08.Settling Ponds; Minimum Criteria.

a. Sediment Storage Volume. Settling ponds will provide adequate sediment storage capacity to achieve compliance with applicable water quality standards and protect existing beneficial uses, and may require periodic cleaning and proper disposal of sediment.

b. Water Detention Time. Settling ponds shall have an adequate theoretical detention time for water inflow and runoff entering the pond, but theoretical detention time may be reduced by improvements in pond design, chemical treatment, or other methods.

c. Emergency Spillway. In addition to the sediment storage volume and water detention time, settling ponds must be designed to withstand and release storm flows as required by the Idaho Dam Safety Act, Section 42-1710 through 42-1721, Idaho Code, and Safety of Dams Rules, where applicable.

09.Tailings Facilities. All tailings ponds, dams, or other types of tailings facilities must be designed, constructed, operated, and decommissioned so that upon their abandonment, the dam and impoundment area will meet applicable surface and ground water quality standards and not otherwise constitute a hazard to human or animal life.

a. Design criteria, construction techniques, and decommission techniques for tailings dams and impoundments shall comply with the Idaho Dam Safety Act, Sections 42-1710 through 42-1721, Idaho Code, and applicable rules and regulations.

b. Topsoil will be removed from the area to be affected by the impounding structure, tailings pond, or other tailings facilities in accordance with Subsection 140.04 of these rules.

c. Abandonment and Decommissioning of Tailings Impoundments.

i. Dewatering. Tailings ponds will be dewatered to the extent necessary to provide an adequate foundation for the approved post-mining use.

ii. Control of surface waters. Surface waters shall either be channeled around the reservoir and impoundment structure or through the reservoir and breached structure. Permanent civil structures must be designed and constructed to implement either method of channeling. The structure shall provide for erosion-free passage of waters and adequate energy dissipation prior to entry into the natural drainage below the impounding structure.

iii. Detoxification. Hazardous chemical residues within the tailings pond must be detoxified or covered with an adequate thickness of non-toxic material, to the extent necessary to achieve water quality standards in waters of the state.

iv. Reclamation. After implementing the required dewatering, detoxification, and surface drainage control measures, the reservoir and impounding structure will be covered with topsoil or other material conducive to plant growth, in accordance with Subsection 140.04 of these rules. Where such soils are limited in quantity or not available, and upon approval by the Department, physical or chemical methods for erosion control may be used. All such areas are to be revegetated in accordance with Subsection 140.11 of these rules, unless specified otherwise.

d. When the operator requests termination of its reclamation or permanent closure plan, pursuant to Section 150 of these rules, impoundment structures and any reservoirs retained as fresh water reservoirs after final reclamation or permanent closure are required to conform with the Idaho Dam Safety Act, Sections 42-1710 through 42-1721, Idaho Code, if applicable.

10.Permanent Cessation and Time Limits for Planting.

a. Seeding and planting of affected lands or a permanently closed cyanidation facility should be conducted during the first normal period for favorable planting conditions after final seedbed preparation.

b. Reclamation activities, where possible, are encouraged to be concurrent with the mining operation and may be included in the approved reclamation plan. Final reclamation must begin within one (1) year after the mining operations have permanently ceased on a mine panel. If the operator permanently ceases disposing of overburden on a waste area or permanently ceases removing minerals from a pit or permanently ceases using a road or other affected land, the reclamation activity on each given area must start within one (1) year of such cessation, despite the fact that all operations as to the mine panel, which included such pit, road, overburden pile, or other affected land, has not permanently ceased.

c. An operator is presumed to have permanently ceased mining operations on a given portion of affected land when no substantial amount of mineral or overburden material has been removed or overburden placed on an overburden dump, or no significant use has been made of a road during the prior three (3) years. If an operator does not plan to use an affected area for three (3) or more years but intends thereafter to use the affected area for mining operations and desires to defer final reclamation until after its subsequent use, the operator must submit a notice of intent and request for deferral of reclamation to the director, in writing. If the director determines that the operator plans to continue the operation within a reasonable period of time, the director shall notify the operator and may require actions to be taken to reduce degradation of surface resources until operations resume. If the director determines that use of the affected land for mining operations will not be continued within a reasonable period of time, the director may proceed as though the mining operation has been abandoned, but the operator will be notified of such decision at least thirty (30) days before taking any formal administrative action.

11.Revegetation Activities.

a. The operator shall select and establish plant species that can be expected to result in vegetation comparable to that growing on the affected lands or on a closed cyanidation facility prior to mining or cyanidation facility operations, respectively. Certified weed free seed should be used in revegetation. The operator may use available technical data and results of field tests for selecting seeding practices and soil amendments which will result in viable revegetation. These practices of selection may be included in an approved reclamation plan or permanent closure.

b. Unless otherwise specified in the approved reclamation or permanent closure plan, the success of revegetation efforts is measured against the existing vegetation on site prior to the mining or cyanidation facility operation, or against an adjacent reference area supporting similar types of vegetation.

i. The ground cover of living plants on the revegetated area should be comparable to the ground cover of living plants on the adjacent reference area for two (2) full growing seasons after cessation of soil amendment or irrigation.

ii. For purposes of this rule, ground cover is considered comparable if it has, on the area actually planted at least seventy percent (70%) of the premining ground cover for the mined area or adjacent reference area;

iii. For locations with an average annual precipitation of more than twenty-six (26) inches, the director, in approving a reclamation or permanent closure plan, may set a minimum standard for success of revegetation as follows: Vegetative cover of seventy percent (70%) for two (2) full growing seasons in areas planted to herbaceous species only; or fifty percent (50%) vegetative cover for two (2) full growing seasons and six hundred (600) woody plants per acre in areas planted to a mixture of herbaceous and woody species.

iv. As used in this section, "herbaceous species" means grasses, legumes, and other forbs; "woody plants" means woody shrubs, trees, and vines; and "ground cover" means the area of the ground surface covered by the combined aerial parts of vegetation and the litter that is produced naturally on-site, expressed as a percentage of the total area measured. Rock surface areas will be excluded from this calculation.

v. For previously mined areas that were not reclaimed to the standards required by Section 140, and which are affected by the mining or cyanidation facility operations, vegetation should be established to the extent necessary to control erosion, but shall not be less than that which existed before redisturbance; and

vi. Vegetative cover shall not be less than that required to control erosion.

c. Introduced species may be planted if they are known to be comparable to previous vegetation, or if known to be of equal or superior use for the approved post-mining use of the affected land, or, if necessary, to achieve a quick, temporary cover for soil stabilization purposes. Species classified as poisonous or noxious weed species shall not be used in revegetation.

d. By mutual agreement of the director, the landowner, and the operator, a site may be converted to a different, more desirable or more economically suitable habitat.

e. Planting of grasses and forbs should be done in a manner which promotes rapid stabilization of the soil surface. Wherever terrain permits, grasses and forbs should be drilled or compacted into the ground using agricultural grass planting equipment or other seeders specifically designed for mine revegetation applications. Broadcast and hydroseeding may be used on areas where other methods are impractical or unavailable.

f. The operator should plant shrubs or shrub seed, as required, where shrub communities existed prior to mining. Shrub seed may be planted as a portion of a grass seed mix or planted as bare-root transplants after grass seeding. Where the landowner desires a specific land use such as grazing or cropland, shrubs will not be required in the revegetation species mix. Shrub lands undergoing revegetation with shrubs will be protected from erosion by vegetation, chemical, or other acceptable means during establishment of the shrubs.

g. Reforestation. Tree stocking of forestlands should meet the following criteria:

i. Trees that are adapted to the site should be planted on the area to be revegetated in a density which can be expected over time to yield a timber stand comparable to premining timber stands;

ii. Trees will be established for two (2) full growing seasons after cessation of any soil amendments and irrigation before they are considered to be established; and

iii. Forestlands undergoing revegetation with trees should be protected from erosion by vegetation, chemical binders, or other acceptable means during seedling establishment.

h. Revegetation is not required on the following areas:

i. Affected lands, or portions thereof, where planting is not practicable or reasonable because the soil is composed of excessive amounts of sand, gravel, shale, stone, or other material to such an extent to prohibit plant growth;

ii. Any mined area or overburden stockpiles proposed to be used in the mining operations for haulage roads, so long as those roads are not abandoned;

iii. Any mined area or overburden stockpile, where lakes are formed by rainfall or drainage runoff from adjoining lands;

iv. Any mineral stockpile;

v. Any exploration trench which will become a part of a pit or an overburden disposal area; and

vi. Any road which is to be used in mining operations, so long as the road is not abandoned.

i. Mulching. Mulch should be used on severe sites and may be required by the reclamation or permanent closure plan where slopes are steeper than three to one (3:1) or the mean annual rainfall is less than twelve (12) inches. When used, straw or hay mulch should be obtained from certified weed free sources. "Mulch" means vegetation residues or other suitable materials to aid in the stabilization of soil and soil moisture conservation which will provide a micro-climate more suitable for germination and growth on severe sites. Annual grains such as rye, oats, and wheat may be used as a substitute for mulch where they will provide adequate protection and will be replaced by permanent species within a reasonable length of time.

12.Petroleum-Based Products and Chemicals. All refuse, chemical and petroleum products and equipment should be stored and maintained in a designated location away from surface water and disposed of in such a manner as to prevent their entry into a waterway.

Idaho Admin. Code r. 20.03.02.140

Effective March 18, 2022