Montana Code Annotated
Part 3. Metal Mine Reclamation
82-4-376. Tailings storage facility -- design document -- fee

82-4-376. Tailings storage facility -- design document -- fee. (1) An operator or a permit applicant proposing to construct a new tailings storage facility, an operator that is constructing a new tailings storage facility, or an operator proposing to expand an existing tailings storage facility shall submit to the department a design document and a $1,500 fee.
(2) The design document must contain:
(a) the certification of the engineer of record;
(b) a detailed description of the proposed facility and site characteristics;
(c) maps, sections, and appurtenances design drawings in both hard copy and electronic format with sufficient detail for an independent review;
(d) the raw data files for models used in developing and evaluating the design;
(e) an evaluation indicating that the proposed tailings storage facility will be designed, operated, monitored, and closed using the most applicable, appropriate, and current technologies and techniques practicable given site-specific conditions and concerns;
(f) a site geotechnical investigation commensurate in detail and scope with the complexity of the site geology and proposed tailings storage facility design. The investigation must include a geological model of site conditions and a rationalization of the site investigation process.
(g) a demonstration through site investigation, laboratory testing, geotechnical analyses, and other appropriate means that the tailings, embankment, and foundation materials controlling slope stability are not susceptible to liquefaction or to significant strain-weakening under the anticipated static or cyclic loading conditions, to the extent that the amount of estimated deformation under the loading conditions would result in loss of containment;
(h) for a new tailings storage facility, design factors of safety against slope instability not less than:
(i) 1.5 for static loading under normal operating conditions, with appropriate use of undrained shear strength analysis for saturated, contractive materials;
(ii) 1.3 for static loading under construction conditions if the independent review panel created pursuant to 82-4-377 agrees that site-specific conditions justify the reduced factor of safety and that the extent and duration of the reduced factor of safety are acceptable; and
(iii) 1.2 for postearthquake, static loading conditions with appropriate use of undrained analysis and selection of shear strength parameters. Under these conditions, a postearthquake factor of safety less than 1.2 but greater than 1.0 may be accepted if the amount of estimated deformation does not result in loss of containment.
(i) for a new tailings storage facility, an analysis showing that the seismic response of the tailings storage facility does not result in the uncontrolled release of impounded materials or other undesirable consequences when subject to the ground motion associated with the 1-in-10,000-year event, or the maximum credible earthquake, whichever is larger. Any numeric analysis of the seismic response must be calculated for the normal maximum loading condition with steady-state seepage. The analysis must include, without limitation, consideration of:
(i) anticipated ground motion frequency content;
(ii) fundamental period and dynamic response;
(iii) potential liquefaction;
(iv) loss of material strength;
(v) settlement;
(vi) ground displacement;
(vii) deformation; and
(viii) the potential for secondary failure modes.
(j) if a pseudo-static stability analysis is performed to support the design, a justification for the use of the method with respect to the anticipated response to cyclic loading of the tailings facility structure and constituent materials. The calculations must be accompanied by a description of the assumptions used in deriving the seismic coefficient.
(k) reduced factors of safety or seismic design criteria if the independent review panel agrees that site-specific conditions justify that design to the specified requirements of factors of safety or seismic design criteria in this section is not necessary;
(l) for expansion of an existing tailings storage facility, either an analysis showing the proposed expansion meets the minimum design requirements for a new tailings storage facility under this section or an analysis showing the proposed expansion does not reduce the tailings storage facility's original design factors of safety and seismic event design criteria;
(m) a probabilistic and deterministic seismic evaluation for the area and assessment of peak horizontal ground acceleration;
(n) a dam breach analysis, a failure modes and effects analysis or other appropriate detailed risk assessment, and an observational method plan addressing residual risk;
(o) a description of the chemical and physical properties of the materials and process solutions to be stored in the tailings storage facility;
(p) when appropriate, depending on the chemical and physical properties of the materials, a detailed description of how undesirable constituents contained in the impoundment will be isolated from the environment;
(q) a description of the tailings storage facility capacity over time and the estimated ultimate capacity;
(r) specifications for impoundment construction, including the specifications for the foundation, abutments, embankment, means of containment, and the borrow materials;
(s) a construction management plan that includes, at a minimum, parameters and levels of acceptability to be monitored during construction for quality control and quality assurance purposes. The frequency of sampling, the amount of oversight, the qualifications of the oversight personnel, and the role of the panel during and after construction must be specified and agreed to by the panel.
(t) a list of quantitative performance parameters for construction, operation, and closure of the tailings storage facility. The quantitative performance parameters may be expressed as minimums or maximums for embankment crest width, embankment slopes, beach width, operating pool volume, phreatic surface elevation in the embankment and foundation, pore pressures, or other parameters appropriate for the facility and location.
(u) a list of the assumptions used during the analysis and design of the facility and a description justifying the validity of each assumption;
(v) a description of how the design integrates into a closure plan that facilitates, to the extent possible, dam decommissioning resulting in a maintenance-free closure;
(w) requirements for postclosure monitoring, inspection, and review, including the frequency of engineer of record inspections, independent panel reviews, and retention of an engineer of record;
(x) a description of proposed risk management measures for each facility life-cycle stage, including construction, operation, and closure;
(y) a detailed water balance, evidence of calibration if available, and the raw data used to develop the water balance;
(z) a detailed description of how water, seepage, and process solutions are to be routed or managed during construction, operation, and closure;
(aa) a detailed description of storm water controls, including diversions, storage, freeboard, and how extreme storm events will be managed;
(bb) a design storm event for operation and closure conforming to current engineering best practices for the type of facility proposed that includes:
(i) a rationale for the selection of the design storm event;
(ii) the magnitude of the design storm event;
(iii) the magnitude of runoff generated by the design storm event to and around the impoundment; and
(iv) evidence that the dynamic nature of climatology was considered;
(cc) for a new tailings storage facility, design sufficient to store:
(i) the probable maximum flood event plus maximum operating water or solution volume plus sufficient freeboard for wave action; or
(ii) a flood event design criterion less than the probable maximum flood but greater than the 1-in-500-year, 24-hour event if the panel agrees that site-specific conditions justify that design to the probable maximum flood standard is unnecessary;
(dd) for an expansion of an existing tailings storage facility, either an analysis that the proposed expansion meets the minimum requirements in this section to manage storm or flood events or an analysis that the expansion does not reduce the tailings storage facility's ability to store or otherwise manage the original facility design storm or flood events; and
(ee) any other information, drawings, maps, detailed descriptions, or data to assist the panel in determining if the new or expanded tailings storage facility protects human health and the environment.
(3) The design document must be submitted prior to the issuance of the draft permit pursuant to 82-4-337.
History: En. Sec. 5, Ch. 399, L. 2015.

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