N.M. Admin. Code § 19.8.20.2034

Current through Register Vol. 36, No. 1, January 14, 2025

Section 19.8.20.2034 - DISPOSAL OF EXCESS SPOIL: GENERAL REQUIREMENTS

A. Spoil not required to achieve the approximate original contour within the area where overburden has been removed shall be hauled or conveyed to and placed in designated disposal areas within a permit area, if the disposal areas are authorized for such purposes in the approved permit application in accordance with 19.8.20.2034 through 2037 NMAC. The spoil shall be placed in a controlled manner to ensure:

(1) that leachate and surface runoff from the fill will not degrade surface or ground waters or exceed the effluent limitations of 19.8.20.2010 NMAC;

(2) stability of the fill; and

(3) that the land mass designated as the disposal area is suitable for reclamation and revegetation compatible with the natural surroundings.

B. The fill shall be designed using recognized professional standards, certified by a qualified registered professional engineer, and approved by the director.

C. All vegetative and organic materials shall be removed from the disposal area and the topsoil to be used as topdressing shall be removed, segregated, and stored or replaced under 19.8.20.2004 through 2008 NMAC. If approved by the director, organic materials may be used as mulch or may be included in the topdressing to control erosion, promote growth of vegetation, or increase the moisture retention of the soil.

D. Slope protection shall be provided to minimize surface erosion at the site. Diversion design shall conform with the requirements of 19.8.20.2011 NMAC. All disturbed areas, including diversion ditches that are not riprapped, shall be vegetated upon completion of construction.

E. The disposal areas shall be located on the most moderately sloping and naturally stable areas available as approved by the director. If such placement provides additional stability and prevents mass movement, fill materials suitable for disposal shall be placed upon or above a natural terrace, bench, or berm.

F. Excess spoil shall be transported and placed in a controlled manner in horizontal lifts not exceeding 4 feet in thickness; concurrently compacted as necessary to ensure mass stability and to prevent mass movement during and after construction; graded so that surface and subsurface drainage is compatible with the natural surroundings; and covered with topsoil or substitute material in accordance with 19.8.20.2007 NMAC. The director may approve a design which incorporates placement of excess spoil in horizontal lifts other than 4 feet in thickness when it is demonstrated by the operator and certified by a qualified registered professional engineer that the design will ensure the stability of the fill, will ensure a long-term static factor of 1.5, and will meet all other applicable requirements.

G. The final configuration of the fill must be suitable for postmining land uses approved in accordance with 19.8.20.2075 NMAC except that no depressions or impoundments shall be allowed on the completed fill unless approved by the director pursuant to Subsection C of 19.8.20.2055 NMAC.

H. Terraces may be utilized to control erosion and enhance stability if approved by the director and consistent with Subsection B of 19.8.20.2055 NMAC.

I. Where the pre-existing average slope in the disposal area exceeds 1v:2.8h (36 percent) or such lesser slope as may be designated by the director based on local conditions, the fill shall be designed and constructed using the services of a professional engineer who shall ensure stability of the fill and the foundation. Where the toe of the spoil rests on a downslope, stability analyses shall be performed in accordance with Subsection C of 19.8.9.909 NMAC to determine the size of rock toe buttresses and key-way cuts.

J. The fill shall be inspected for stability by a registered engineer or other qualified professional specialist experienced in the construction of earth and rockfill embankments at least quarterly throughout construction and during the following critical construction periods:

(1) removal of all organic material and top-soil to be used as topdressing;

(2) placement of underdrainage systems;

(3) installation of surface drainage systems;

(4) placement and compaction of fill materials; and

(5) revegetation.

K. The qualified registered professional engineer shall provide the director a certified report within 2 weeks after each inspection that the fill has been constructed and maintained as specified in the design approved by the director. The report shall include appearances of instability, structure weakness, and other hazardous condition. A copy of the report shall be retained at the mine site.

L. The certified report on the drainage system and protective filters shall include color photographs taken during and after construction, but before underdrains are covered with excess spoil. If the underdrain system is constructed in phases, each phase shall be certified separately.

(1) Where excess durable rock spoil is placed in single or multiple lifts such that the underdrain system is constructed simultaneously with excess spoil placement by the natural segregation of dumped materials, in accordance with 19.8.20.2037 NMAC, color photographs shall be taken of the underdrain as the underdrain system is being formed.

(2) The photographs accompanying each certified report shall be taken in adequate size and number with enough terrain or other physical features of the site shown to provide a relative scale to the photographs and to specifically and clearly identify the site.

M. Coal processing wastes shall not be disposed of in head-of-hollow or valley fills, and may only be disposed of in other excess spoil fills, if such waste is:

(1) placed in accordance with 19.8.20.2042 NMAC;

(2) demonstrated to be nontoxic and nonacid forming; and

(3) demonstrated to be consistent with the design stability of the fill.

N. If the disposal area contains springs, natural or manmade water-courses, or wet-weather seeps, an underdrain system consisting of durable rock shall be constructed from the wet areas in a manner that prevents infiltration of the water into the spoil material. The underdrain system shall be protected by an adequate filter and shall be designed and constructed using standard geotechnical engineering methods.

O. The foundation and abutments of the fill shall be stable under all conditions of construction and operation. Sufficient foundation investigation and laboratory testing of foundation materials shall be performed in order to determine the design requirements for stability of the foundation. Analyses of foundation conditions shall include the effect of underground mine workings, if any, upon the stability of the structure.

P. Excess spoil may be returned to underground mine workings, but only in accordance with a disposal program approved by the director and MSHA upon the basis of a plan submitted under 19.8.9.917 NMAC.

N.M. Admin. Code § 19.8.20.2034

11-29-97; 19.8.20.2034 NMAC - Rn, 19 NMAC 8.2.20.2034, 9-29-2000