New Mexico Administrative Code
Title 19 - NATURAL RESOURCES AND WILDLIFE
Chapter 8 - COAL MINING
Part 20 - PERFORMANCE STANDARDS - SURFACE COAL MINING OPERATIONS
Section 19.8.20.2037 - DISPOSAL OF EXCESS SPOIL: DURABLE ROCK FILLS

Universal Citation: 19 NM Admin Code 19.8.20.2037

Current through Register Vol. 35, No. 18, September 24, 2024

In lieu of the requirements of 19.8.20.2035 and 2036 NMAC, the director may approve alternate methods of disposal of hard rock spoil, including fill placement by dumping in a single lift, on a site specific basis, provided the services of a registered professional engineer experienced in the design and construction of earth and rockfill embankments are utilized and provided the requirements of 19.8.20 NMAC and 19.8.20.2034 NMAC are met. For 19.8.20 NMAC, hard rock spoil shall be defined as rockfill consisting of at least 80 percent by volume of sandstone, limestone, or other rocks that do not slake in water. Resistance of the hard rock spoil to slaking shall be determined by using a slake index and slake durability tests approved by the director.

A. Spoil is to be transported and placed in a specified and controlled manner, which will ensure stability of the fill.

(1) The method of spoil placement shall be designed to ensure mass stability and prevent mass movement in accordance with the additional requirements of 19.8.20 NMAC.

(2) Loads of noncemented clay shale and/or clay spoil in the fill shall be mixed with hard rock spoil in a controlled manner to limit on a unit basis concentrations of noncemented clay shale and clay in the fill. Such materials shall comprise no more than 20 percent of the fill volume as determined by tests performed by a registered professional engineer and approved by the director.

B. Stability analyses.

(1) Stability analyses shall be made by the registered professional engineer. Parameters used in the stability analyses shall be based on adequate field reconnaissance, subsurface investigations, including borings and laboratory tests.

(2) The embankment which constitutes the valley fill or head-of-hollow fill shall be designed with the following factors of safety.

Case Design Condition Minimum Factor of Safety

I End of construction 1.5

II Earthquake 1.1

C. The design of a head-of-hollow fill shall include an internal drainage system to the extent necessary to ensure continued free drainage of anticipated seepage from precipitation and from springs or wet weather seeps.

(1) Anticipated discharge from springs and seeps and due to precipitation shall be based on records and/or field investigations to determine seasonal variation. The design of the internal drainage system shall be based on the maximum anticipated discharge.

(2) All granular material used for the drainage system shall be free of clay and consist of durable particles such as natural sands and gravel, sandstone, limestone of other durable rock which will not slake in water.

(3) The internal drain shall be protected by a properly designed filter system.

D. Surface water runoff from the areas adjacent to and above the fill shall not be allowed to flow onto the fill and shall be diverted into stabilized channels which are designed to pass safely the runoff from a 100-year, 24-hour precipitation event. Diversion design shall comply with the requirements of Subsection F of 19.8.20.2011 NMAC.

E. The top surface of the completed fill shall be graded such that the final slope after settlement will be no steeper than 1v:20h (5 percent) toward properly designed drainage channels in natural ground along the periphery of the fill. Surface runoff from the top surface of the fill shall not be allowed to flow over the outslope of the fill.

F. Surface runoff from the outslope of the fill shall be diverted off the fill to properly designed channels which will pass safely a 100-year, 24-hour precipitation event. Diversion design shall comply with the requirements of Subsection F of 19.8.20.2011 NMAC.

G. Terraces or other suitable controls, such as berms, contour furrows, or micro-depressions, shall be constructed on the outslope if required for control of erosion, or terraces for construction of roads included in the approved postmining land use plan. Terraces shall meet the following requirements:

(1) the slope of the outslope between terrace benches shall not exceed 1v:2h (50 percent);

(2) to control surface runoff, each terrace bench shall be graded to a slope of 1v:20h (5 percent) toward the embankment; runoff shall be collected by a ditch along the intersection of each terrace bench and the outslope;

(3) terrace ditches shall have a 5 percent slope toward the channels specified in Subsection F of 19.8.20.2037 NMAC, unless steeper slopes are necessary in conjunction with approved roads.

Disclaimer: These regulations may not be the most recent version. New Mexico may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.