N.M. Admin. Code § 19.8.20.2036

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

Section 19.8.20.2036 - DISPOSAL OF EXCESS SPOIL: HEAD OF HOLLOW FILLS

Disposal of spoil in the head-of-hollow fill shall meet all standards set forth in 19.8.20.2034 and 2035 NMAC and the additional requirements of 19.8.20 NMAC.

A. The fill shall be designed to completely fill the disposal site to the approximate elevation of the ridgeline. A rock-core chimney drain may be utilized instead of the subdrain and surface diversion system required for valley fills. If the crest of the fill is not approximately at the same elevation as the low point of the adjacent ridgeline, the fill must be designed a specified in 19.8.20.2035 NMAC, with diversion of runoff around the fill. A fill associated with contour mining and placed at or near the coal seam, and which does not exceed 250,000 cubic yards may use the rock-core chimney drain.

B. The alternative rock-core chimney drain system shall be designed and incorporated into the construction of head-of-hollow fills as follows:

(1) The fill shall have, along the vertical projection of the main buried stream channel or rill a vertical core of durable rock at least 16 feet thick which shall extend from the toe of the fill to the head of the fill, and from the base of the fill to the surface of the fill. A system of lateral rock underdrains shall connect this rock-core to each area of potential drainage or seepage in the disposal area. Rocks used in the rock-core and underdrains shall meet the requirements of Subsection B of 19.8.20.2035 NMAC.

(2) A filter system to ensure the proper functioning of the rock-core shall be designed and constructed using standard geotechnical engineering methods.

(3) The grading may drain surface water away from the outslope of the fill and toward the rock-core. The maximum slope of the top of the fill shall be 1v:33h (3 percent). Instead of the requirements of Subsection G of 19.8.20.2034 NMAC, a drainage pocket may be maintained at the head of the fill during and after construction, to intercept surface runoff and discharge the runoff through or over the rock drain, if stability of the fill is not impaired. In no case shall this pocket or sump have a potential for impounding more than 10,000 cubic feet or water. Terraces on the fill shall be graded with a 3- to 5- percent grade toward the fill and a 1- percent slope toward the rock-core.

C. Other drainage control systems that have been demonstrated to provide equivalent stability to the fill as described in Subsections A and B of 19.8.20.2036 NMAC may be approved by the director.

D. The drainage control system shall be capable of passing safely the runoff from a 100-year, 24-hour precipitation event, or larger event specified by the director.

N.M. Admin. Code § 19.8.20.2036

11-29-97; 19.8.20.2036 NMAC - Rn, 19 NMAC 8.2.20.2036, 9-29-2000