La. Admin. Code tit. 43 § XV-5371

Current through Register Vol. 50, No. 11, November 20, 2024

Section XV-5371 - Disposal of Excess Spoil: Durable Rock Fills

A. In lieu of the requirements of §5367 and 5369, the office may approve alternate methods for disposal of hard rock spoil, including fill placement of 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 this Section and §5365 are met. For this Section, hard rock spoil shall be defined as rockfill consisting of at least 80 percent by volume of durable, non-acid- and non-toxic-forming rock (e.g., sandstone or limestone) that does not slake in water and will not degrade to soil material. Resistance of the hard rock spoil to slaking shall be determined by using the slake index and slake durability tests in accordance with guidelines and criteria established by the office.

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

a. The method of spoil placement shall be designed to ensure mass stability and prevent mass movement in accordance with the additional requirements of this Section.

b. 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 engineer and approved by the office.

2.

a. 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.

b. 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

3. The design of a head-of-hollow fill shall include an internal drainage system which will insure continued free drainage of anticipated seepage from precipitation and from springs or wet weather seeps.

a. 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.

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

c. The internal drain shall be protected by a properly designed filter system.

4. 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, 6-hour precipitation event. Diversion design shall comply with the requirements of §5323

5. 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.

6. 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, 6-hour precipitation event. Diversion design shall comply with the requirements of §5323

7. Terraces shall be constructed on the outslope if required for control of erosion or for roads included in the approved post-mining land use plan. Terraces shall meet the following requirements.

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

b. 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.

c. Terrace ditches shall have a five percent slope toward the channel specified in §5371. A 6, unless steeper slopes are necessary in conjunction with approved roads.

La. Admin. Code tit. 43, § XV-5371

Promulgated by the Department of Natural Resources, Office of Conservation, LR 5:395 (December 1979), amended LR 14:441 (July 1988), LR 20:447 (April 1994).

AUTHORITY NOTE: Promulgated in accordance with R.S. 30:901-932.