Md. Code Regs. 26.20.26.02

Current through Register Vol. 51, No. 19, September 20, 2024

Section 26.20.26.02 - Valley Fills

A. Valley fills shall meet all of the general requirements for disposal of excess spoil and the additional requirements of this regulation.

B. The fill shall be designed to attain a long-term static safety factor of 1.5 based upon data obtained from subsurface exploration, geotechnical testing, foundation design, and accepted engineering analyses.

C. A subdrainage system for the fill shall be constructed in accordance with the following:

(1) A system of underdrains constructed of durable rock shall meet the following requirements:

(a) Be installed along the natural drainage system;

(b) Extend from the toe to the head of the fill; and

(c) Contain lateral drains to each area of potential drainage or seepage.

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

(3) In constructing the underdrains, not more than 10 percent of the rock may be less than 12 inches in size and no single rock may be larger than 25 percent of the width of the drain. The minimum size of the main underdrain shall be:

Total amount of fill material	Predominant type of fill material	Minimum size of drain, in feet
Width	Height
Less than 1,000,000 yards	Sandstone	10	4
Shale	16	8
More than 1,000,000 yards	Sandstone	16	8
Shale	16	16

(4) Underdrains shall consist of nondegradable, non-acid-forming or non-toxic-forming rock such as natural sand and gravel, sandstone, limestone, or other durable rock that will not slake in water and will be free of coal, clay, or shale.

D. Spoil shall be hauled or conveyed and placed in a controlled manner and concurrently compacted as specified by the Bureau, in lifts not greater than 4 feet or less if required by the Bureau to:

(1) Achieve the densities designed to ensure mass stability;

(2) Prevent mass movement;

(3) Avoid contamination of the rock underdrain or rock core; and

(4) Prevent formation of voids.

E. Surface water runoff from the area above the fill shall be diverted away from the fill and into stabilized diversion channels designed to pass safely the runoff from a 100-year, 24-hour precipitation event. Surface runoff from the fill surface shall be diverted to stabilized channels off the fill which will safely pass the runoff from a 100-year, 24-hour precipitation event.

F. The tops of the fill and any terrace constructed to stabilize the face shall be graded no steeper than 20:1. The vertical distance between terraces may not exceed 50 feet.

G. Drainage may not be directed over the outslope of the fill.

H. The outslope of the fill may not exceed 2:1.

Md. Code Regs. 26.20.26.02

Regulations .02 were previously codified as COMAR 08.13.09.32 a A_D, respectively. Recodification occurred in April, 1993. For a history of these regulations before April, 1993, see "Administrative History of COMAR 08.13.09 before April, 1993" which follows COMAR 26.20.01.