N.M. Admin. Code § 19.8.20.2035 - DISPOSAL OF EXCESS SPOIL: VALLEY FILLS
Valley fills shall meet all of the requirements of 19.8.20.2034 NMAC and the additional requirements of 19.8.20 NMAC.
A. 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.
B. Unless the director
finds that a subdrainage system is not required for environmental protection, 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 requirements of Paragraph (4) of
Subsection B of
19.8.20.2035 NMAC and:
(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, the rock
size and size of the main underdrain will be designed to meet the conditions at
the site as determined by data called for in Subsection A of
19.8.20.2035 NMAC. If site
specific engineering design criteria are not submitted, the following criteria
will be used. In constructing the underdrains, no 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. Rock used in underdrains shall meet the
requirements of Paragraph (4) of Subsection B of
19.8.20.2035 NMAC. The minimum
size of the main underdrain shall be:
Total amount of Predominant type of Minimum size of
fill material fill material drain, in feet
Width Height
1,000,000 yd3 Sandstone 10 4
1,000,000 yd3 Shale 16 8
1,000,000 yd3 Sandstone 16 8
1,000,000 yd3 Shale 16 16
(4) Underdrains shall consist of
nondegradable, non-acid or 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.
C. Spoil shall be hauled or conveyed and
placed in a controlled manner and concurrently compacted as specified by the
director, in lifts no greater than 4 feet or less if required by the director
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.
D. 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, 6-hour
precipitation event or larger event specified by the director. 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, 6-hour precipitation event.
Diversion design shall comply with the requirements of
19.8.20.2011 NMAC.
E. The tops of the fill and any terrace
constructed to stabilize the face shall be graded no steeper than 1v:20h (5
percent). The vertical distance between terraces shall not exceed 50
feet.
F. Drainage shall not be
directed over the outslope of the fill.
G. The outslope of the fill shall not exceed
1v:2h (50 percent). The director may require a flatter
slope.
Notes
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