16 Tex. Admin. Code § 12.364 - Disposal of Excess Spoil: Valley Fills
(a) Valley fills shall meet all of the
requirements of §
12.363 of this title (relating to
Disposal of Excess Spoil: General Requirements) and the additional requirements
of this section.
(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 requirements of paragraph (4) of this subsection
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 ensure the proper
functioning of the rock underdrain system shall be designed and constructed
using standard geotechnical engineering methods;
(3) in constructing the underdrains, no more
than 10% of the rock may be less than 12 inches in size, and no single rock may
be larger than 25% of the width of the drain. Rock used in underdrains shall
meet the requirements of paragraph (4) of this subsection. The minimum size of
the main underdrain shall be:
(4)
underdrains shall consist of nondegradable, non-acid-forming and
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 Commission, in lifts no greater than 4 feet, or
less if required by the Commission, to:
(1)
achieve the densities designed to ensure mass stability;
(2) prevent mass movements;
(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 or larger event specified by the Commission. 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.
Diversion designs shall comply with the requirements of §
12.341(6) of
this title (relating to Hydrologic Balance: Diversions).
(f) The tops of the fill and any terrace
constructed to stabilize the face shall be graded no steeper than 20h:1v (5%).
The vertical distance between terraces shall not exceed 50 feet.
(g) Drainage shall not be directed over the
outslope of the fill.
(h) The
outslope of the fill shall not exceed 2h:1v (50%). The Commission may require a
flatter slope.
Notes
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