RELATES TO:
KRS
151.100,
151.250(3),
350.151,
350.425,
30 C.F.R. Parts 730-733, 735,
817.84,
917,
30 U.S.C. 1253,
1255,
1266
NECESSITY, FUNCTION, AND CONFORMITY:
KRS 350.028(1),
(5),
350.151(1),
and
350.465(2)
authorize the cabinet to promulgate administrative regulations relating to
surface and underground coal mining operations. This administrative regulation
establishes requirements for coal mine waste dams and impoundments for
underground mines. This administrative regulation differs from
30
CFR 817.84. Section 3(1)(b) of this
administrative regulation includes detailed requirements for principal
spillways in impoundments that do not have an open channel emergency spillway.
This is necessary to ensure the safety of a large impoundment that does not
have an open channel emergency spillways. Section 3(1)(c) of this
administrative regulation requires a minimum freeboard of three (3) feet that
is not included in the federal regulation. This is necessary to ensure the
safety of an impounding structure that may be susceptible to erosion if
overtopping occurs.
Section 1. General
Requirements.
(1) This administrative
regulation applies to dams and impoundments, constructed of coal mine waste or
intended to impound coal mine waste, that were completed or are to be completed
after August 3, 1977.
(2) Coal mine
waste shall not be used in the construction of dams and impoundments unless it
has been demonstrated to the cabinet that the stability of the structure
conforms with the requirements of Section 3(1) of this administrative
regulation. It shall also be demonstrated that the use of coal mine waste will
not have a detrimental effect on downstream water quality or the environment
due to acid seepage through the dam or impoundment. All demonstrations shall be
submitted to and approved by the cabinet.
(3) An impounding structure constructed of
coal mine waste or intended to impound coal mine waste shall not be retained
permanently as part of the approved postmining land use.
Section 2. Site Preparation. Before coal mine
waste is placed at a dam or impoundment site:
(1) All trees, shrubs, grasses, and other
organic material shall be cleared and grubbed from the site, and all
combustible materials shall be removed and disposed of or stockpiled in
accordance with the requirements of this chapter; and
(2) Surface drainage that may cause erosion
to the dam or the impoundment features, whether during construction or after
completion, shall be diverted away from the dam or impoundment by diversion
ditches that comply with the requirements of
405 KAR 18:080,
Section 1. Adequate outlets for discharge from these diversions shall be in
accordance with
405 KAR
18:060, Section 3. Diversions that are designed to
divert drainage from the upstream area away from the impoundment area shall be
designed to carry the peak run-off from a 100-year, six (6) hour precipitation
event. Twenty-four (24) hours may be used in lieu of six (6) hours for the
duration of the 100-year design precipitation event in this subsection. The
diversion shall be maintained to prevent blockage, and the discharges shall be
in accordance with
405 KAR
18:060, Section 3.
Section 3. Design and Construction.
(1) The design of each dam and impoundment
constructed of coal mine waste or intended to impound coal mine waste shall
comply with the requirements of
405 KAR
18:100, including the certification requirements
thereof, modified as follows:
(a) An
impounding structure constructed of coal mine waste or intended to impound coal
mine waste that meets the criteria of
30
CFR
77.216(a) shall have
sufficient spillway capacity to safely pass, adequate storage capacity to
safely contain, or a combination of storage capacity and spillway capacity to
safely control, the probable maximum precipitation of a six (6) hour
precipitation event. The cabinet may require a duration longer than six (6)
hours if safety concerns warrant a longer time period.
(b) An impounding structure with a drainage
area of ten (10) square miles or less that does not have an open channel
emergency spillway shall have a closed conduit principal spillway that shall
meet the requirements of this paragraph. The impounding structure shall have
sufficient storage capacity available to store the entire runoff from the
probable maximum precipitation event while maintaining the required freeboard
against overtopping, disregarding flow through the principal spillway.
1. The spillway shall have a trash rack
designed to provide positive protection against clogging of the spillway at all
operating levels, and an elbow designed to facilitate the passage of
trash;
2. The conduit shall be
large enough to pass the routed freeboard hydrograph peak discharge while
maintaining the required freeboard against overtopping the structure. For
structures included in paragraph (a) of this subsection, the probable maximum
precipitation event shall be used to determine the freeboard
hydrograph;
3. The conduit shall be
large enough to meet the requirements under
401 KAR
4:030 for minimum emergency spillway discharge
capacity; and
4. The spillway shall
meet all other applicable requirements under
401 KAR
4:030,
405 KAR
18:100, and this administrative regulation, except the
requirement under
401 KAR
4:030 that the conduit have a minimum cross-sectional
area of thirty-six (36) square feet. The cross-sectional area of the barrel of
the conduit shall be not less than twelve (12) square feet for a Class A
structure with a product of storage in acre-feet times effective height in feet
of less than 10,000 and shall be not less than twenty (20) square feet for
other structures.
(c)
The design freeboard between the lowest point on the dam or impoundment crest
and the maximum water elevation shall be at least three (3) feet. For
structures not included in paragraph (a) of this subsection, the maximum water
elevation shall be that determined by the freeboard hydro-graph criteria for
the appropriate structure hazard classification under
405 KAR
7:040, Section 5, and
401 KAR
4:030.
(d)
The dam or impoundment shall have a minimum safety factor of one and
five-tenths (1.5) for the partial pool with steady seepage saturation
conditions, and the seismic safety factor shall be at least one and two-tenths
(1.2).
(e) The dam or impoundment
foundation and abutments shall be designed to be stable under all conditions of
construction and operation of the impoundment. Sufficient foundation
investigations and laboratory testing shall be performed to determine the
safety factors of the dam or impoundment for all loading conditions required in
paragraph (d) of this subsection or
405 KAR
18:100, and for all increments of
construction.
(2)
Spillways and outlet works shall be designed to provide adequate protection
against erosion and corrosion. Inlets shall be protected against
blockage.
(3) Dams or impoundments
constructed of or impounding coal mine waste shall be designed so that at least
ninety (90) percent of the water stored during the design precipitation event
can be removed within a ten (10) day period.
Section 4. Operation. For a dam or
impoundment constructed of or impounding coal mine waste, at least ninety (90)
percent of the water stored during the design precipitation event shall be
removed within the ten (10) day period following the design precipitation
event.