NECESSITY, FUNCTION, AND CONFORMITY: KRS Chapter 350 in
pertinent part, requires the cabinet to promulgate administrative regulations
pertaining to noncoal mineral operations to minimize their adverse effects on
the citizens and the environment of the Commonwealth. This administrative
regulation sets forth provisions for impoundments.
Section 1. Requirements for Permanent and
Temporary Impoundments.
(1) Design
certification. The design of impoundments shall be certified by a qualified
registered professional engineer as designed to meet the requirements of this
administrative regulation using current, prudent engineering practices, and any
design criteria established by the cabinet. The qualified registered
professional engineer shall be experienced in the design and construction of
impoundments.
(2) All impoundments
classified as Class B-moderate hazard or Class C-high hazard, and all permanent
"dams," as defined in
KRS
151.100, shall comply with
401 KAR
4:030. Criteria for the hazard classifications are
established by
401 KAR
4:030.
(3)
Stability.
(a)
1. Permanent and temporary "dams" (as defined
in
KRS
151.100), permanent and temporary Class B and
C impoundments, and all permanent impoundments, shall have a minimum static
safety factor of 1.5 for the normal pool with steady seepage saturation
conditions, and a seismic safety factor of at least one and two-tenths
(1.2).
2. Impoundments not included
in subparagraph 1 of this paragraph shall have a minimum static safety factor
of one and three-tenths (1.3) for the normal pool with steady state seepage
saturation conditions.
(b) The constructed height of the dam shall
be increased a minimum of five (5) percent over the design height to allow for
settlement, unless it has been demonstrated to the cabinet that the material
used and the design will ensure against all settlement.
(c) The minimum top width of the embankment
shall not be less than the quotient of (H+35)/5, where H is the height, in
feet, of the embankment as measured from the upstream toe of the embankment to
the top of the embankment.
(d)
Unless the cabinet approves steeper slopes, based upon a satisfactory
demonstration of stability by the applicant acceptable to the cabinet, the sum
of the upstream and downstream side slopes (h/v) of the settled embankment
shall not be less than 5h:1v, with neither slope steeper than 2h:1v. Slopes
shall be designed to be stable in all cases, even if flatter side slopes are
required.
(e) The fill material
shall be free of sod, large roots, other large vegetative matter, and frozen
soil.
(f) The placing and spreading
of fill material shall be started at the lowest point of the foundation. The
fill shall be brought up in horizontal layers of such thickness as is required
to facilitate compaction and meet the design requirement of this administrative
regulation. Compaction shall be conducted as specified in the design approved
by the cabinet.
(g) The entire
embankment including the surrounding areas disturbed by construction shall be
stabilized with respect to erosion by a vegetative cover or other means
immediately after the embankment is completed. The active upstream face of the
embankment where water will be impounded may be riprapped or otherwise
stabilized and no vegetative cover is needed. Areas in which the vegetation is
not successful or where rills and gullies develop shall be repaired and
revegetated.
(h) Slope protection
shall be provided to protect against surface erosion at the site and protect
against sudden drawdown.
(i)
Measures shall be taken to control seepage in order to ensure stability of the
embankment.
(4)
Freeboard. Impoundments shall have adequate freeboard to resist overtopping by
waves and by sudden increases in storage volume. The minimum elevation at the
top of the settled embankment shall be one (1.0) foot above the water surface
in the impoundment with the emergency spillway flowing at design depth. For
embankments subject to settlement, this one (1.0) foot minimum elevation
requirement shall apply at all times, including the period after settlement.
Freeboard requirements shall not apply to incised impoundments which have no
embankment or levee.
(5)
Foundation.
(a)
1. Foundation and abutments for the
impounding structure shall be designed to be stable under all conditions of
construction and operation of the impoundment and shall be designed based on
adequate and accurate information on the foundation conditions.
2. For permanent and temporary "dams" (as
defined in
KRS
151.100), for permanent and temporary Class B
and C impoundments, and for all permanent impoundments, foundation
investigations as well as any necessary laboratory testing of materials shall
be performed in order to determine the design requirements for foundation and
embankment stability.
3. Where an
approved temporary impoundment has been constructed and the mineral permittee
subsequently seeks a permit revision to upgrade the structure to a permanent
impoundment, the cabinet may waive the foundation investigations and laboratory
testing required by subparagraph 2 of this paragraph under the following
circumstances:
a. The structure has been
recently verified as being a Class A-low hazard structure;
b. The structure does not meet the definition
of the term "dam," as defined at
KRS
151.100; and
c. The cabinet approves conservative, assumed
values for the strength parameters used in the stability analyses to ensure
compliance with subsection (3)(a) of this section.
(b) All vegetative and organic
materials shall be removed and foundations excavated and prepared to resist
failure. Cutoff trenches shall be installed if necessary to ensure
stability.
(6)
Spillways. Impoundments shall include a combination of principal and emergency
spillways which shall be designed and constructed to safely pass the design
precipitation event specified in this subsection, unless the cabinet requires a
larger event. Twenty-four (24) hours may be used in lieu of six (6) hours for
the duration of a design precipitation event specified in this subsection.
(a) Class A impoundments that are not "dams"
(as defined in
KRS
151.100) shall pass the:
1. Twenty-five (25) year, six (6) hour
precipitation event if it is a temporary impoundment; or
2. The fifty (50) year, six (6) hour
precipitation event if it is a permanent impoundment.
(b) Temporary Class A impoundments that are
"dams" (as defined in
KRS
151.100) shall pass the 100 year, six (6)
hour precipitation event.
(c)
Permanent and temporary Class B and C impoundments and all permanent "dams" (as
defined in
KRS
151.100) shall comply with the criteria
established in
401 KAR
4:030.
(d)
Emergency spillway grades and allowable velocities shall be approved by the
cabinet.
(7) Single
spillway. Class A impoundments that are not "dams" (as defined in
KRS
151.100) may use a single spillway if the
spillway:
(a) Is an open channel of
nonerodible construction and capable of maintaining sustained flows;
and
(b) Is not earth or grass
lined.
(8) Temporary
impoundments existing on the effective date of this administrative regulation
that are, and continue to be, Class A hazard, shall not be required to be
modified to meet the requirements of subsections (1) through (7) of this
section unless the cabinet, based upon an inspection, determines that
modification to meet some or all of these requirements is necessary to protect
the public health or safety or to protect the environment.
(9) Emergency procedures. If any examination
or inspection of an impoundment discloses that a potential hazard exists, the
person who examined the impoundment shall immediately notify the department and
the Kentucky Division of Water, or if these agencies cannot be reached,
Disaster and Emergency Services. The mineral permittee shall immediately
implement emergency procedures formulated for public protection and remedial
action. If adequate emergency procedures cannot be formulated or implemented by
the mineral permittee, the cabinet shall be notified, and the cabinet shall
notify the appropriate agencies that other emergency procedures are required to
protect the public.
Section
2. Additional Requirements for Permanent Impoundments.
(1) General.
(a) The retention of a permanent impoundment
is subject to the approval of the cabinet.
(b) Permanent pit impoundments with no
embankment are encouraged.
(c) It
shall be demonstrated to the cabinet's satisfaction that adequate sources of
water are available to maintain the water level of the impoundment at a
reasonable elevation at all times. Adequate sources of water supply for
impoundments may be from springs, drainage areas of sufficient size,
groundwater percolation, a flowing stream, or any combination of these
sources.
(d) In accordance with 405
KAR
5:030, if a permanent impoundment is proposed, an affidavit from the
landowner approving the impoundment and acknowledging that the mineral
permittee will have no continuing maintenance responsibility after permit
release, is required, except for final pit impoundments with no
embankment.
(e) Permanent
impoundments shall be demonstrated to be a part of the approved postmining land
use.
(2) If a permanent
impoundment is proposed, the following stipulations shall be met:
(a) Adequate means of access, such as roads
or ramps, are left or provided to the water impoundment.
(b) A terrace shall be provided above, but in
near proximity to, the high water level of the permanent impoundment, except on
the portion of the impoundment comprising the highwall of the pit.
(c) Any spoil above the terrace shall be
graded until it is rounded off and blended into the area contour above the
terrace.
(d) All spoil piles
adjoining access roads to permanent impoundments shall be graded to minimize
erosion and blend into the surrounding area.
(e) The angle of the slope from the roadbed
to the top of the spoil may be greater than the surrounding area if adequate
drainage measures are taken to prevent erosion of the slope, including but not
limited to, terracing and vegetation.
(f) The roadbed shall be adequately drained
and culverts shall be provided so as to prevent it from being eroded.
(g) The area above the highwall on any
permanent water impoundment shall be protected by a landscape barrier or a
fence approved by the Department for Natural Resources.