Kentucky Administrative Regulations › Title 405 - ENERGY AND ENVIRONMENT CABINET - DEPARTMENT FOR NATURAL RESOURCES › Chapter 5 - Surface Effects of Noncoal Mining › Section 405 KAR 5:055 - Permanent and temporary impoundments

Current through Register Vol. 51, No. 1, July 1, 2024
RELATES TO:
				KRS
				350.010(2),
				350.240,
				350.300
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.