Current through Register Vol. 35, No. 18, September 24, 2024
A. Permanent impoundments are prohibited
unless authorized by the director, upon the basis of the following
demonstrations:
(1) the size and
configuration of such impoundment will be adequate for its intended
purposes;
(2) the quality of
impounded water will be suitable on a permanent basis for its intended use and,
after reclamation, will meet applicable state and federal water quality
standards, and discharges from the impoundment will meet applicable effluent
limitations and will not degrade the quality of receiving water below
applicable state and federal water quality standards;
(3) the water level will be sufficiently
stable and be capable of supporting the intended use;
(4) final grading will provide for adequate
safety and access for proposed water users;
(5) the impoundment will not result in the
diminution of the quality and quantity of water utilized by adjacent or
surrounding landowners for agricultural, industrial, recreational, or domestic
uses; and
(6) the impoundment will
be suitable for the approved postmining land use.
B. The design of impoundments shall be
certified by a qualified registered professional engineer as designed to meet
the requirements of 19.8.20 NMAC using current, prudent engineering practices,
and any design criteria established by the director. The qualified registered
professional engineer shall be experienced in the design and construction of
impoundments.
C. An impoundment
meeting the size or other criteria of
30
CFR 77.216(a) shall comply
with the requirements of
30
CFR 77.216 and 19.8.20 NMAC.
D. All impoundments that meet the class B or
C criteria for dams in TR-60 or exceed the size or other criteria of
30
CFR 77.216(a) shall be
certified to the director by a qualified registered professional engineer, as
having been constructed to comply with the requirements of 19.8.20 NMAC. All
dams and embankments that do not meet the class B or C criteria for dams in
TR-60 or other size criteria of
30
CFR 77.216(a) shall be
certified by either a qualified registered professional engineer or a qualified
registered professional land surveyor, except that all coal processing waste
dams and embankments covered by 19.8.20.2047 through 2049 NMAC shall be
certified by a qualified registered professional engineer. All impoundments
shall be certified after construction and prior to the intended use.
E. The following is a list of general
requirements that apply to all temporary or permanent impoundments.
(1) Impoundments meeting the class B or C
criteria for dams in the U.S. department of agriculture, natural resources
conservation service technical release no. 60 (210-VI-TR60, Oct. 1985), "earth
dams and reservoirs", shall comply with the, "minimum emergency spillway
hydrologic criteria", table in TR-60 and the requirements of 19.8.20
NMAC.
(2) An impoundment meeting
the Class B or C criteria for dams in NRCS technical release no. 60
(210-VI-TR60, Oct. 1985), "earth dams and reservoirs", or the size or other
criteria of
30
CFR 77.216(a) shall have a
minimum static safety factor of 1.5 for a normal pool with steady state seepage
saturation conditions, and a seismic safety factor of at least 1.2.
(3) Impoundments not included in Paragraph
(2) of Subsection E of 19.8.20.2017 NMAC, except for a coal mine waste
impounding structure, shall have a minimum static safety factor of 1.3 for a
normal pool with steady state seepage saturation conditions or meet the
requirements of Subsection C of 19.8.9.909 NMAC.
(4) Impoundments meeting the class B or C
criteria for dams in NRCS technical release no. 60 (210-VI-TR60, Oct. 1985),
"earth dams and reservoirs", shall comply with the freeboard hydrograph
criteria in the "minimum emergency spillway hydrologic criteria" table in
TR-60.
(5) Impoundments not
included in Paragraph (2) of Subsection E of 19.8.20.2017 NMAC shall have
adequate freeboard to resist overtopping by waves and by a sudden increase in
stored volume.
(6) Foundations and
abutments for an impounding structure shall be stable during all phases of
construction and operation, and shall be designed based on adequate and
accurate information on the foundation conditions. For an impoundment meeting
the class B or C criteria for dams in NRCS technical release no. 60
(210-VI-TR60, Oct. 1985), "earth dams and reservoirs", or the size or other
criteria of
30
CFR 77.216(a), foundation
investigation, as well as any necessary laboratory testing of foundation
material, shall be performed to determine the design requirements for
foundation stability.
(7) 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.
(8) Slope
protection shall be provided to protect against surface erosion where surface
runoff enters the impoundment area and protect against sudden
drawdown.
(9) Faces of embankments
and surrounding areas shall be vegetated, or otherwise stabilized in accordance
with accepted design and operational practices.
(10) The vertical portion of any remaining
highwall shall be located far enough below the low-water line along the full
extend of highwall to provide adequate safety and access for the proposed water
users.
(11) Appropriate barriers
shall be provided to control seepage along conduits that extend through the
embankment.
F. An
impoundment shall include either a combination of principal and emergency
spillways or a single spillway configured as specified in Paragraph (1) of
Subsection F of 19.8.20.2017 NMAC, designed and constructed to safely pass the
applicable design precipitation runoff event specified in Paragraph (2) of
Subsection F of 19.8.20.2017 NMAC, except as set forth in Paragraph (3) of
Subsection F of 19.8.20.2017 NMAC.
(1) The
director may approve a single open-channel spillway that is:
(a) of nonerodible construction and designed
to carry sustained flows; or
(b)
earth- or grass-lined and designed to carry short-term, infrequent flows at
non-erosive velocities where sustained flows are not expected.
(2) Except as specified in
Paragraph (3) of Subsection F of 19.8.20.2017 NMAC, the required design
precipitation event for spillways for impoundments is:
(a) for an impoundment meeting the class B or
C criteria for dams in TR-60 or other size criteria of
30
CFR 77.216(a), a 100-year
6-hour event, or greater event as specified by the director.
(b) for a temporary impoundment not meeting
the class B or C criteria for dams in TR-60 or other size criteria of
30
CFR 77.216(a), a 25-year
6-hour event, or greater event as specified by the director.
(c) for a permanent impoundment not meeting
the class B or C criteria for dams in TR-60 or other size criteria of
30
CFR 77.216(a), a 50-year,
6-hour event, or greater event as specified by the director.
(3) In lieu of meeting the
requirements in Paragraph (1) of Subsection F of 19.8.20.2017 NMAC, the
director may approve a temporary impoundment that relies primarily on storage
to control the runoff from the design precipitation event when it is
demonstrated by the operator and certified by a qualified registered
professional engineer or qualified registered professional land surveyor that
the impoundment will safely control the design precipitation event and
associated runoff, the water from which shall be safely removed in accordance
with current, prudent, engineering practices. Such an impoundment shall be
located where failure would not be expected to cause loss of life or serious
property damage. The following design criteria shall apply:
(a) in the case of an impoundment meeting the
size or other criteria of
30
CFR 77.216(a), it is
designed to control the runoff of the probable maximum precipitation of a
6-hour event, or greater event as specified by the director, or
(b) in the case of an impoundment not meeting
the size or other criteria of
30
CFR 77.216(a), it is
designed to control the runoff of a 100-year 6-hour event, or greater event as
specified by the director.
G. Except as provided in Paragraph (4) of
Subsection G of 19.8.20.2017 NMAC, a qualified registered professional engineer
or other qualified professional specialist under the direction of a
professional engineer, shall inspect each impoundment as provided in Paragraph
(1) of Subsection G of 19.8.20.2017 NMAC. The professional engineer or
specialist shall be experienced in the construction of impoundments.
(1) Inspections shall be made regularly
during construction, upon completion of construction, and at least yearly until
removal of the structure or release of the performance bond.
(2) The qualified registered professional
engineer, or qualified registered professional land surveyor as specified in
Paragraph (4) of Subsection G of 19.8.20.2017 NMAC, shall promptly after each
inspection required in Paragraph (1) of Subsection G of 19.8.20.2017 provide to
the director a certified report that the impoundment has been constructed
and/or maintained as designed and in accordance with the approved plan and
19.8.20 NMAC. The report shall include discussion of any appearance of
instability, structural weakness or other hazardous conditions, depth and
elevation of any impounded waters, existing storage capacity, any existing or
required monitoring procedures and instrumentation, and any other aspects of
the structure affecting stability.
(3) A copy of the report shall be retained at
or near the mine site.
(4) A
qualified registered professional land surveyor may inspect any temporary or
permanent impoundment that does not meet the class B or C criteria for dams in
TR-60 or other size criteria of
30
CFR 77.216(a) and certify
and submit the report required by Paragraph (2) of Subsection G of 19.8.20.2017
NMAC, except that all coal mine waste impounding structures covered by
19.8.20.2047 through 2049 NMAC shall be certified by a qualified registered
professional engineer. The professional land surveyor shall be experienced in
the construction of impoundments.
(5) Impoundments meeting the class B or C
criteria for dams in TR-60 or subject to
30
CFR 77.216(a) must be
examined in accordance with
30
CFR 77.216-3. Other impoundments shall be
examined at least quarterly by a qualified person designated by the operator
for appearance of structural weakness and other hazardous conditions.
(6) If an impoundment is constructed without
an embankment, the director may waive the quarterly examination requirement.
Therefore, excavated ponds, haulroad sumps and any impoundment that is built
without embankments may be exempt from the requirements of Paragraph (5) of
Subsection G of 19.8.20.2017 NMAC with the approval of the director. Any waiver
granted under this paragraph shall not relieve the operator of the requirement
to maintain impoundments in accordance with the approved plan and 19.8.20
NMAC.
(7) Emergency procedures. If
any examination or inspection discloses that a potential hazard exists, the
person who examined the impoundment shall promptly inform the director of the
finding and of the emergency procedures formulated for public protection and
remedial action. If adequate procedures can not be formulated or implemented,
the director shall be notified immediately. The director shall then notify the
appropriate agencies that other emergency procedures are required to protect
the public.
