Current through Register Vol. 35, No. 18, September 24, 2024
In order to achieve the approximate original contour, the
permittee shall, except as provided in this section, transport, backfill,
compact (where advisable to ensure stability or to prevent leaching of toxic
materials) and grade all spoil material to eliminate all highwalls, spoil piles
and depressions. Cut-and-fill terraces may be used only in those situations
expressly identified in this section. The postmining graded slopes must
approximate the premining natural slopes in the area as defined in paragraph
(a) [now Subsection A of 19.8.36.25 NMAC].
A. Slope measurements.
(1) To determine the natural slopes of the
area before mining, sufficient slopes to adequately represent the land surface
configuration, and as approved by the regulatory authority in accordance with
site conditions, must be accurately measured and recorded. Each measurement
shall consist of an angle of inclination along the prevailing slope extending
100 linear feet above and below or beyond the coal outcrop or the area to be
disturbed; or, where this is impractical, at locations specified by the
regulatory authority. Where the area has been previously mined, the
measurements shall extend at least 100 feet beyond the limits of mining
disturbances as determined by the regulatory authority to be representative of
the premining configuration of the land. Slope measurements shall take into
account natural variations in slope so as to provide accurate representation of
the range of natural slopes and shall reflect geomorphic differences of the
area to be disturbed. Slope measurements may be made from topographic maps
showing contour lines, having sufficient detail and accuracy consistent with
the submitted mining and reclamation plan.
(2) After the disturbed area has been graded,
the final graded slopes shall be measured at the beginning and end of lines
established on the prevailing slope at locations representative of premining
slope conditions and approved by the regulatory authority. These measurements
must not be made so as to allow unacceptably steep slopes to be
constructed.
B. Final
graded slopes.
(1) The final graded slopes
shall not exceed either the approximate premining slopes as determined
according to Paragraph (a)(1) [now Paragraph 1 of Subsection A of 19.8.36.25
NMAC] and approved by the regulatory authority or any lesser slope specified by
the regulatory authority based on consideration of soil, climate or other
characteristics of the surrounding area. Postmining final graded slopes need
not be uniform. The requirements of this paragraph may be modified by the
regulatory authority where the mining is reaffecting previously mined lands
that have not been restored to the standards of this section and sufficient
spoil is not available to return to the slope determined according to Paragraph
(a)(1) [now Paragraph 1 of Subsection A of 19.8.36.25 NMAC]. Where such
modifications are approved, the permittee shall, as a minimum, be required to:
(a) retain all overburden and spoil on the
solid portion of existing or new benches; and
(b) backfill and grade to the most moderate
slope possible to eliminate the highwall which does not exceed the angle of
repose or such lesser slopes as is necessary to assure stability.
(2) On approval by the regulatory
authority and in order to conserve soil moisture, ensure stability, and control
erosion on final graded slopes, cut-and-fill terraces may be allowed if the
terraces are compatible with the postmining land use approved under Section
715.13, and are appropriate substitutes for construction of lower grades on the
reclaimed lands. The terraces shall meet the following requirements:
(a) The width of the individual terrace bench
shall not exceed 20 feet unless specifically approved by the regulatory
authority as necessary for stability, erosion control or roads included in the
approved postmining land use plan.
(b) The vertical distance between terraces
shall be as specified by regulatory authority to prevent excessive erosion and
to provide long-term stability.
(c)
The slope of the terrace outslope shall not exceed 1v:2h (50 percent).
Outslopes which exceed 1v:2h (50 percent) may be approved if they have a
minimum static safety factor of more than 1.5 and provide adequate control over
erosion and closely resemble the surface configuration of the land prior to
mining. In no case may highwalls be left as part of terraces.
(d) Culverts and underground rock drains
shall be used on the terrace only when approved by the regulatory
authority.
(3) All
operations on steep slopes of 20 degrees or more or on such lesser slopes as
the regulatory authority defines as a steep slope shall meet the provisions of
Section 716.2 of this Chapter.
C. Mountaintop removal. The requirements of
this paragraph and of Section 716.3 shall apply to surface mining operations
which remove entire coal seams in the upper part of a mountain, ridge, or hill
by removing all of the overburden, and where the requirements for achieving the
approximate original contour of this section cannot be met. Final graded top
plateau slopes on the mined area shall be less than 1v:5h so as to create a
level plateau or gently rolling configuration and the outslopes of the plateau
shall not exceed 1v:2h, except where engineering data substantiates and the
regulatory authority finds that a minimum static safety factor of 1.5 (or
higher factors specified by the regulatory authority) will be attained.
Although the area need not be restored to approximate original contour, all
highwalls, spoil piles and depressions except as provided in Paragraphs (d) and
(e) [now Subsections D and E of 19.8.36.25 NMAC] of this section shall be
eliminated. All mountaintop removal operations shall in addition meet the
provisions of Section 716.3 of this Chapter.
D. Small depressions. The requirement of this
section to achieve approximate original contour does not prohibit construction
of small depressions if they are approved by the regulatory authority to
minimize erosion, conserve soil moisture or promote revegetation. These
depressions shall be compatible with the approved postmining land use and shall
not be inappropriate substitutes for construction of lower grade on the
reclaimed lands. Depressions approved under this section shall have a holding
capacity of less than one cubic yard of water or, if it is necessary that they
be larger, shall not restrict normal access throughout the area or constitute a
hazard. Large, permanent impoundments shall be governed by Paragraph (e) [now
Subsection E of 19.8.36.25 NMAC] of this Section and by Section
715.17.
E. Permanent impoundments.
Permanent impoundments may be retained in mined and reclaimed areas provided
all highwalls are eliminated by grading to appropriate contour and the
provisions for postmining land use (Section 715.13) and protection of the
hydrologic balance (Section 715.17) are met. No impoundments shall be
constructed on top of areas in which excess materials are deposited pursuant to
Section 715.15 of this part. Impoundments shall not be used to meet the
requirements of Paragraph (j) [now Subsection J of 19.8.36.25 NMAC] of this
Section.
F. Definition of thin and
thick restored overburden. The thin overburden provisions of Paragraph (g) [now
Subsection G of 19.8.36.25 NMAC] of this section may apply only where the final
thickness is less than 0.8 of the initial thickness. The thick overburden
provisions of Paragraph (h) [now Subsection H of 19.8.36.25 NMAC] of this
section may apply only where the final thickness is greater than 1.2 of the
initial thickness. Initial thickness is the sum of the overburden thickness and
coal thickness. Final thickness is the product of the overburden thickness
times the bulking factor to be determined for each mine area. The provisions of
Paragraph (g) and (h) [now Subsection G and H of 19.8.36.25 NMAC] apply only
when operations cannot be carried out to comply with the requirements of
Paragraph (a) [now Subsection A of 19.8.36.25 NMAC] of this section to achieve
the approximate original contour.
G. Thin overburden. In surface coal mining
operations carried out continuously in the same limited pit area for more than
one year from the day coal-removal operations begin and where the volume of all
available spoil and suitable waste materials is demonstrated to be insufficient
to achieve approximate original contour, surface coal mining operations shall
be conducted to meet, at a minimum, the following standards:
(1) Transport, backfill and grade, using all
available spoil and suitable waste materials from the entire mine area, to
attain the lowest practicable stable grade, which may not exceed the angle of
repose, and to provide adequate drainage and long-term stability of the
regraded areas.
(2) Eliminate
highwalls by grading or backfilling to stable slopes not exceeding lv:2h (50
percent), or such lesser slopes as the regulatory authority may specify to
reduce erosion, maintain the hydrologic balance, or allow the approved
postmining land use.
(3) Transport,
backfill, grade and revegetate to achieve an ecologically sound land use
compatible with the prevailing land use in unmined areas surrounding the permit
area.
(4) Transport, backfill, and
grade to ensure the impoundments are constructed only where it has been
demonstrated to the regulatory authority's satisfaction that all requirements
of Section 715.17 have been met and that the impoundments have been approved by
the regulatory authority as meeting the requirements of this Part and all other
applicable federal and state regulations.
H. Thick overburden. In surface coal mining
operations where the volume of spoil is demonstrated to be more than sufficient
to achieve the approximate original contour surface coal mining operations
shall be conducted to meet at a minimum the following standards:
(1) Transport, backfill and grade all spoil
and wastes not required to achieve approximate original contour in the surface
mining area to the lowest practicable grade.
(2) Deposit, backfill and grade excess spoil
and wastes only within the permit area and dispose of such materials in
conformance with this part.
(3)
Transport, backfill and grade excess spoil and wastes to maintain the
hydrologic balance in accordance with this part and to provide long-term
stability.
(4) Transport, backfill,
grade and revegetate wastes and excess spoil to achieve an ecologically sound
land use compatible with the prevailing land uses in unmined areas surrounding
the permit area.
(5) Eliminate all
highwalls and depressions except as stated in Paragraph (e) [now Subsection E
of 19.8.36.25 NMAC] of this Section by backfilling with spoil and suitable
waste materials.
I.
Regrading or stabilizing rills and gullies. When rills or gullies deeper than
nine inches form in areas that have been regraded and the topsoil replaced but
vegetation has not yet been established the permittee shall fill, grade, or
otherwise stabilize the rills and gullies and reseed or replant the areas
according to Section 715.20. The regulatory authority shall specify that rills
or gullies of lesser size be stabilized if the rills or gullies will be
disruptive to the approved postmining land use or may result in additional
erosion and sedimentation.
J.
Covering coal and acid-forming, toxic-forming, combustible and other waste
materials; stabilizing backfilled materials; and using waste material for fill.
(1) Cover all exposed coal seams remaining
after mining and any acid-forming, toxic-forming, combustible materials, or any
other waste materials identified by the regulatory authority that are exposed,
used or produced during mining shall be covered with a minimum of four feet of
nontoxic and noncombustible material; or, if necessary, treated to neutralize
toxicity in order to prevent water pollution and sustained combustion, and to
minimize adverse effects on plant growth and land uses. Where necessary to
protect against upward migration of salts, exposure by erosion, to provide an
adequate depth for plant growth or to otherwise meet local conditions, the
regulatory authority shall specify thicker amounts of cover using nontoxic
material. Acid-forming or toxic-forming material shall not be buried or stored
in proximity to a drainage course so as to cause or pose a threat of water
pollution or otherwise violate the provisions of Section 715.17 of this
Part.
(2) Stabilization. Backfilled
materials shall be selectively placed and compacted wherever necessary to
prevent leaching of toxic-forming materials into surface or subsurface waters
in accordance with Section 715.17 and wherever necessary to ensure the
stability of the backfilled materials. The method of compacting material and
the design specifications shall be approved by the regulatory authority before
the toxic materials are covered.
(3) Use of waste materials as fill. Before
waste materials from a coal preparation or conversion facility or from other
activities conducted outside the permit area such as municipal wastes are used
for fill material, it must be demonstrated to the regulatory authority by
hydrogeological means and chemical and physical analyses that use of these
materials will not adversely affect water quality, water flow and vegetation;
will not present hazards to public health and safety; and will not cause
instability in the backfilled area.
K. Grading along the contour. All final
grading, preparation of overburden before replacement of topsoil and placement
of topsoil, in accordance with Section 715.16 shall be done along the contour
to minimize subsequent erosion and instability. If such grading, preparation or
placement along the contour would be hazardous to equipment operators then
grading, preparation or placement in a direction other than generally parallel
to the contour may be used. In all cases, grading, preparation or placement
shall be conducted in a manner which minimizes erosion and provides a surface
for replacement of topsoil which will minimize slippage.
