Chapter 21. Ponds and Sediment Control Measures

Flow is infrequent and presents small and infrequent treatment requirements to meet applicable standards which do not require use of an automatic neutralization process; and

Timely and consistent treatment is ensured.

Temporary diversions shall be constructed to pass safely the peak runoff from a 2-year, 24-hour precipitation event with sufficient freeboard to pass a 10-year, 24-hour precipitation event or a larger event as specified by the Bureau.

To protect fills and property and to avoid danger to public health and safety, permanent diversion shall be constructed to pass safely the peak runoff from a 10-year, 24-hour precipitation event, or a larger event as specified by the Bureau. Permanent diversions shall be constructed with gently sloping banks that are stabilized by vegetation. Asphalt, concrete, or other similar linings shall be used only when approved by the Bureau to prevent seepage or to provide stability.

Diversions shall be designed, constructed, and maintained in a manner which prevents additional contributions of suspended solids to streamflow and to runoff outside the permit area, to the extent possible using the best technology currently available. Appropriate sediment control measures for the diversions may include, but not be limited to, maintenance of appropriate gradients, channel lining, revegetation, roughness structures, and detention basins.

A diversion may not be located so as to increase the potential for landslides. A diversion may not be constructed on existing landslides, unless approved by the Bureau.

When no longer needed, each temporary diversion shall be removed and the affected land regraded, topsoiled, and revegetated.

Diversions shall be designed to minimize adverse impacts to the hydrologic balance within the permit and adjacent areas, to prevent material damage outside the permit area, and to assure the safety of the public.

Channel lining shall be designed using standard engineering practices to pass safely the design velocities.

Freeboard shall be not less than 1 foot. Protection shall be provided for transition of flows and for critical areas such as swales and curves. Where the area protected is a critical area as determined by the Bureau, the design freeboard may be increased.

Energy dissipators shall be installed when necessary at discharge points, where diversions intersect with natural streams and exit velocity of the diversion ditch flow is greater than that of the receiving stream.

Excess excavated material not necessary for diversion channel geometry or regarding of the channel shall be disposed of.

Topsoil shall be handled in accordance with the Regulatory Program.

Diversions may not be constructed or operated to divert water into underground mines without the approval of the Bureau.

Are approved by the Bureau after making a finding that the diversion will not adversely affect the water quantity and quality and related environmental resources of the stream;

Comply with other requirements of this regulation; and

Comply with local, State, and federal statutes and regulations.

The longitudinal profile of the stream, the channel, and the floodplain shall be designed and constructed to remain stable and, to the extent possible using the best currently available technology, to prevent additional contributions of suspended solids to streamflow or to runoff outside the permit area. These contributions may not be in excess of requirements of State or federal law. Erosion control structures such as channel lining structures, retention basins, and artificial channel roughness structures shall be used in diversions only when approved by the Bureau as being necessary to control erosion. These structures shall be approved for permanent diversions only where they are stable and will require infrequent maintenance.

The combination of channel, bank, and floodplain configurations shall be adequate to pass safely the peak runoff of a 10-year, 24-hour precipitation event for temporary diversions, a 100-year, 24-hour precipitation event for permanent diversions, or larger events specified by the Bureau. However, the capacity of the channel itself should be at least equal to the capacity of the unmodified stream channel immediately upstream and downstream of the diversion.

The design and construction shall be certified by a qualified professional engineer as meeting the design criteria of the Regulatory Program.

Restore, enhance where practicable, or maintain natural riparian vegetation on the banks of the stream;

Establish or restore the stream to its natural meandering shape or an environmentally acceptable gradient, as determined by the Bureau; and

Establish or restore the stream to a longitudinal profile and cross section, including aquatic habitats that approximate pre-mining stream channel characteristics.

Prevent, to the extent possible, additional contributions of sediment to streamflow or to runoff outside the permit area;

Meet the more stringent of applicable State or federal effluent limitations; and

Minimize erosion to the extent possible.

Disturbing the smallest practicable area at any one time during the mining operation through progressive backfilling, grading, and prompt revegetation;

Diverting runoff away from disturbed areas;

Diverting runoff using protected channels or pipes through disturbed areas so as not to cause additional erosion;

Using straw dikes, riprap, check dams, mulches, vegetative sediment filters, and other measures that reduce overland flow velocity, reduce runoff volume, or trap sediment;

Treating with chemicals.

Disturbed drainage area within the total disturbed area is small; and

Operator demonstrates that siltation structures and alternate sediment control measures are not necessary to meet the effluent limitations in this chapter and the applicable State and federal water quality standards for receiving waters.

Disturbed Area.

“Other treatment facilities” means any chemical treatments, such as flocculation, or mechanical structures, such as clarifiers, that have a point source discharge and that are utilized to prevent additional contribution of suspended solids to streamflow or runoff outside the permit area.

“Siltation structure” means a sedimentation pond, a series of sedimentation ponds, or other treatment facility.

Shall prevent additional contributions of suspended solids sediment to streamflow or runoff outside the permit area to the extent possible using the best technology currently available;

Shall collect all surface drainage from the disturbed area before leaving the permit area, except as provided in §A of this regulation;

Shall be constructed before beginning a surface mining activity in an area and, upon construction, be certified by a qualified professional engineer as being constructed in accordance with the approved design;

Shall be designed, constructed, and maintained in accordance with Regulation .08 of this chapter if the structure impounds water;

Shall be maintained until:

May not be removed if augmented seeding has occurred within the last 2 years.

Designed, constructed, and maintained in accordance with Regulation .08 of this chapter;

Located as near as possible to the disturbed area and out of perennial streams, unless approved by the Bureau; and

Designed, constructed, and maintained to:

In accordance with the applicable requirements of this section; and

To contain or treat the 10-year, 24-hour precipitation event unless a lesser design event is approved by the Bureau in accordance with §G(3)(c) of this regulation.

Compliance with USDA, Natural Resources Conservation Service, Maryland Conservation Practice, Standard Pond Code 378 (January 2000), as incorporated by reference in COMAR 26.17.02.01-1B(2);

Compliance with requirements of COMAR 26.17.04.05 if the embankment is more than 15 feet in height as measured from the upstream toe of the embankment to the crest of the emergency spillway;

Impoundments meeting the Class (b) or (c) criteria for dams in “Earth Dams and Reservoirs”, TR-60 shall comply with “Minimum Emergency Spillway Hydrologic Criteria” table in TR-60 and the requirements of this regulation;

The minimum elevation at the top of the settled embankment shall be 1 foot above the water surface in the pond with the emergency spillway flowing at design depth;

The height of the embankment is a minimum of 5 percent over the design height to allow for settlement, unless it has been demonstrated to the Bureau that the material used and the design will ensure against all settlement;

The top width of the embankment is not less than the quotient of (H+35)/5, when H is the height, in feet, of the embankment, as measured from the upstream toe of the embankment;

Perimeter slopes are stable, are not steeper than 2:1, and are protected against erosion where water enters the impoundment;

The combined upstream and downstream side slopes of the settled embankment are not less than 5:1 with neither slope steeper than 2:1;

The crest of the emergency spillway is a minimum of 1 foot above the crest of the principal spillway;

A cut-off trench is installed before initiating the placement of fill material for the embankment with side slopes not steeper than 1:1;

The embankment foundation area is cleared of all organic material and the entire area scarified;

The embankment begins by placing and spreading fill material at the lowest point of the foundation, is brought up in horizontal layers not to exceed 8 inches as required to facilitate compaction, and is compacted as specified in the design approved by the Bureau;

Fill material used in the construction of the embankment is free of sod, large roots and other vegetative matter, frozen soil, and coal processing waste;

The embankment slope is protected against surface erosion and against damage caused by sudden drawdown;

The embankment faces and surrounding areas are vegetated, except that the faces where water is impounded may be riprapped or otherwise stabilized in accordance with accepted design practices; and

Newly constructed areas and those areas disturbed by the construction are vegetated immediately upon completion of the construction.

Impoundments meeting the Class (b) or (c) criteria for dams contained in “Earth Dams and Reservoirs”, TR-60 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.

Impounds not included in §B(1) of this regulation, except for coal mine waste impounding structures, shall be constructed to achieve a minimum static safety factor of 1.3 for a normal pool with steady state seepage saturation conditions.

Unless otherwise determined by the Department based on site specific conditions, impoundments meeting the criteria of §§A(1) and B(2) of this regulation shall be considered to meet a minimum static safety factor of 1.3 for a normal pool with steady state seepage condition, if the:

Soil Classification Chart.

An indication of sufficient moisture content in the fill material referenced in §B(3)(b) of this regulation is that the soil should form a ball which does not readily separate when kneaded by hand. The engineer may also specify other methods of testing moisture content.

Impoundments shall have adequate freeboard to resist overtopping by waves and by sudden increases in storage volume.

Impoundments meeting the Class (b) or (c) criteria for dams in “Earth Dams and Reservoirs”, TR-60 shall comply with the freeboard hydrograph criteria in “Minimum Emergency Spillway Hydrologic Criteria” table in TR-60.

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 contained in “Earth Dams and Reservoirs”, TR-60 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.

For impoundments not meeting the size or other criteria of 30 CFR §77.216(a), foundation investigation, as well as any necessary laboratory testing of foundation material, may be required to establish the stability of the foundation.

An impoundment shall include either a combination of principal and emergency spillways or a single spillway configured as specified in §D(2) of this regulation, designed and constructed to safely pass the applicable design precipitation event specified in §D(3) of this regulation.

The Department may approve a single open-channel spillway that is:

The required design precipitation event for impoundments meeting the spillway requirements of this section are:

Vegetative growth shall be cut where necessary to facilitate inspection and repair;

Ditches and spillways shall be cleaned;

Combustible material present on the surface, other than material like mulch or dry vegetation used for surface stability, shall be removed; and

Other appropriate maintenance procedures shall be followed.

A qualified professional engineer or other qualified specialist, under the direction of the professional engineer, shall inspect the impoundment. The professional engineer or specialist shall be experienced in the construction of impoundments. These inspections shall be made:

After each inspection required by §A(1) of this regulation, the professional engineer shall submit to the Department a certified report that the impoundment is being constructed in accordance with the approved plan and Regulation .08 of this chapter. A copy of each report shall be retained at or near the mine site.

Upon completion of construction, a certification statement and as-built drawing shall be submitted for each impoundment and impounding structure. The as-built drawing shall show the approved design and any modification or minor changes. The certification statement shall be signed and sealed by a professional engineer, and shall certify that:

The Department may require color photographs to be taken at the appropriate times specified in §A(1) of this regulation and submitted with the certification statement.

An impoundment shall be inspected at least annually by a professional engineer or other qualified specialist under the direction of the professional engineer until removal of the impoundment or release of the performance bond. The professional engineer or specialist shall be experienced in the construction of impoundments.

After each annual inspection, the professional engineer shall submit to the Department a certified report that the impoundment has been maintained in accordance with the approved plan and this chapter. The report shall include discussion of:

A copy of the report shall be retained at or near the mine site.

Impoundments meeting the Class (b) or (c) criteria for dams in “Earth Dams and Reservoirs”, TR-60 or the size or other criteria of 30 CFR §77.216 shall be examined in accordance with 30 CFR §77.216-3. Other impoundments not meeting the Class (b) or (c) criteria for dams in “Earth Dams and Reservoirs”, TR-60 or subject to 30 CFR §77.216 shall be examined at least quarterly by a qualified person for appearance of structural weakness and other hazardous conditions.

If an examination or inspection discloses that a potential hazard exists, the permittee shall immediately notify the Department of the hazard and of the emergency procedures formulated for public protection and remedial action. If adequate emergency procedures cannot be formulated or implemented, the Department shall be notified immediately. The Department shall then immediately notify the appropriate agencies that other emergency procedures are required to protect the public.

Size and configuration of the impoundment will be adequate for its intended purposes;

Quality of the 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;

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;

Water level will be sufficiently stable and capable of supporting the intended use;

Final grading will provide for adequate safety and access for proposed water users;

Impoundment will not result in diminution of the quality and quantity of water utilized by adjacent or surrounding landowners for agricultural, industrial, recreational, or domestic uses;

Impoundment will be suitable for the approved postmining land use; and

Vertical portion of any remaining highwall shall be located far enough below the low-water line along the full extent of the highwall to provide adequate safety and access for the proposed water users.