RECENT ISSUES IN WATER QUALITY MANAGEMENT AT WESTERN SURFACE COAL MINES1

• Jurisdiction: United States

Water Quality & Wetlands Regulation and Management in the Development of Natural Resources
(Jan 2002)
CHAPTER 9B
RECENT ISSUES IN WATER QUALITY MANAGEMENT AT WESTERN SURFACE COAL MINES¹
Joseph D. Friedlander ²
The Coteau Properties Company Freedom Mine
Beulah, North Dakota

Introduction

Water is a valuable commodity in America's West, making its management at surface coal mines even more important. Issues involving water treatment, monitoring and downstream impacts are unique at western coal mines. This paper addresses these water quality management issues, including design, construction and operation of sedimentation ponds, monitoring of water quality and regulatory agency oversight responsibilities. New federal rules, allowing reduced discharge monitoring and elimination of sedimentation ponds in some instances may provide Regulatory relief.

Design, Construction, Operation and Maintenance of Sedimentation Ponds

The quality of water discharged from surface coal mines is regulated pursuant to the Clean Water Act (CWA)³ and the Surface Mining Control and Reclamation Act (SMCRA).⁴ Through their implementing federal regulations⁵ these statutes overlap in their effect on mine operations. Both sets of regulations, and state counterparts in states having primacy, stress sediment control as the primary means of assuring clean water discharges from surface coal mines.

Most surface coal mines depend on sedimentation ponds to achieve water quality effluent standards. The concept behind sedimentation ponds is relatively simple. A pond receives sediment-laden runoff from a disturbed watershed stripped of topsoil or recently reclaimed land where topsoil has just been spread but has no erosion-controlling cover. After a period of time, usually a few hours to several days, the sediment settles from the water, and water meeting effluent standards can be discharged from the mine. Current EPA regulations for western surface coal mines include specific quantitative limits for total suspended solids, total settleable solids, pH and total iron in water discharges. States may place additional limits on water discharges.

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Design of Sedimentation Ponds

The United States Department of Interior Office of Surface Mining (OSM) has developed regulations prescribing design criteria for surface water management structures.⁶ Rules in the several states having primacy for regulating surface coal mining are at least as stringent as federal regulations, and may be more stringent. In addition, the size and configuration of a sedimentation pond may require compliance with a completely separate set of regulations developed by the Mine Safety and Health Administration,⁷ the United States Department of Agriculture Natural Resources Conservation Service,⁸ State and local water agencies and boards, and local planning and zoning rules.

Sedimentation ponds must:

Be prepared by, or under the direction of, and certified by a qualified, registered professional engineer, a professional geologist, or in any State which authorizes land surveyors to prepare and certify such plans, a qualified, registered, professional, land surveyor, with assistance from experts in related fields such as landscape architecture. 30 CFR § 780.25 .

Some coal mines do not have registered professional engineers or surveyors on staff and must contract out this work. Regulatory authorities will not approve ponds for construction until these professionals certify designs.

The proposed location of sedimentation ponds is extremely important. Obviously, ponds must be constructed in drainages or low areas below proposed mining disturbance. To minimize environmental disturbance, regulations require ponds be constructed as close as practicable to disturbed areas.⁹ This can be a point of contention between regulatory authorities and mine operators. This often boils down to differences of opinion between mine site professional engineers, trained and experienced in pond design and construction, and government regulatory agency staff who may have limited field experience, but nonetheless are charged with providing technical advice and approving design plans with the least environmental impact.

A complete field review conducted prior to preparing designs may reveal any special conditions not evident from topographic maps. Unexpected conditions that can have a significant effect on sedimentation ponds include:

• springs and seeps;

• unusually poor soils;

• near-surface groundwater levels

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• significant archaeological sites;

• old unrecorded cemeteries;

• water wells;

• buried gas, fuel, or water pipelines;

• buried or above-ground electrical and telephone lines;

• critical wildlife habitats;

• old underground mine workings¹⁰ ;

• farmsteads, including farm and ranch buildings, barns, storage bins, feedlots and corrals;

• built-up farm access roads or farmyard earthworks such as silage pits and grain bunkers;

• abandoned or active landfills or dumps; and

• old gravel pits.

Regulations leave little discretion regarding; minimum pond capacity. Ponds must be designed to contain or treat the runoff from the contributing watershed as a result of a 10-year/24-hour precipitation event, unless the mine operator can prove effluent standards can be met through some alternative means. This is the amount of precipitation expected, based on historical records, to occur over a 24-hour period once every ten years. This is highly site specific. For example, the l0-year/24-hour event at The Coteau Properties Company Freedom Mine near Beulah North Dakota is 3.12 inches, whereas the same design event at the Sabine Mining Company's South Hallsville Mine, near Longview, Texas

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is 7.25 inches. Sedimentation pond capacity is therefore dictated by expected inflows generated by a 10-year/24-hour precipitation event over an area the size of the contributing watershed.

Although minimum capacity will be approved by the regulatory agency, additional capacity should be considered to address contingencies such as management of excess groundwater, use of pond water for dust suppression, possible changes in watershed size during mining, and expected frequency of sediment removal. Although larger ponds require less frequent cleanout, their physical size and shape may make cleanout operations extremely burdensome and expensive, negating much of the savings.

Sedimentation ponds may or may not have constructed embankments, depending on topography. Great care must be taken in embankment design, to assure that quality embankment fill is readily available and that ground conditions are stable where the embankment will be constructed. This may require geotechnical studies and analyses of earthen corings before designs are prepared.

Spillways are located in sedimentation ponds where unusually heavy flows or excess runoff can safely pass through the pond and continue downstream without endangering the integrity of the embankment. These may be open channels or sized pipes placed into the embankment. In any event all spillways must meet additional regulatory design standards.

Sedimentation ponds must be designed with ease of construction, operation and maintenance in mind. This includes designed features such as valves, pump ramps, and spillways. Accessibility must be considered for ponds constructed in remote locations. If the same people responsible for pond design are also responsible for construction, operation and maintenance, they will have a vested interest in assuring a final design that can be most easily built, operated and maintained.

Prior to finalizing designs, all regulations from several agencies must be checked to make sure pond designs are in compliance. Although the agency regulating surface coal mining may approve the design, failure to review other regulations from other agencies (that may not even have review authority or responsibilities), may later result in costly delays in approval. At worst, it could result in issuance of notices of violation and expensive pond modifications in the field long after the pond is built.¹¹

Construction of Sedimentation Ponds

Following regulatory agency approval of sedimentation pond design, and assuming all other mining approvals have been received, pond construction can begin. A pond must be

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constructed before any other mining disturbance in the contributing watershed can occur.¹² Regulatory agencies are particularly sensitive to this requirement and pay close attention to the timing of pond construction as it precedes upstream disturbance. Once the receiving pond is constructed, the upstream contributing area is considered a "controlled watershed."

Although sedimentation ponds are constructed to control water runoff from disturbed areas upstream, surface water runoff from the pond construction site itself must also be controlled until the pond is completed. Depending on the size of the pond, a significant acreage may be disturbed at one time prior to embankment construction or excavation of the pond basin. It has been facetiously suggested to first build a sedimentation pond to control runoff from the sedimentation pond construction site, but first building a sedimentation pond below this ad infinitum.

Fortunately common sense prevails in this situation and the use of "best management practices" (BMPs) is normally approved by regulatory authorities during pond construction. BMPs include straw bale dikes, silt fences and sumps as temporary measures to control sediment in runoff from the pond site if storms occur during construction. Generally agencies enforcing SMCRA and CWA regulations have regulatory provisions and permit conditions which allow operators the flexibility to use these practices during this construction or transition phase and will wait until pond construction is complete before full enforcement of strict numeric effluent limits.

Because 1) BMPs are temporary...