RESEARCH IN ACID MINE DRAINAGE AND MINE LAND RECLAMATION

1997

Acid mine drainage pollutes about 5,000 miles of streams in the Appalachian region. Chemical treatment of AMD neutralizes acidity and removes metals, and the water must meet specific water quality criteria before it can be discharged to streams. There are various types of chemicals for neutralization but this technique of treating water is very expensive, and it must continue indefinitely. Ninety percent of AMD comes from abandoned coal mines (mostly deep mines) where no individual is responsible for treating the water with chemicals. Passive treatment systems, including the use of wetlands and anoxic limestone drains, offer an inexpensive alternative to treat many of these discharges without continual addition of chemicals and maintenance costs. Wetlands and anoxic limestone drains have been installed on more than 100 sites and water quality improvements have been demonstrated through monitoring of flows and acid concentrations in the water.

We have intensively monitored several passive AMD treatment systems in West Virginia. They treat flows ranging from 1 to 26 gpm and acidity concentrations from 170 to 2,400 mg/l. Five wetland systems reduce acidity by 3 to 76%, and iron concentrations by 62 to 80%. These wetlands are generally much smaller in area than that recommended by earlier formulas based on iron loads, but they still show good amelioration of acid and iron loads. In two of the five wetlands, limestone was not incorporated in the substrate. Iron and acid reductions were consistently greater in wetlands with limestone incorporated into the substrate. Eleven anoxic limestone drains (ALDs) reduce acidity by 11 to 100%. Based on our successes and failures in building and monitoring ALDs, the following conclusions have been reached: 1) organic matter should not be placed in drains owing to microorganism growth on the limestone, 2) the amount of limestone in the passive system shows little correlation to effectiveness and acidity reductions, 3) larger limestone particle size (1 to 6 inch) helped maintain water flow through the drain especially when some aluminum, iron, and grit accumulated in the drain, 4) oxygen intrusion into the drain reduced effectiveness, and 5) pipes installed in drains must be large in diameter with large perforations and to reduce the chance for plugging.

Jeff Skousen and Ben Faulkner

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Acid mine drainage (AMD) treatment can occur by passing the acidic water through underground beds of limestone. Under the right water flow and quality conditions, the water picks up alkalinity from limestone dissolution in these anoxic limestone drains causing neutralization of acidity and precipitation of metals from the water. Many anoxic limestone drains installed in the field have failed over time due to the metals in the AMD precipitating in the limestone drain, thereby clogging the limestone pores in the drain, which in turn reduces water flow and contact with limestone. Acid solutions containing ferric iron and aluminum were pumped through anoxic columns of limestone in a laboratory setting. Acid solutions containing only ferric iron were neutralized by the limestone for the first several hours of pumping causing effluents of neutral pH and low iron concentrations. Over the next 12 hours, neutralization of acidity by limestone continued but iron concentrations increased in the effluent to a equilibrium concentration. Acidic solutions containing aluminum reacted very similar. When sulfate was added to the acid water containing these metals, much greater metal precipitation occurred in the limestone columns. Based on this preliminary data, it appears that anoxic limestone drain effectiveness can be improved by increasing the ionic strength of the water entering the drain.

Pat Sterner and Jeff Skousen

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Coketon, West Virginia was a boom coal mining town and mining facility in the early 1900's. Millions of tons of coal were mined from underground and the coal was "cooked" in ovens to produce coke. The coke was shipped to mills where it smelted iron ore into steel. By 1920 the coke ovens were abandoned, and by 1960 all coal mining ceased. The unreclaimed lands and facilities in and around Coketon, as well as the poor quality drainage from the abandoned deep and surface mines, made this area eligible for reclamation through the Abandoned Mine Land Program. One of the greatest reclamation problems facing the mining industry is the control and treatment of acid mine drainage (AMD). AMD results from chemical and biological oxidation of iron sulfides (pyrites) common to many mining regions throughout the United States.

The biggest challenge to Coketon's reclamation was treating the large amount of AMD coming from one of the major deep mines in the area. The water flowed between 500 and 3,000 gpm, with a pH of 3.1 and acidity concentrations around 500 mg/l. Treating the AMD with chemicals would be a long-term and expensive option (about $100,000 per year for this water). The West Virginia Division of Environmental Protection contacted researchers at West Virginia University for help in designing a passive AMD treatment system, which does not require continual addition of chemicals and maintenance costs. Passive systems, such as constructed wetlands and anoxic limestone drains (ALD), have the potential to provide low-cost, low-maintenance treatment of moderate AMD flows. If AMD contains little dissolved oxygen and primarily ferrous iron, it can pass through limestone without armoring the rock surface. Wetlands underlain with limestone function in a manner similar to an ALD and extend ALD use to partially-aerated AMD by scavenging dissolved oxygen and promoting microbial reduction of ferric to ferrous iron. Due to the oxidation status of the Coketon water and the specific metal concentrations, a wetland or an ALD by themselves would not treat the water adequately. Therefore, the passive system designed for this site was an innovative combination of a wetland and an ALD. The innovative system was designed in two cells. The first cell had 5 ft of organic matter over 1 ft of limestone, while the second cell had 2 ft of organic matter over 6 ft of limestone. In total, the system is 2,600 ft long containing 19,000 tons of limestone and 4,800 cubic yards of organic material. The system was constructed on the site in the fall of 1993. Acid mine drainage was introduced into the system in July 1994.

The Coketon wetland/ALD successfully improved effluent water quality over a 12 month period. However, it is likely that this system is not functioning in an optimum manner. Poor substrate permeability in Cells I and II has led to significant overland flow, resulting in minimal treatment in the wetland portion and insufficient contact with the underlying limestone. It is likely that declining performance in this system is primarily attributable to hydrologic factors and not to clogging and coating of the limestone. This observation is consistent with continuously alkaline water from bottom samplers throughout the drain, continuing precipitation of iron in the system, and lack of ferrous iron in the effluent water.

Two small-scale replicas of the Coketon system were constructed in the WVU Plant Sciences Greenhouse, each measuring 38' x 2' x 3', and receive 50 gal of water per day. The AMD used in this experiment is significantly higher in dissolved oxygen, iron, aluminum, and acidity compared with the Coketon AMD. The greenhouse wetland/ALD functioned hydrologically as it was designed. Nearly 100% of the total influent aluminum was retained until June, 1995 compared with 17% retention in September, 1995. These data coupled with other measurements suggest that the greenhouse wetland/ALD increased alkalinity consistently until June while passing soluble metals to the precipitation pond. Following this time, limestone clogging or coating limited treatment efficiency. Passage of soluble iron was assisted by in vitro iron reduction activity.

John Cliff, Pat Sterner, Jeff Skousen and Alan Sexstone

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Abandoned coal mines cover about 200,000 acres in West Virginia. The Abandoned Mine Land Program has been reclaiming these areas for 18 years and only about 4 percent of the potential abandoned lands have been reclaimed. Remining allows an operator to remove remaining coal reserves that were left on the site and reclaim the entire abandoned mine site to current reclamation standards. Remining operations provide income through coal production, create jobs in the coal industry, and afford environmental enhancement through reclamation of previously-affected areas.

Acid mine drainage (AMD) from an Upper Freeport abandoned deep mine near Masontown was eliminated by surface remining the deep mine workings and adding alkaline overburden material during backfilling and reclamation. About 6,600 tons/ac of alkaline shale were hauled to the remined Upper Freeport site from a nearby Bakerstown surface mine, and the shale was placed on the pit floor and compacted around toxic material placed "high and dry" in the backfill. No AMD has come from the site during the past three years since reclamation. The cost of hauling the alkaline material to the site was about $4,000/ac. Chemical treatment costs of AMD previously coming from the site before remining ranged from $800 to $1,500 per year. The receiving stream is Mountain Run, a tributary of Bull Run of the Cheat River, and its quality has improved due to remining.

Two additional remining sites are being monitored during their respective remining and reclamation activities. Several point sources of AMD were located within the permit boundaries on both sites. On the Buffalo coal site, two acid discharges have been eliminated through mining and reclamation. Another significant source has not been encountered by mining yet. On the Albright site, reclaiming the refuse on the site with fly ash and covering with topsoil has reduced the acid discharges by 90%. These remining sites are in the Cheat River watershed, which is a major whitewater/tourism area in northern West Virginia. AMD from abandoned coal mines flows into these rivers decreasing their recreation value for fishing and whitewater activity.

Remining is the surface mining of previously-mined and abandoned surface and underground mines to obtain remaining coal reserves. Remining operations create jobs in the coal industry, produce coal from previously-disturbed areas, and improve aesthetics by backfilling and revegetating areas according to current reclamation standards. Remining operations also reduce safety and environmental hazards by sealing existing portals and removing abandoned facilities, enhance land use quality, and decrease pre-existing pollutional discharges. Ten sites in the Appalachian Coal Region were selected to 1) compare the costs associated with remining and reclaiming a site to current standards versus costs associated with reclaiming the site by abandoned mine land (AML) programs, and 2) evaluate water quality before and after remining. All of the remining operations in our study resulted in environmental benefits. Dangerous highwalls were eliminated, spoil piles were regraded, coal refuse left on the surface was buried, and sites were revegetated to provide productive post-remining land uses. In all but two cases, coal mined and sold from the remining operation produced a net profit for the mining company. While AML reclamation removes hazards and improves aesthetics on AML sites, remining these 10 sites saved the AML reclamation fund an estimated $4 million. Water quality after remining improved in all cases. Impediments to remining AML sites should be removed so that mining companies will actively select previously-disturbed and abandoned sites for remining and reclamation.

Jeff Skousen

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A pneumatic stowing device developed by Burnett Engineering, Inc. was used in West Virginia to seal a mine portal. The purpose of this project was threefold. First, it demonstrated an improved underground mine filling system and made the technology known to those who work to correct mine subsidence problems. Second, it sealed a hazardous mine from public access. Third, limestone filling of underground mines with acid mine drainage may be an effective method of reducing or eliminating acid discharges. The mine portal was pneumatically backfilled with 120 short tons of ASHTO number 57 limestone using the Burnett Pneumatic Pipefeeder for a distance of 70 ft and sealed. The portal was successfully sealed in less than four hours. The flow rate of water draining from the mine at the portal varied between 2 and 80 gpm. This flow rate remained unchanged during the first eight months after sealing and improved the water quality from a pH of 2.8 before the mine was sealed to a pH of 7.0. Acidity concentrations decreased from around 550 mg/L to net alkaline water during this same time period. Since January 1996, much higher flows caused much of the water to flow across the top of the limestone minimizing treatment.

Greens Run, a tributary of the Cheat River, is heavily polluted by acid mine drainage. Several point sources of acid water were located in the watershed. With the help of West Virginia University professors, Anker Energy designed and installed passive treatment systems to treat the acid drainage. The anoxic limestone drain was constructed in the fall of 1995 and water quality from the limestone drain has improved from a pH of 3.1 to 6.0, acidity concentrations have been reduced from 840 to 0 mg/l. More passive treatment systems are being planned for other tributaries of the Cheat River. Treating the water at their sources in Pringle, Heather, Lick, Morgan, and Greens Run, as well as Muddy Creek before the water reaches the Cheat is a cost-effective way of cleaning up the river for recreational, aesthetic and human uses.

In 1991, Pocahontas Land Corporation and West Virginia University started an experimental nursery on property near the high school in Welch, West Virginia. The five-year research project is demonstrating that plants such as trees, shrubs, vines, flowers, and fruits and vegetables can be grown on reclaimed minesoils. Aside from the research results, Mount View High School students have become involved. Flowers for the cheerleaders and for the prom have been grown on the nursery. The vocational/technical classes are building a concrete ornamental pool with fish and water liles. The biology class is also planning on growing fruits and vegetables to sell as a fundraiser. This project has had many positive benefits to the researchers, students, and citizens in Welch.

Another horticulture project is being initiated in Mingo County, West Virginia near Holden. A mining company has planted 5,000 grape plants and 250 trees on a mountain top surface mine. They have already constructed one greenhouse on the site and have plans to build several more. West Virginia University professors have helped the company in planting plans, plant species selection, and fertility requirements of the soil on the site for optimum plant growth. An aquaculture facility is also being designed with the help of WVU. The development of these income-producing opportunities may have a significant benefit to the citizens of these counties where unemployment is high.

Brad Bearce and Jeff Skousen

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Generation of electricity by coal-fired power plants produces large quantities of bottom ash and fly ash. New power plants commonly use fluidized bed combustion (FBC) boilers, which create ashes with high neutralization potential (NP). These ashes, due to their alkaline nature, are often used in surface mine reclamation to neutralize acidity and reduce hydraulic conductivity (Ksat) of disturbed overburdens. Conventional fly ashes from older power plants exhibit a range of pH and NP, with some ashes having neutral or acidic pH and low NP values. Some of this fly ash and FBC ash are being used in reclaiming surface coal mines by applying the material to the coal pavement and by mixing the ash with acid-producing overburden materials. In this setting, the alkalinity of the ash is being used to offset or neutralize the acidity generated by pyrite oxidation in the overburden and pavement. In addition to the excess alkalinity contained in them, fly and FBC ash are enriched with many trace elements, particularly metals, which may be leached into nearby water sources. Some FBC ashes, due to their calcium oxide content, harden upon wetting and cause the ash to set up like concrete. A strategy for controlling acid mine drainage on surface mines is isolating and segregating acid-producing materials with a barrier to limit its exposure to air and water. FBC ash could be used as a alkaline barrier material, but its metal content and hardening may cause problems. To maximize alkalinity release from FBC ash, the material should be mixed with a porous material (like conventional bottom or fly ash) to minimize hardening into a mass and allow continual release of alkalinity for longer time periods. We measured the hydraulic conductivities (Ksat) of various mixtures of a low NP fly ash and FBC ash and also determined the release of alkalinity and metals over time from these mixtures by leaching with a 0.01M sulfuric acid solution and acid mine drainage (AMD) from a Pittsburgh coal deep mine.

Results indicate that water flowed through these materials at a moderate to moderately high rate. If these materials become saturated in the field, it appears that they may swell, reducing the total porosity. This swelling may reduce the Ksat from that which was determined in the laboratory. Mechanical compaction or overburden compression may also reduce the Ksat. However, swelling and/or compaction will probably not reduce the Ksat to much lower than 10-5 or 10-6 cm/sec.

A number of trace elements were observed in the leachates from coal ash mixtures using sulfuric acid and some of those elements exceeded drinking water standards. Arsenic was found in high concentrations in the leachates from the conventional low NP fly ash. We also observed that concentrations of arsenic in the leachates can be controlled by developing proper ash mixtures having suitable NP so arsenic is not released. Selenium, on the other hand, often exceeded drinking water standards. Unlike arsenic and other trace elements, selenium in ash is not controlled by a precipitation reaction. Thus various combinations of ash had very little effect on selenium concentrations in leachate samples. Manganese was released from the low NP fly ash at a constant level, while the FBC ashes did not release manganese. Mixing FBC ash with low NP fly ash reduced the amount of manganese in leachates, however after 60 pore volumes of leachate one of the FBC ashes released manganese.

Leaching these ashes and mixtures with acid mine drainage (AMD) caused the arsenic and selenium concentrations in leachates, which were released with sulfuric acid leaching, to decrease. Leaching with AMD caused the iron and aluminum inherent in AMD to complex arsenic and selenium and make them unavailable for leaching. Lead, cadmium, and barium concentrations in fly ash leachates were not high enough to cause water pollution problems with either leaching solution. For both leaching solutions, manganese was released from low NP ash at a constant level, while FBC ashes did not release manganese or released small amounts only after the alkalinity in the ash was completely exhausted by acid leaching (after 60 pore volumes).

Jeff Skousen, DK Bhumbla and John Sencindiver

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Acid mine drainage (AMD) is often associated with coal and metal mining, and expensive chemical treatment of AMD may be required before discharging into receiving streams. Much attention has been devoted to developing inexpensive, limestone-based systems for treating AMD with little or no maintenance. A major problem with using limestone in AMD treatment is coating with metal hydroxides and gypsum when exposed to AMD, a process known as "armoring". It is generally assumed that once armored, limestone ceases to neutralize acid. Another problem is that precipitates fill limestone void spaces, resulting in reduced contact with water. High flow rates of water through the limestone bed may be able to flush the precipitates and minimize plugging, although armoring occurs regardless of water velocity. Laboratory and field experiments investigated the influence of armoring on limestone solubility and the implications of armoring and plugging on the construction of open limestone channels for treating AMD. In two laboratory studies, hydrochloric acid solutions or AMD were treated with armored and unarmored limestone. Results of the first laboratory study indicated armored limestone was 50 to 95% as effective in neutralizing a hydrochloric acid solution as unarmored limestone. The second laboratory study showed that armored limestone was only 9% less effective in neutralizing AMD as unarmored limestone. The field study surveyed 2- to 8-year-old, rock-lined channels constructed for erosion control. One channel was constructed of sandstone and seven others were constructed of limestone. Open limestone channels, though armored, reduced more acidity in AMD (4 to 62%) than the sandstone channel (2%). The results from open limestone channels were compared to an acid neutralization kinetics model that predicts the rate of acid neutralization based on dimensions of open limestone channels for a specific AMD flow and acidity. The open limestone channels in the field neutralized more acidity than the model predicted. The primary application of open limestone channels (like other passive treatment systems) is for watershed restoration projects and abandoned mine land reclamation projects where one-time installation costs are incurred, little to no maintenance is required for treatment, and the system does not have to produce effluent-limit quality water.

Paul Ziemkiewicz, Jeff Skousen, Dave Brant and Pat Sterner

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The northern routing of Appalachian Corridor H, a highway connecting Alkenes, West Virginia to Strasburg, Virginia, will transect the Blackwater River watershed near Davis, Tucker County, West Virginia. Much of the watershed is located in an extremely scenic and popular tourist area, which has a great impact on the social and economic structure of the area. This watershed is also heavily impacted by abandoned mine lands (lands that were mined and not reclaimed prior to 1977), detracting from the tourism-based economy of the region. This study developed methods for improving and protecting water quality in the Blackwater River watershed and also applied techniques for reclaiming abandoned mine lands during construction of Corridor H. Remote sensing and ground surveys located and characterized wetlands and abandoned mine lands in the watershed. Water quality in streams were also determined. Based on the locations of abandoned lands and poor quality wetlands, recommendations will be made for replacement of low quality wetlands with biologically functional wetlands in high profile areas. Because many of the existing wetlands are of low quality and closely associated with unreclaimed mine lands in the watershed, environmental gains will be achieved during highway construction by using mitigation acreage from low quality wetlands to construct wetlands for treating acid mine drainage. Small changes in routing will be recommended to maximize use of abandoned mine lands for highway fill material and reclaimed as part of the highway construction process.

Jeff Skousen, Alan Sexstone and Paul Ziemkiewicz (Ben Stout, Wheeling Jesuit College, PI).

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Chopped newspaper (CNP) and sewage sludge (SS) are two significant waste streams that consume substantial landfill volume annually. When mixed with SS, CNP increases the solids content and may also reduce mineral N losses from decomposing SS. The effects of application of CNP/SS amendments on N mineralization and uptake in a mixed grass-legume pasture were investigated on a Guernsey silt loam (fine-loamy, mixed, mesic Aquic Hapludalf) soil. In both a laboratory incubation and a field trial, CNP was mixed with SS to produce C:N ratios of 6:1, 12:1, 24:1, 36:1 and 60:1. In the 32-week incubation study, 16% of the N from SS was mineralized, net N mineralized was not different among CNP-amended treatments, and mineralized N was retained by absorption in CNP. In the field study, addition of SS alone (6:1) and with a low rate of CNP (12:1) resulted in significantly greater forage yields than the unamended control or higher C:N ratio amendments during the first year. Low forage yields for high C:N ratio amendments were attributed to low available nitrate-N and shading. Forage yields among treatments during the second year were not different. A CNP to SS ration of about 2.5 to 1 is recommended because this ratio created a semi-solid product, which can be spread with standard farm equipment. At this ratio, yields and soil nitrate-N were only slightly depressed compared to SS alone in the first year, but were not different during the second year.

Robert Bricker and Jeff Skousen

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