Reclaiming Coal-Mining Sites: Challenges in Erosion Control

July 1, 2001
Reclamation of coal-mining sites demands special consideration of challenging environments, particularly in mountainous areas. Reclamation specialists, whether mining company employees, independent contractors, or representatives of regulatory agencies, have developed innovative approaches to returning mining sites into productive habitat. Regulatory distinctions divide coal-mining sites into two reclamation categories: abandoned mine land (AML), those sites mined prior to implementation of the federal Surface Mining Control and Reclamation Act of 1977, and sites mined since then, whose reclamation measures are supervised directly by mining companies. Mine site reclamation typically includes site preparation, initial revegetation, specific erosion control measures, and often specialized planting efforts to create desired land uses. The Peaks and Valleys of HydroseedingCharles Massie, president of Massie Reclamation in Bradley, WV, has worked on mine site reclamation, particularly on AML sites, since such work began in the early 1980s. His company specializes in planting and erosion control on commercial and highway sites as well as mining areas. Massie carries out mine land reclamation primarily in southern West Virginia, through both private contracts with coal companies and government projects awarded through public bid. The reclamation sites range broadly in size: Deep mine sites are usually only 2-4 ac., whereas surface mining sites range from 20 to 1,200 ac.Planned postmining uses of the coal-mining sites Massie works to reclaim include pastureland, woodland and wildlife areas, and more recently commercial forests. Massie explains how revegetation differs for these uses: “On the pastureland, of course you would put primarily forage grasses back on the site. [For] woodland or wildlife areas, you would plant species that are more prone to wildlife habitat, such as a food source or cover, berry-producing species, or nut-producing trees. On the commercial end, you would need to plant conifers, pine, or hardwoods, such as oaks.” The commercial forests present particular problems in establishing initial vegetation. “If you have a dense vegetative cover of grasses and legumes, it’s hard to get the small tree seedlings to survive.” Massie has participated in “experimental” plantings of low-growing grasses and legumes and in planting grasses less densely. “We try to find the medium where we can control siltation and erosion but not choke out the trees.” Massie’s choice of seed varies by site, but he and his crew generally use a mixture of 15% legumes and 85% grasses. When planting for pastureland, they apply 100 lb. of seed mixture per acre, with seven or eight different seed varieties. For commercial forestry, Massie cuts the number of species back to about four, and he lowers the seeding rate to around 40 lb./ac. “to get the competition factor.” Most site permits require native species to be planted, particularly native trees. Native grasses used include orchard grasses, timothy, and clover. Massie explains that non-native species are chosen more often for postmining wildlife habitat “to give more diverse food sources.”At active mining sites, coal companies regrade the area before contracting reclamation work. In contour mining such as that in mountainous West Virginia, moving an entire mountaintop might be part of the specified permit. Upon completion of mining, Massie explains, “[Coal companies] go back in and reconfigure, or they backfill if it’s a contour mine, and they smooth it up and leave the dozer tracks to catch the seed on the slope. That is the seedbed preparation.” Subsoil is more commonly applied than topsoil to sites because there simply isn’t much topsoil on the rocky areas.The site permit holders are required to perform soil testing, then Massie’s group takes additional soil samples, primarily to determine soil acidity and corresponding fertilizer requirements. Massie and his crew do not move earth, but once the ground is prepared, hydroseeding is their first step. The very rugged terrain of the West Virginia mining sites absolutely requires hydroseeding for revegetation to be successful. “Access is a problem,” admits Massie. “They can’t cut a road everywhere you need to go to spray this material, and it’s too steep to do it with farm equipment. A lot of the area is so steep the bulldozers have trouble.” The company employs seven Finn 3,300-gal. HydroSeeders, and each truck carries 800 ft. of hose that can be hooked up and connected. Massie explains that pumping pressure cannot easily overcome such distances on steep upslope areas. “But over a big valley fill, we have had 2,200 feet of hose out. That’s half a mile–now that’s an access problem!” Mud can also restrict access, particularly during wet winter seasons. Soil amendments in Massie’s hydroseeding mix include fiber mulch, lime, and 10-20-10 fertilizer, which is usually applied at a permit-specified rate of 600 lb./ac. Because of the very low fertility of the coal overburden at these sites, Massie almost always finds it necessary to exceed permit minimum requirements for fertilizer. Fiber mulches range from paper pulp to wood fibers. On some jobs, Massie applies straw mulch that is blown after seed and soil amendments have been applied, then he follows it with a powdered tackifier that is mixed with liquid and squirted onto the straw to hold it down. Most of Massie’s mine reclamation sites do not demand tackifiers; only those identified as critical areas or potential problem areas do.Occasionally Massie’s AML jobs require particular erosion control measures, such as staking in hay bales along slopes to deter and slow water flow and to catch silt behind the bales. Site permit holders are cited if muddy water is discharged from the site. Additional erosion control measures that Massie employs on small problem areas include Curlex blankets, which are wood shavings sandwiched in plastic mesh, straw blankets, coir mat, jute, and more recently polypropylene. Blankets and other materials are used on very rocky areas, particularly in ditches or channel areas, to prevent water from cutting deeper paths. Massie notes that, because the polypropylene takes longer to biodegrade, “it’s more stable and will last longer, especially in a high water—velocity [site].”Massie’s mine reclamation work is, not surprisingly, seasonal, but as long as outside temperatures remain above freezing, hydroseeding can be carried out during winter months. Frost heaving of the ground actually allows the seed to embed farther, where it belongs, and the seed lies dormant until the weather breaks in March or April. Late fall tends to be an off season, as seed applied then might actually begin to grow before a freeze occurs, and the summer months are typically too hot and dry for hydroseeding. Time required for site establishment depends on the planned postmining use: Pastureland can be ready the season following planting, but on woodlands, three-year-old trees must be present for permits to be released. Massie explains that coal companies are not granted permit release until at least five years after the last seeding is completed, even for pastureland.
Award-Winning Reclamation in the Deep SouthHydroseeding at West Virginia coal-mine siteThe federal Office of Surface Mining (OSM), part of the US Department of the Interior, provides oversight for all mining and reclamation activity supervised by state agencies. Each year, the OSM recognizes “Excellence in Surface Mining Reclamation,” and Alabama’s Drummond Coal Company received this distinction in 2000 for reclamation activity on its Arkadelphia mine site, a surface mining operation about 50 mi. northwest of Birmingham. Mining at the site began in the mid-1960s, and extraction of reserves available through surface mining was completed in 1995. Dwight Hicks, manager of permitting and regulatory compliance at Drummond, describes the premium-grade Arkadelphia reserves as “a single seam [that was] a nominal 18 inches thick and covered largely by 60 to 70 feet of hard sandstone.” The pre-mine uses of the Arkadelphia mine site were pasturage, grazing land, hay land, and some agriculture. Drummond decided to remove the good-quality topsoil on the site, stockpile it, and replace it after grading at the site was completed. Topsoil stockpiling and replacement are now regulated by federal reclamation law, but Drummond was charting new waters with this program at Arkadelphia in the mid-1970s. “Our reclamation plan called for removal and replacement of a minimum of 1 foot of soil material,” says Hicks. Any trees on the site at the time of initial disturbance were windrowed at the bottom of slopes to help control erosion. Drummond implemented an innovative “stairstep” approach to coordinating mining and reclamation efforts. Initially topsoil was stockpiled as it was removed, but once mining was completed at a portion of the site, that area was immediately graded and the topsoil replaced, while mining continued elsewhere along the coal seam. The approach proved both cost-effective and time-effective for Drummond. “As soon as we could get grading finished, put down topsoil, [and] establish drainage control, we could get vegetation established more quickly,” explains Hicks. “That’s when we would start our bond liability period. It was a rather coordinated set of events–highly orchestrated, efficient, and effective.”Early in the reclamation effort at Arkadelphia, Drummond established a cropping system on reclaimed acres to harvest viable seed for further revegetation. Drummond contracted with an independent farmer to produce the seed for the company, primarily Sericea lespedeza, an aggressive legume species. The seed was returned to the reclamation seed blend used on the next segment at Arkadelphia or was included in blends for Drummond’s other mines. In the 20 years that Drummond has maintained the seed production program, Hicks estimates that it “harvested, reclaimed, and reutilized” several hundred thousands of pounds of clean seed. Revegetation takes place at Arkadelphia during two seasons, March to June and September to late November or early December. Drummond has developed specific reclamation seed blends: cool-season and warm-season blends and special high- and low-pH blends, as soil conditions demand. Sericea lespedeza is included in all reclamation blends. “It’s a long-term legume,” explains Hicks. “It’s a soil builder and it has a deep root system, so it has the staying power to see us through that five years or more of bond liability.” Drummond’s warm-season seed blends include extensive Bermuda grass and Pensacola Bahia grass and, for quick cover and erosion control, a species such as browntop millet. Kentucky 31 fescue is a common grass in cool-season blends. Revegetation blends are normally applied at a rate of 100 lb./ac. and include a minimum of five different legumes and grasses. In addition to Sericea lespedeza, common legumes include clovers–particularly crimson clover–and alfalfa varieties. Warm-season seed is scarified, or hulled, so that it breaks dormancy very quickly. Hydroseeding at Arkadelphia was primarily employed on smaller acreages, as the accessible terrain on the site allowed for the use of conventional farming equipment.With revegetation, Drummond applies a balanced fertilizer such as Triple 13, at a usual rate of 700 lb./ac. Because Alabama topsoils are acidic, reclaimed topsoil typically receives agricultural lime applications of 3-5 tons/ac. On very acidic areas, Drummond has applied as much as 25-30 tons of agricultural lime per acre.Revegetation at Arkadelphia was considered the primary means of establishing erosion control. “Once we would put topsoil on the big acreage–the flatter areas–erosion control would come through quick establishment of vegetation: seeding, fertilizing, and lime application,” Hicks explains. “Then we would come back in and put hay mulch on top of everything.” Hay is applied at a rate of 4,000-4,500 lb./ac. Additional erosion control measures were sometimes needed at Arkadelphia. “Because we were replacing topsoil on graded overburden, on somewhat rolling terrain,” says Hicks, “we had to develop a strong erosion control set of practices and guidelines.” Diversions and terraces were heavily implemented on slopes, including many riprapped and rocked downdrains. Sediment ponds were another control measure. “We had a very extensive set of sediment ponds that would be put in for our point-source outfalls: If we had any sediment coming off a site, it would be captured before it would go to any receiving stream.” Sediment ponds are designed to retain water long enough to allow solids in the water to settle out. Erosion control measures were taken on the site simultaneously with seeding, with terraces, diversions, berms, and channels revegetated along with the rest of the area being seeded.Hicks considers maintaining water quality according to extensive water-quality regulations to be one of the largest challenges of mining reclamation. “That’s one of the reasons you have to have good erosion control. You must have a good vegetation program, to get these areas stabilized and get a vegetative cover back over them as quickly as possible. That is the main way you maintain water quality.” Drought conditions can prove devastating to revegetation, although Hicks believes that drought stress can be overcome somewhat by implementing quality reclamation and vegetation measures initially. “That’s where, for us, the application of hay mulch is so critical. That not only helps control erosion, it also helps hold moisture; it cuts down on moisture depletion until you get vegetation established.”As the first land to be reclaimed on the Arkadelphia site began to mature, Drummond looked beyond seed production to commercial forestry. “We replanted trees–loblolly pines–for commercial use,” explains Hicks, noting that effective timber production was a prime consideration for the OSM award Drummond received in 2000. The timber is managed directly by the coal company. Some small forested areas have been sold, including a site that has been turned into a golf course. Another postmining use on the mine site is primarily industrial, a quarry operation that leases the property from Drummond. Sandstone rock that was part of the overburden material is sold commercially for aggregate used in road construction. The postmining land uses at the reclaimed areas of the Arkadelphia mine site thus range from industrial/commercial to pastureland for cattle, commercial timber land, and recreational use.Hicks emphasizes the importance of carrying out effective reclamation and establishing long-term erosion control, in terms of both environmental standards and corporate benefit. “We have stringent standards that we have to meet; it’s important environmentally. On the other hand, since we have this responsibility for bonding and reclamation, we have all that money–for Drummond, millions of dollars–that can be outstanding in bond liability at any period of time. It behooves us to put together a program that’s going to control erosion, reestablish vegetation, and get through our bond liability period as quickly as possible, so that bond money can be applied to other operations.”A Regulatory Point of ViewWest Virginia coal-mine siteRichard Davis is a reclamation inspector with the Virginia Department of Mines, Minerals, and Energy (DMME), in the Division of Mined Land Reclamation. The division’s four units are responsible for enforcing coal-mining reclamation regulations and for reclaiming AML. Davis initiates AML reclamation projects, inspects existing projects, and manages an inventory of AML properties throughout Virginia. The AML reclamation program is funded nationwide through grants from the OSM, with funds derived through fees collected on coal production in active mines. Davis explains that the actual reclamation work is performed by contractors who earn the jobs through competitive bids and that he works directly with these contractors. Coal mining in Virginia takes place almost exclusively in the southwest corner of the state, in rugged habitats similar to those found in southern West Virginia. AML project sites handled by the Division of Mined Land Reclamation have been as small as 100 ft.2–a former deep-mine portal in a front yard–and as large as 30-40 ac. on a surface-mined area. AML projects in Virginia generally seek to create postmining land uses of unmanaged forest or hay-land pasture, according to the wishes of the landowner. The AML unit maintains standard specifications for seed mixes depending on the intended land use. For example, on a project with a postmining land use of unmanaged forest, Davis says they’re using grasses and legumes that aren’t particularly aggressive in their growth habitat. He explains that such varieties are more complementary to tree species. Timing of tree planting is also considered critical. “On an abandoned mine land project, we try to get the trees out just as soon as we can after hydroseeding.” Doing so helps with erosion control and tree establishment and finishes up contracts on the site sooner. Trees chosen for unmanaged forest sites–including northern red oaks, white pines, sawtooth oaks, Chinese chestnuts, and black locusts–are often selected for their benefit to wildlife species. Revegetation contractors on AML are required to inoculate legume seeds with bacteria so the legumes can incorporate the bacteria and begin the process of nitrogen fixation. “The soils we normally have on the surface might not have the native bacteria,” says Davis. To further enhance nitrogen fixation and improve other soil properties, the AML section is starting to use mycorrhizal tree seedlings, which should be better suited for these harsh environments. Davis explains that “the mycorrhizal seedling has a fungus component at the root, [so] it is much better able to absorb water and nutrients” than are other seedlings.Davis’ group is encouraged by other state and federal agencies to use native species on AML sites. The AML unit is entering into a research project with the Powell River Project–a cooperative program run by Virginia Tech, industries in southwestern Virginia, and other organizations serving the Virginia coal-mining region–to investigate establishing native, warm-season grasses on such areas. The emphasis of such an approach is to encourage natural ecological succession. “Species that we are using now might be a mix of native and non-native species, but these are nonaggressive species,” explains Davis. “Over the past year or so we have gotten away from using species that are very aggressive, like Kentucky 31 fescue, Sericea lespedeza, and crown vetch, because they tend to inhibit ecological succession.” The AML sites in southwest Virginia are very steep, with low-pH, low-fertility soils. “The topsoil has long since been buried or washed away,” Davis explains. “Often there is very little soil material there at all and lots of unweathered rock.” Using soil amendments to create a suitable topsoil substitute is more common than bringing in topsoil. After the soil has been tested, lime is applied to raise soil pH to around 5.5. The soil is further amended with fertilizer, usually 16-27-14, typically applied at 500 lb./ac. When a contractor chooses to hydroseed, such as on steep slopes, lime is applied in the mix, but Davis’ group encourages contractors to spread lime separately where possible and incorporate it into the soil. Contractors use whatever hydroseeding equipment they prefer. Often the primary contractor will subcontract out the revegetation aspect of reclamation. Site preparation involves grading–running track equipment such as bulldozers over the site–according to specifications of the reclamation plan. As in West Virginia, site access can be a problem, and hydroseeding contractors might need to hook up lengths of hose to reach their sites. As at Drummond’s Arkadelphia mine, Davis and the DMME rely heavily on revegetation for erosion control on AML sites. “Sometimes this calls for contractors to do a temporary seeding,” Davis explains. “We would use an annual species, something that’s going to grow and produce some cover very quickly. Then we would follow up with our permanent seeding.” Sediment control structures sometimes installed at AML sites include hay bales, straw-bale barriers, and silt or sediment fences. Rock check dams constructed at some sites impound small amounts of water for a very short time, allowing the water to drain through while slowing it down enough for particles to drop out. Silt fences, constructed of porous fabric, accomplish the same function. All of these structures are removed from a site prior to release of a reclamation contract. When AML sites are particularly difficult to revegetate, Davis’ group applies excelsior netting: The excelsior, which is left down permanently, consists of small wood fibers encased in a mesh netting that photodegrades.Davis describes the DMME’s particular concern with controlling runoff from AML sites: “A lot of our coal fields in southwest Virginia drain into the Clinch River and the Powell River, [where] there are numerous endangered species, mostly freshwater mussels. The US Fish and Wildlife Service has designated these areas as critical habitats, so we’re especially concerned with controlling erosion of our abandoned mine lands.” Davis is enthusiastic about a trend in Virginia’s AML reclamation that involves wetland areas. “Whenever we have a project around a wetland, we tailor our seed mix to the wetland areas, rather than use our upland seed mix.” Reclamation is believed to be enhanced by wetland development because, according to Davis, “Wetlands provide habitat for lots of wildlife species, they serve to clean the water, [and they] absorb water and release it over a longer period of time, so they sort of act as flood control.” Developing WetlandsThe importance of wetlands to AML sites has also been a focus of the Powell River Project. Directed by Carl Zipper of Virginia Tech, the Powell River Project’s mission is to carry out research and education programs that facilitate mine land reclamation and benefit both businesses and communities in Virginia’s coal-mining regions. Rob Atkinson, associate professor of biology, chemistry, and environmental science at Christopher Newport University in Newport News, VA, has devoted a great deal of research effort, through the Powell River Project, to determining the benefits of wetlands on surface-mined land. On many surface-mined sites in southwest Virginia, small depressions, formed when landscapes were altered by mining, have over the years developed characteristics of wetlands. Atkinson has evaluated many of these depressions on AML sites. He not only shares a belief in the benefits of these wetland areas, citing evidence of the many ecological services they provide, but he also advocates deliberately constructing small wetlands on AML sites to provide these beneficial functions. Constructed wetlands could assist in erosion control, trapping sediment and preventing runoff, and unlike sediment ponds, the wetlands would not be removed upon completion of permitted reclamation. Atkinson explains that the wetlands could be constructed during site preparation and grading and that hydroseeding or other revegetation could take place as they normally would. “If you have a 100-acre site, you would probably end up with an acre of wetland. You would hydroseed the whole 100 acres.” He explains that wetland areas enhance the diversity of vegetation that develops. “You have an ecological battle going on between upland plants and wetland plants. You get zonation in response to that. You get various zones within the wetlands and various zones adjacent to the wetlands, and that’s good for wildlife.” Atkinson admits that coal companies and landowners are wary of the potential problems associated with wetland construction, including liability associated with risks such as accidental drowning, and potential regulatory restrictions on the wetlands, as required by the Clean Water Act. He promotes developing very shallow wetlands, to avoid risks as well as to mimic such natural wetland areas as beaver ponds, and believes that keeping the wetlands very small might eliminate them from inclusion under wetlands regulations.A Different ApproachAn unusual approach to mine land restoration is being explored by the Bureau of Land Management (BLM) in northeast Oregon. BLM and the Oregon Department of Geology and Mineral Industries are experimenting with using cattle to improve soil quality on the site of an abandoned gold mine near Baker City. Cattle are fed in small, fenced lots, and feed, wastes, and native seed are incorporated into the soil through “hoof action.” Increased organic material and microbial activity should enhance revegetation efforts. After two years of monitoring soil structure, vegetative species diversity, cover, and invasion of noxious weeds, BLM Surface Protection Specialist Kata Bulinski says that site restoration has benefited from what she and her coworkers call the “cowmpost” treatment.ConclusionThe variety of approaches to mine site reclamation described in this article range from the tried and true to the cutting edge. All have their place as managers, reclamation contractors, and scientists balance environmental regulations, business considerations, and scientific innovation to create solutions to individual reclamation challenges.