The Oriole Mine and associated waste coal existed alongside several reclaimed mine areas and consisted of an 87 acre barren, eroding, acidic stain on the otherwise green, stable, and productive broader landscape. The project reclaimed 42 acres of barren acidic refuse, 38 acres of slurry and outwash from the refuse piles, 7 acres of highly acidic impoundments, and 29.5 acres of borrow. The site was the Oriole Mine’s processing and load out facility used by other adjacent mines through the 1960’s. All operations had ceased and the tipple and railroad tracks were removed by the early 1970’s leaving behind the barren refuse piles, slurry, and acidic impoundments.
The site presented hazards to public health, safety, and welfare due to barren acidic refuse piles and impoundments. Sediment from the site collected in ditches around an existing private company’s office and shop adjacent to the site, forcing them to excavate the ditches to prevent drainage from the site inundating the shop area. During dry and windy periods the exposed refuse and fine slurry material were susceptible to wind erosion and accumulation onto equipment at the private business. Exposed iron sulfide minerals in the refuse materials oxidized producing secondary sulfate salts that created instant highly acidic and metal laden drainage during precipitation events that readily washed offsite. Further, the exposed refuse piles posed an open fire risk as the area is easily accessible by road, off road trail vehicle, and foot.
In 2012, the Kentucky Division of Abandoned Mine Lands (KYDAML) began to develop reclamation plans for the project site. Because the site was essentially an island in a sea of post-SMCRA mine land, the availability of cover material was a problem. The only available source of suitable material that did not risk the exposure of reclaimed refuse was in an adjacent permitted overburden disposal area. Fortunately, the area had passed its second phase of bond release and was owned by the major project area landowner, Alliance Coal. KYDAML was able to coordinate an agreement between Alliance Coal, KY Division of Mine Permits, KY Division of Surface Mine Reclamation and Enforcement, and the KY Department of Natural Resources Commissioner’s office to obtain the necessary increment revisions and early release of the necessary borrow area.
Natural stream channel design was implemented in the larger main drainage channels, down steep hillsides, and across the valleys whenever possible. This method was chosen to create more natural channels, minimize the risk of erosion of the channel materials, and to minimize the need for quarried rock to be brought to the site. The steeper slopes used a step-pool channel, while the flatter main drains were meandering channels. The channels were designed to slow the water flow path sufficiently to prevent erosion of the cover materials and to provide small pools within the channels for wildlife utilization. The bottom of the rock channels were lined with class II/III rock to prevent any head cutting. The banks of the channels were entirely composed of borrow material that was seeded and covered with erosion control blanket.
Appalachian Regional Reforestation Initiative (ARRI) has developed a forestry reclamation approach (FRA) that has been widely applied throughout Appalachia. The process involves end dumping material to achieve 4-6 feet deep coverage of uncompacted mine spoils in rows with central access roads crisscrossing the areas (Figure 10). These materials were not graded except for driving lanes every 100 feet (Figures 11). The site is lightly vegetated with a non-competitive seed mixture. Tree species are then selected and planted during the next available tree planting season (usually late Fall to early Spring). At the Oriole site the FRA overburden piles were created over an initial 2-foot of spoil material to allow the contractor to create a stable working base material.
A professional service planted 26,943 seedlings consisting of a mixture of hickory, oak, pine, redbud, locust and persimmon. KYDAML partnered with the Boy Scouts of America and Madisonville Community College to plant another 500 trees of the similar mix during the Oriole Mines Arbor Day event held on April 4, 2015. The volunteers also planted 160 (15th/16th variety) American Chestnut hybrid saplings provided by The American Chestnut Foundation. The volunteers were taught basic tree planting techniques and how the reclamation improves the land use while also reducing or eliminating the hazardous safety and environmental impacts from the site.
A 4 acre impoundment was treated, drained, lined with clean spoil, and filled with a wetland compost mixture to create a final treatment wetland. The wetland compost is a mixture of hay, straw, manure, and limestone sand blended onsite at the time of placement.
More than 485,000 cubic yards of acidic refuse and slurry were covered with non-acidic soil/ spoil material. The coarse refuse piles were graded to remove gullies while creating contour ditches and then covered with an average of 3 feet of spoil material. The slurry/coarse refuse outwash plains were covered with at least 2.5 feet of material and in most places these areas received 4 feet of material. The saturated slurry pumped and oozed under the weight of equipment as expected, so capping had to be done in stages and material was excavated as it crested in the open areas where the final ditches were to be constructed.
The large refuse pile in the center of the project was severely eroded with gullies greater than 6 feet deep. This material had formed alluvial outwash plains to the west and east of the pile. There were also minor mounds of mine spoil within the outwash plains. The gullies were so severe that grading was required. Because the grading exposed less weathered material, agriculture limestone was applied at the time of grading and again after grading so that it was incorporated into the Acid Forming Material (AFM) to neutralize the acid generated during weathering. Secondly, the graded material was capped with at least 2’ of heavily limed earthen cover minimizing contact with the atmosphere and thus reducing the AFM reactions. The grading helped in the establishment of drainage structures to minimize the overall erosion risk of the site.
The contractor graded the refuse materials and laid out ditches prior to cover material placement. Many of the ditches used a more natural stream channel design to create meanders and bends instead of straight rock channels. This included the creation of step-pool channels down steep slopes. On the western portion of the project site, the drainage tied into a constructed wetland that provides sediment retention, water quality improvements, and wildlife habitat. Wetland plant species were used to improve the water quality, increase retention time, and provide food sources for wildlife. On the eastern side, silt traps were used to collect sediment prior to the water being channeled into the existing ditches leaving the project site.