No abstract

Passive treatment system components containing limestone are an effective means to decrease Mn concentrations in coal mine drainage. As precipitates, sediment, vegetation, and other materials accumulate in the void spaces, permeability decreases and treatment effectiveness is reduced. Recently, the ability to recover manganese-bearing material for potential economic use while restoring treatment efficiency has been demonstrated at the De Sale Phase 2 passive treatment system, installed at an abandoned surface coal mine in western Pennsylvania. Efforts to date include pre-and post-recovery water monitoring; development of a unique "full-scale" recovery technique; preliminary physical, chemical, and mineralogical analysis; and identification of a potentially economically-viable use of the recovered material. The horizontal flow limestone bed was monitored 3, 24, 64, and 118 days after Mn recovery. Comparing the influent with the effluent indicated decreases in dissolved Mn concentrations from 64 to 30 mg/L, 55 to 10 mg/L, 46 to 9 mg/L, and 20 to 8 mg/L, respectively, essentially doubling treatment effectiveness. Over 40 cubic yards (30 cubic meters) of manganese-bearing material were recovered. Currently, the Mn material is being used by local ceramic artists as a glaze colorant and is being evaluated by other industries including brick manufacturing.

On 01/25/05, a 10,000-gpm "blowout" of the century-old Nickle Plate Mine (Pittsburgh coalbed) occurred in a public sidewalk about 12 miles southwest of downtown Pittsburgh, PA. The US Office of Surface Mining, first responder, installed diesel pumps and drain lines along public streets to control and convey the discharge to a nearby stream. On 02/22/05, the Pennsylvania Department of Environmental Protection, Bureau of Abandoned Mine Reclamation issued a 90-day emergency contract to Environmentally Innovative Solutions, LLC to provide a permanent control. With numerous partners (federal, state, local agencies; local residents and businesses), property access, stream and mine pool water quality data, historical mine mapping, and other pertinent site information were acquired. Nine options were developed and evaluated. Paramount in design considerations was public health and safety followed by effectiveness, reliability, community and environmental impact, long-term maintenance requirements, installation cost, and aiding future work including grouting to address mine subsidence issues and treatment of the abandoned mine drainage. Piezometers and test pits were installed in city streets, private driveways, and on undeveloped property and mine pool response tests were conducted. After data evaluation, the mine pool was manipulated to discharge about ½-mile northeast of the "blowout" on undeveloped land to an AMD-degraded receiving stream. By 05/20/05, a primary gravity drain, a secondary drain, and an early warning system at the "blowout" had been completed. Subsequent monitoring confirms the facilities are functioning as designed.

Gypsum (CaSO 4. 2H 2 O) precipitates were observed in limestone beds at four vertical flow ponds (VFP) treating acid mine drainage, but the textures and localization show that it precipitated within other materials, not in contact with the open solution. At the Filson 1 VFP, gypsum was found within clay and organic matter left as residues on the surface of partly dissolved fragments of impure limestone. It was also found in the contact zones between fragments. At the Tangascootack 1 VFP, gypsum coated limestone and was overlain by amorphous Al precipitate. At the Jennings VFP, gypsum was present in limestone-bearing compost and within Al-rich gel occupying pores in limestone gravel. At Middle Branch, Kettle Creek, gypsum occurred in Al-rich gel and on limestone. At all sites, the effluent water was undersaturated with gypsum. Gypsum at these sites is interpreted to have formed in situations where limestone dissolution was characterized by diffusive transport of Ca away from the limestone surface. In this situation, the Ca concentration near the limestone surface is considerably higher than in the open solution, so that gypsum was oversaturated and precipitates, even though the open solution was undersaturated. The occurrence of gypsum as coatings or as a component of an impurity layer probably slows the dissolution of limestone, and makes the VFP less effective in neutralizing acidity.

Abstract. Abandoned mine drainage is a major source of water pollution in Pennsylvania, West Virginia, and other historical mining districts. Technology which utilizes no harsh chemicals and no electricity, and requires minimal maintenance known as passive treatment is being developed to address this pollution problem in a relatively cost-effective manner.