The hydrologic and water quality characteristics of a partially flooded, abandoned underground coal mine near Latrobe, PA, were studied to suppo1t the development of techniques for in situ abatement of its acidic discharge. A quantitative understanding of the conditions affecting discharge flow was considered to be very important in this regard. Statistical analysis ofhydrologic data collected at the site shows that the flow rate of the main discharge (a borehole that penetrates the mine workings just behind a set of pmtal seals) is a linear function of the height of the mine pool above the borehole outlet. Seepage through or around the portal seals is collected by a set of french drains whose discharge rate is largely independent of the mine pool elevation. This seepage was enhanced after a "breakthrough" that occurred during a peiiod of unusually high pool levels. The mine pool recharge rate during winter is about 2.5 times greater than that of any other season; recharge rates during spring, summer, and fall are approximately equal. Mine pool and discharge water quality information, along with bromide tracer tests, suggest that the original main entries discharge piimaiily to the french drains, while the borehole carries the discharge from an unmonitored set of entiies northwest of the mains. The water quality of the east french drain discharge may have been improved substantially after seepage through the alkaline materials used to constmct the pmtal seals.
Abstract. A 3.2-hectare (8 acre) parcel of a reclaimed surface mine in Upshur County, West Virginia has been monitored to evaluate the effect of grout injection on the spoil groundwater hydrologic characteristics and geochemistry.In February and early March, 1990, the site was injected with a pozzolan grout in an attempt to ameliorate acid mine drainage production by encapsulating targeted zones of acid-producing spoil. The spoil aquifer was monitored for water-quality changes and tested to determine the effect of the grouting on the groundwater flow regime, water table and other aquifer properties.The grouting project has the potential to reduce porosity, eliminate large void space, or close connection between voids and consequently to reroute groundwater flow paths and produce changes in the water table configuration. Monitoring was initiated 14 months prior to grouting and continues to the present. Aquifer tests were performed 3 months before and 4 months after grouting to ascertain changes in hydraulic properties caused by the grouting efforts. Slug tests and constantdischarge aquifer (pumping) tests were performed to determine transmissivity, hydraulic conductivity, and other hydrologic parameters of the spoil directly adjacent to and between monitoring wells. The slug tests indicate that characteristics of the spoil aquifer directly adjacent to the monitoring wells were unaffected by the grout injection. The pumping tests indicate that hydraulic conductivity and transmissivity of the spoil between some wells were generally unaffected.
A h5tract, Surface coal mines often face operational or environmental problems when located in close proximity to flooded, abandoned underground mines. A basic understanding of the groundwater flow systems within abandoned mine pools may help surface mine operators assess the probable hydrologic consequences of their operations or evaluate in-situ water quality improvement techniques. Substantially different mine pool flow systems were found at two acid-producing, abandoned underground mines in western Pennsylvania. Mine maps, surface observations, discharge rates, precipitation records, water levels in monitoring wells, and water quality analyses were used to characterize the systems. At one site, the mine pool piezometric surface was horizontal, and most of the mine pool flow occurred through open entries at the base of the system. Water quality analyses and tracer tests indicated that flow was probably no.t uniform through all mine entries, and that flow through monitored entries was relatively slow. At the second site, water levels in monitoring wells showed a distinct water table gradient. This indicated the presence of diffuse flow through caved entries. However, the water flowing from the monitored section of the mine pool may have represented only a small portion of the total flow at the two monitored discharge points. A tracer test revealed a strong hydrologic connection between the tracer injection well and one downgradient well, but the tracer was not detected at the main discharge 6 months after injection. A more detailed assessment of the mine pool hydrology at the second site was not made because of the suspected large size of the pool and the effect of multiple discharges on pool behavior.
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