The Effect of Grout Injection on Mine Spoil Groundwater Hydrology

Abstract

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.

Application of an Analytical Ground Water Flow Model to a Pseudokarst Setting in a Surface Coal Mine Spoil

“…Simulated heads at base-flow conditions for 1989 were about 12% different tha)l measured values (RMS error 0.82 m); the 1990 simulation was somewhat better, with an average head difference of less than 10% (RMS en-or 0.66 m). This may reflect the previously-stated conclusion of Hawkins, et al (1991) that the slug injection tests yielded somewhat more accurate values of hydraulic conductivity. In both simulations, some of the largest errors occurred in the two wells closest to the outslope (wells 3 and 14) and in well 11, which was close to the point where the spoil intercepted the large fracture.…”

“…Table 1 compares the hydraulic conductivity values obtained from these tests. The differences between the hydraulic conductivity values in table 1 were determined by Hawkins, et al (1991) to be related more closely to the test method and instrumentation used than to the effects of grouting, with the 1990 values being somewhat more accurate. However, in order to assess the sensitivity of the model to the results of the field data collection efforts, calibrations were performed for both the 1989 (slug withdrawal) and 1990 (slug injection) periods, using the low-flow heads and discharge values for the two years as calibration goals.…”

Scatterscore: A Reconnaissance Method To Evaluate Changes In Water Quality

“…The deposition of CUB or a CUB grout can also reduce the permeability of mine strata, diverting water away from acid-forming materials. Studies at field sites have indicated limited reduction in the generation of AMD but have not addressed the overall impact on water quality (Ackman et al, 1996;Hawkins et al, 1991;Kim and Ackman, 1994).…”