2010-12-17_REVISION - C1981019 (153)

Home Browse Search

54 Groundwater Aquifer characteristics were measured by WMC on all of the new monitoring wells and piezometers using falling head slug and single well pumping tests. Testing methods for these wells are listed in Table 5.6, and described below. Slug tests were performed on 15 bedrock piezometers (PC prefix) and valley fill monitoring wells by measuring the static water depth, rapidly injecting a known volume of water into the well, and then monitoring water levels as the water - bearing unit equilibrated. Appendix 5.17 provides a detailed description of the single well test protocol employed by WMC. Water level data and the aquifer test analysis graphs are presented in Appendix S.F. Results are summarized in Table 5.6. Single -well pumping tests were conducted in the bedrock monitoring wells (MWC prefix) in conjunction with well development and sampling. The tests were performed by inserting a submersible pump into the well to the top of the screen. Water levels were monitored during the tests using a pressure transducer and data logger. The typical duration of the single -well pumping tests was one to two hours. The WMC protocol for short -term pumping tests is provided in Appendix 5.F. Data were analyzed using a variety of methods, including the Theis confined, Cooper - Bredehoeft- Papadopulos, Bower -Rice, Jacob - Cooper, and Papadopulos- Cooper. Water level data and the aquifer analysis graphs are presented in Appendix 5.F. Results are presented in Table 5.6. To further the understanding of the hydrogeology and groundwater flow regime in the vicinity of the pilot dewatering well, C- 04 -16B was logged using a downhole flow meter. After insertion of the flow meter into the well, a pump was installed to a depth of about 350 ft (i.e., about 70 ft below the water level in the well). The flow meter log was performed on the completed well using a Century Geophysics 9721 probe under static and pumping conditions. The flow meter uses a rubber skirt to isolate flow through a 1 -inch diameter tube equipped with an electromagnetic flow meter. The flow meter test was performed twice. The first test was a trolling log, where the flow meter was pulled from the bottom of the well to the pump at a constant velocity of 15 ft/minute. Based on observed variations in vertical flow as a function of the depth of the trolling flow meter, a second test was performed at 21 discrete depth intervals while pumping the well at a constant rate of 3.5 gpm from the top of the water column. In summary, the data from the pumped flow meter test shows that 1.1 gpm come from below 344 ft and 2.4 gpm coming from above 344 ft. The source of groundwater flow is the Gb, Ga, G7, G8, G9 and Fab coal seams, with the largest increase in flow originating near the Fab seam. Total flow of these units totals approximately 5 gpm. Of this amount, approximately 3.9 gpm is lost into the F sandstone and F coal seams below 344 ft. A more complete description of the test method and results is presented in Appendix 5.G. 2572 -R2 Water Management Consultants