2008-03-31_PERMIT FILE - C1980007A (34)

Home Browse Search

TVest Elk Mine Three of the six groundwater monitoring wells completed in the Upper Coal Member of the Mesaverde Formation are currently monitored. These wells include SOM-2-1-1, SOM-16-H, and. SOM C-76, which are all completed in the F Seam. SOM-23-H-2 was completed in the E Seam and removed from the monitoring program in June 1998. MCC reinitiated monitoring of well SOM-23-H-2 in 2005. • Table 5 Summary of Pumping Test Data well Date of Test Geologic Unit Tested Hole Type Pumping Rate Yield Estimated Transmissivi SOM C76 10/18/75 F Seam Cased 3 pm 0.012 m/ft. 16.68 pd/ft. SOM C76A 10/29/75 F Seam & Barren Member Cased 3 gpm 0.012 gpm/ft. --- SOM 22-H-2 09/25/74 Barren Member Cased 0.75 m 0.003 m/ft. 2.46 d/ft. SOM 22-H-3 05/19/75 F Seam Cased 1 Q pm --- --- SOM 64 07/30174 Barren Member Open 0.75 m 0.005 m/ft. --- SOM 55 06/11/74 Barren Member Open 0.75 m 0.005 m/ft. --- SOM C35 --- F Seam Cased --- D Hole -- SOM 23-H1 10/08/74 B Seam Cased 1 m --- --- SG-1 11/11/76 Sylvester Gulch Alluvium Cased 1 gpm --- 121 gpd/ft. R-1 11/01/75 Rollins Sandstone Open 3 pm --- -- R-1 05/26/76 Lower Coal Member" Cased 120 m 3.3 m/ft. 1723 d/ft. AL-1 05/27176 North Fork Alluvium Cased 17.4 pm -- 498 pd/ft. SOM 23-H2 10/09/74 E Seam Cased 0.6 m --- - Notes: (1) Same hole as C76 only open to Barren Member and F Seam 2 Suspected connection with North Fork Alluvium In addition to these wells, two additional groundwater monitoring wells were completed in the Upper Coal Member in 1996. These wells include 96-27-1, completed in the E Seam, and 96-2-2, completed in the sandstone above the E Seam. Unfortunately, the well casing for 96- 27-1 collapsed between September 2001 and April 2002 (likely as a result of B Seam mining beneath it) and is no longer functional. Pumping tests have been conducted on four wells completed in the F Seam coal within the Upper Coal Member of the Mesaverde Formation. Pumping-test analysis from well SOM-C-76 indicates a pumping rate of approximately 3 gpm could be sustained. The result of this analysis indicates that the permeability of the formation is approximately 200 feet per year (2 x 10-4 cm/sec). This information is contained in Table 6. Factors responsible for the water level changes are unknown at this time (Mayo and Associates, 1999). The only slug test that has been completed on the E-Seam has been in well 03-11-1E. A rising head permeability test was completed in this well in 2003 and the calculated hydraulic conductivity was 5x10-' crn/sec (0.14 ft/day). Based on observations during drilling and development of well SOM-3E, the estimated hydraulic conductivity of the E-Seam is about 1x10 6 cm/sec (2.3x10 3 ft/day). During development activities the flow from SOM-3E was less than 0.5 gallons per minute (gpm) (HydroGeo, 2003). A review of the hydrograph for well SOM-23-1-1-2 indicates that, from the time of construction in 1974 through to the present, observed water levels have consistently been at the bottom of this particular well. According to information obtained at the tune the well was constructed, the well was producing approximately 0.6 gpm. Water level 2.04-67 Revised June 2005 PR10, March 2006; Rev. April 2006 PRIO, Sep. 2007PR12