2009-04-13_REVISION - M2008012 (17)

Home Browse Search

Appendix E. Groundwater Monitoring Aquifers in the Paradox Basin typically behave as unconfined where the formations outcrop at the surface which is the case in the project area. Recharge is typically from precipitation through surface outcrops along the edge of valleys and infiltration along river channels (Topper et al., 2003). Typically, groundwater flows from the outcrop toward the direction of major streams (Robson and Banta, 1995). Bedrock of the Morrison formation underlies the project area. The Salt Wash member of the Morrison is the target zone for mining exploration at the Last Chance site. The Salt Wash member consists primarily of interbedded sandstones, siltstones, and mudstones. In the Paradox Basin, these sandstones can serve as aquifers separated by the siltstone and mudstone beds. However, Salt Wash sandstones at the project site are relatively dry probably because they are located on the relatively small Davis Mesa where recharge would be minimal. Since the Salt Wash outcrops along the edges of the mesa, any groundwater would not be easily contained for long within these sandstones. In fact, no groundwater has been encountered in existing shafts at the Last Chance Mine. The Salt Wash member is underlain by the Summerville formation which consists of relatively impermeable shale that is several hundred feet thick. Thus, the Summerville acts as an aquitard inhibiting downward percolation of most groundwater from the Salt Wash sandstones to aquifers which are several hundred feet below. Nuvemco contracted the drilling of two groundwater monitoring wells on Monogram Mesa to investigate potential groundwater under their claims that might be impacted by drilling and/or mining operations in the area. Locations and design were chosen with the assistance and agreement of Mr. David Bird, DRMS Hydrologist. Wells were drilled by Little Maverick Drilling Company and constructed by Nuvemco under the direction of professional geologist E. Thomas Cavanaugh (CPG 10493). The monitoring holes drilled on October 1, 2008 are located in the SE/4 Section 18, T. 46 N., R. 17 W as shown on a portion of the USGS Bull Canyon Quadrangle on the next page. Monogram Monitoring Hole Number 1 (MMW1) was drilled in the NE1/4 SE1/4 under Colorado Division of Water Resources (CDWR) Notice of Intent to Construct Monitoring Hole permit 48088-MH, and MMW2 was located in the NW1/4 SE1/4 pursuant to NOI 48032-MH. Both wells are currently dry and will be monitored at least quarterly for one year. Should DRMS require permanent monitoring wells at these locations, the holes will be converted to Monitoring Wells and requisite forms filed with the CDWR. Note that MMW1 initially had about 20 feet of water in the casing. As water was hand bailed for samples, it did not recharge. All of the water bailed was collected and submitted to Evergreen Analytical, Inc. for analysis in spite of not being able to purge the well. Water quality was poor and shown to exceed drinking water standards in Iron, Manganese, Molybdenum, Uranium, Vanadium, Sulfate, and total dissolved solids (TDS). The preliminary results follow. Surface Water No perennial water resources (including wetlands and riparian zones) exist within the project area. The hydrological regime in the vicinity of the project area is such that surface water flows