2014-05-12_PERMIT FILE - C2010089 (3)

Home Browse Search

total volume of water that could be evapotranspired from the New Horizon Mine vegetation study is estimated under ideal conditions. In reality the evapotranspiration rates are less. In many areas shallow soils and rock ledges restrict rooting depths and inhibit maximum plant growth, thereby reducing ET rates. Aquifer Characteristics of the New Horizon North Mining Area Previous aquifer testing of the Dakota Formation coal strata in the NHN area indicates that the overburden, coal and underburden zone transmissivity and hydraulic conductivity values in the NHN area are low to very low (see Tables 7 -5 and 7 -6 in Appendix 2.04.7 -2 of this application). The overburden and underburden aquifers have the higher values and the coal aquifer has the lowest transmissive properties. There is approximately one order of magnitude range in the transmissivity and hydraulic conductivity values for the overburden, coal and underburden aquifers. This suggests that there is a high degree of spatial variability within the aquifers. Storage coefficients for the various stratigraphic zones vary from about 10-4 to 10 -5 for the overburden and the coal /underburden zones, respectively. Transmissivities (T) for overburden vary from a low of about 13 ft2 /day to a high of about 58 ft2 /day at GW -N9 (located within the NHN permit area). T values for the coal zone vary from 2.4 to 6.0 ft2 /day and the T values for underburden vary from about 3 to 88 ft2 /day. The backfill monitoring well (GW -N27) was completed in the fall of 1987. A short term specific capacity and transmissivity test was conducted at the time of water quality sampling at Well GW -N27. A K -value (hydraulic conductivity) of 40 ft /day and a transmissivity value of 261 ft2 /day was determined (see Table 7 -5 in Appendix 2.04.7 of this application) indicating that the transmissivity in the back fill at this location is 4 to 5 times higher than that of the overburden. The saturated thickness of backfill at this location is about 6.5 feet (see hydrograph for well GW -N27 in Appendix 2.04.7 -1 of this application). The aquifer characteristics (production potential) of the three stratigraphic zones indicate that they are marginal at best for domestic use and totally inadequate as a source for irrigation water. Baseline Ground Water Ouality Prior to drilling the nine ground water monitoring wells (see Map 2.04.7 -1 for locations of monitoring wells GW -N47 through GW -N55) the planned well locations, completion techniques, water quality sampling schedules and the water quality sample parameters were discussed with CDRMS for their input and guidance. Samples for groundwater quality analysis were collected on a quarterly basis from eight of the nine wells; however, monitoring well GW -N55 has been nearly dry to the point that collecting samples from that well is not possible. Water quality sample collections began on October 10, 2008 and will continue for the foreseeable future. The results of the groundwater quality data are reported in Appendix 2.04.7 -1 of this application along with the hydrographs from the nine monitoring wells. The water quality data from the 9 new monitoring wells supplements the water quality data reported in the New Horizon 1 permit documents. Ground water monitoring wells GW -N8 and GW -N9, installed by Peabody for the old Nucla Mine, are within the NHN permit area. Several other monitoring wells, GW -N3, GW- N4 and GW -N4R are in close proximity to the NHN permit area and provide additional water quality information. NHN permit area is isolated from any potential impacts from the adjacent New Horizon Mine as a result of stream incision of the three stratigraphic zones (OB, Coal and UB) by Tuttle Draw. Additionally, the old Peabody Nucla Mine is down dip and down drainage from NHN which essentially eliminates impacts to the NHN permit area from the old mine. From the work that has been done, it appears that another nest of 3 monitoring wells is warranted. The monitoring site would be located in the southwestern portion of the permit area Section 2.04.7 Page 7 October 2013 (TR -05) E: \New Horizon \DRMS \NHN Permit \04 Technical Revisions TR \TR -05 \Documents from Jason \2.04.7 Hydrology Description_TR- OS.docx