2012-06-20_PERMIT FILE - C2010089A (10)

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unweathered overburden at hole GW -N55, GW -N53 shows very little if any response to surface irrigation. This hole produced negligible water during drilling and the recovery from the first water level measurement to the second measurement attests to the low rate of water level recovery at this location. As with the overburden monitor hole at this site the GW -N53 monitoring hole shows that the rates of vertical and lateral recharge of the under burden is low. Map 2.04.7 -6 and Map 2.04.7 -7, respectively, shows the potentiometric surfaces and the direction of flow of the under burden zone at both the lowest level (winter conditions, no irrigation flow) and highest level (summer conditions with full irrigation). The amplitude of the seasonal fluctuation due to irrigation is about 7ft. and 23 ft. for holes GW -N47, and GW -N50, respectively. The gradient of the potentiometric surface varies from about 0.029 ft/ft to about 0.046 ft/ft during the seasonal low levels and 0.0396 ft/ft and 0.055 ft/ft during seasonal high levels. The area directly north of the old Peabody highwall has a low seasonal gradient of 0.024 ft/ft and a gradient during the irrigation season of 0.08. The under burden zone at GW -N47 has an artesian head varying from 34 to 40 ft above the zone from winter to summer The under burden zone artesian head at GW -N50 varies from about 15 ft. to about 39 ft. above the zone from winter to summer Backfill Water Levels. The NHN permit area encompasses part of the area of the old Peabody Nucla Mine, which ceased production in 1983. Over burden backfill material exists south of the old Peabody high -wall. Four holes (GW -N10, GW -N26, GW -N27 and GW -N28). monitored water levels in this backfill material through the end of 1987. All four of these holes were abandoned and reclaimed in November of 2001. Map 2.04.7 -1 shows the backfill monitor hole locations. The backfill is essentially dry with the exception of the area in the vicinity of GW- N27 and GW -N10. At GW -N27 the back fill has approximately 6.4 feet of maximum saturation. At GW -N10 the backfill is dry from time to time with maximum saturation of only slightly more than 1 foot. GW -N27 was installed in August of 1987 and shows seasonal fluctuation of a little over 3.0 ft corresponding with run off from the irrigation flow,( hydrographs for monitor holes GW -10 and GW -27 are contained in the Appendix 2.04.7 -1 of this section). Recharge and Hydrologic Boundaries. The predominate source of recharge to the shallow bedrock zones at the NHN permit area is direct leakage from the 2' Park Lateral irrigation ditch where it crosses the outcrop of each of the respective zones (over - burden, coal, and under - burden), and infiltration of excess flood irrigation waters into the weathered overburden. Minor recharge also results from infiltration of precipitation. Discharge is down dip to the outcrops and old Peabody high -wall. (see Map 2.04.5 -1 of this application).. Although exploration drilling has indicated the presence of faults (see Map 2.04.6 -2), there is no evidence that the faulting is affecting ground water flow. Infiltration and Permeability of the Unsaturated Zone Using the soil hydrologic properties defined by the Soil Conservation Service of the U.S. Department of Agriculture, it is possible to estimate the infiltration rates of soils occurring within the vicinity of the New Horizon 1 & 2 mining areas. The New Horizon 1 & 2 soils have been mapped at a scale of 1 inch equals 400 feet. The soils maps are included in Section 2.04.9 of this permit application. At the adjacent New Horizon 2 Mine, the majority of the soils have a moderate (0.6 - 2.0 in/hr) permeability and infiltration rate. A minor amount of the soils have a moderately rapid (2.0 - 6.0 in/hr) permeability and infiltration rate. The subsurface strata in these areas consist predominately of Section 2.04.7 Page 4 November 2011