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

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test analysed by the McWhorter method on the overburden and coal zone. The results of this test indicated a hydraulic conductivity of 2.1 ft /day for the two zones combined, (see Table 7 -5, pg 7- 22 of the New Horizon 1 Mine Permit a copy of which is contained in the Appendix 2.04.7 -1 to this Section). Estimating discharge from the overburden, coal, and underburden zones into the NHN pit can be based on the average overburden zone aquifer characteristics. For the overburden, the average hydraulic conductivity (or K) is 0.72ft /day. The pit length will be about 2,197 feet long. The average saturated thickness of the overburden zone just north of the highwall is about 16 feet. The average gradient in the overburden just north of the highwall is about 0.05. Based on the existing overburden characteristics, the annual discharge from the highwall is calculated using Darcy's Law Q = (K)(gradient)(cross sectional area of discharge). Therefore, Q (or discharge) for the overburden zone is equal to 0.72ft /day x 0.05 x (16.0 ft x 2197 ft) or about 911 ft3 per day or 323,515 ft3 per year. The average thickness of the coal zone is about 9.0 feet and the average K value is 0.19 ft /day. The hydraulic gradient averages about 0.051 and the pit length is the same at about 2,197 feet long. Using the same methodology, the discharge from the coal zone is about 192 ft3 per day or about 70,080 ft3 per year. The average hydraulic conductivity for the underburden is 1.61 ft /day and the average hydraulic gradient is 0.056. The thickness of the underburden is about 6.0 feet. Discharge from the underburden into the pit using the same methodology would be about 1188 ft3 per day or about 433,620 ft3 per year. Based on these calculations, the annual discharge into the pit would be about 836,215 ft3 per year or an average of about 11.9 �pm. As noted, this is based on the situation as is but does not account for the rerouting of 2" Park Lateral through the HDPE pipeline and the suspension of irrigation during mining which will reduce discharge into the pit. The data from the slug test at GW -N9 (overburden and coal zone combined as described above) show a higher K value (2.1 ft/day) than the averages for the overburden and coal zones. As expected, calculating discharge rates from this test results in higher discharge rates than those calculated from the zone averages. Using the K value from GW -N9, an average gradient of 0.05, a saturated thickness of 25.0 feet and a pit length of 2,197 feet the estimated discharge would be equal to (2.1 ft/day) x (0.05) x (25.Oft x 2197ft) = 5767 ft3 per day or 2.105 x 106 ft3 per year or about 29.9cgpm or a factor of 5 higher than that calculated from the averages of the overburden and coal zones of about 5.7 gpm. However, the GW -N 9 location is only 775 feet directly down gradient (see Map 2.04.7 -3) from the 2"d Park Lateral and the test was done on 7/17/86 during the height of the irrigation season and the recharge of the overburden. This suggests that discharge from the highwall after the 2 °d Park Lateral has been diverted through the HDPE pipeline will be closer to the lower discharge rate than to the higher rate indicated from the GW- N9 test data (see Table 7 -5 a copy of which is contained in Appendix 2.04.7 -2). Evapotranspiration Evapotranspiration (ET) is a component of discharge in the NHN area. Studies at the New Horizon Mine with similar vegetation types and uses to the NHN area (see New Horizon 2 permit) indicate that the annual ET rate is on the order of 2.1 acre- ft/acre. Based on the surface area of NHN (321 acres) the annual ET is about 674 acre —ft per year. Irrigation run off water contributes to the stream flow of Tuttle Draw and Coal Canyon. The stream flows of Tuttle Draw and Coal Canyon in turn contributes to the flow of the San Miguel River, at the least, two and one half miles downstream of mining and the proposed mining disturbance. The Section 2.04.7 Page 6 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- 05.docx