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stream. The discharge from the mine pits will vary through the mining sequence and will • <br />be partly dependent on the ground water stored in the exposed overburden materials and <br />coal seams. Based on the proposed mining schedule, Peabody estimates that the annual <br />mine pit discharge will range from 0.52 acre-foot in 1990 to 13.50 acre-feet in 2002. <br />Stream Depletion <br />As previously mentioned, the industrial water will be derived from the mine pits <br />and runoff due to snowmelt and precipitation and will be stored in Pond 006. The use of <br />this water probably will result in a reduction of the Dry Creek streamflow. To estimate <br />the inflow to Pond 006, the streomflow recorded for the "Hubberson Gulch near Hayden" <br />gage was proportioned according to relative drainage areas. The drainage area of this <br />gage is 8.08 square miles and the period of record is July 1979 through September 1981. <br />The drainage area above Pond 006 is 1.24 square miles. The estimated inflow to Pond <br />006 is 6b.6 acre-feet per year and the monthly inflows range from 0.22 acre-foot in <br />August to 32.1 acre-feet in April. The streamflow records and estimated Pond 006 <br />inflows are shown in Table 4. <br />The period of record for the Hubberson Gulch gage is insufficient to develop a <br />reasonable level of confidence for the estimated inflow to Pond 006. However, the . <br />analysis shows that inflow may be less than adequate to meet the industrial water <br />demands from July through March. Therefore, water pumped from Well No. I will <br />supplement the surface water supplies for the industrial demands. <br />The top of the Trout Creek Sandstone formation at Well No. I is about 530 feet <br />below land surface. The Trout Creek Sandstone is about 200 feet thick at this location. <br />The formation crops out in the Dry Creek basin at a point on Hubberson Gulch about <br />2.5 miles southeast of the well. The formation also crops out at three points on Sage <br />Creek, one point on Grassy Creek, two points on Fish Creek, four points on Trout Creek, <br />one point on Middle Creek, and two points on the Yampo River. <br />GeoTrans, Inc. (hereinafter "GeoTrans") modeled the effects of pumping water <br />from Well No. I (1989, GeoTrans). GeoTrans assumed that the streams were <br />hydraulically connected to the Trout Creek Sandstone at the outcrop locations. The <br />aquifer was modeled for 15 years at a continuous discharge of 35 gpm (56.5 acre-feet per <br />year) followed by 20 years of recovery. <br />The modeling showed that the Trout Creek Sandstone is not hydraulically connected <br />to Hubberson Gulch and, consequently, the pumpoge from Well No. 1 will not affect . <br />4 <br />