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Joanna Williams March 12, 2018 Page 3 4 is currently being stripped and mined. It exposes approximately 1.0 acre of ground water. Mining of the Morton - Holton Lakes Mine is presently expected to last up to fifteen years. DEPLETIONS The projected depletions in Stages 1, 2, 6A, 613, 3 and 4 for the period of this SWSP request are summarized below and consist of net evaporation from the exposed ground water surface area, water used to wash the mined product,and dust suppression. Net Evaporation The net evaporation rate at the Morton-Holton Lakes Mine was determined to be 2.92 ac-ft per year and is equal to the average annual gross evaporation rate minus the average annual effective precipitation rate, as summarized in Table 1. The average annual gross evaporation rate was determined to be 44.27 inches per year based upon NOAA NWS 33 Evaporation Atlas mapping of 1956-1970 average annual free water surface evaporation. The monthly gross evaporation rates shown in Table 1, column 2 were determined based upon the SB 89-120 guidelines gross evaporation distribution for elevations below 6,500 feet (given in column 1). The effective precipitation rate was determined to be 9.25 inches per year based upon 70% of the 1950 to 2014 average precipitation rate of 13.22 inches per year at the Fort Lupton 2 SE (ID: 3027, record: 1950-1976) and Brighton 1 NE (ID: 950, record: 1976-2014) NOAA weather stations. The monthly precipitation and effective precipitation patterns are shown in Table 1, columns 3 and 4, respectively. The monthly net evaporation rates shown in Table 1, columns 5 and 6 are equal to the monthly gross evaporation rates minus the monthly effective precipitation rates. • The northern portion of Stage 1 was allowed to fill in June 2017, and the surface area is now a total of 13 acres, which it will remain at throughout the remainder of the mining plan. • Stage 2 was partially filled in October 2017 and then filled additionally in December 2017 under free river conditions to a total depth of 18 feet and a surface area of 7 acres. If additional free river conditions allow, or other fully consumable replacement supplies are obtained,the surface area of Stage 2 could increase to as much as 14 acres. • Production is currently coming primarily from Stage 4. It is slurry lined and exposes approximately one acre of surface area. • Mining at Stage 6B has been completed. It currently exposes 1.0 acre of surface area. As discussed above, RMCC proposes to partially fill Stage 613 with direct diversions from the South Platte River during free river conditions. The target depth of water in the pond will be a minimum of 12 feet above the bottom of the mine excavation and the surface area will not exceed approximately 5 acres.