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23. The area being mined at any particular time will be dewatered through a <br />system of dewatering trenches. The water in the dewatering trenches will be collected, <br />pumped from the pit, run through either of two sediment ponds, and then, except for <br />relatively small quantities of water used for dust suppression and possibly for the irrigation <br />of an existing meadow that may be cut off from ditch water, discharged into Tomichi Creek. <br />The water surface area at the two sediment ponds is expected to be 0.36 acres. <br />24. The net lake evaporation rate at the Tomichi Pit is calculated in Table 1 using <br />the procedures set forth in paragraph 11 of the DWR Gravel Pit Guidelines with data from an <br />NOAA Technical Report NWS 33 and temperature and precipitation date published for the <br />Gunnison Weather Station. The ice free period was taken as beginning on March 25 and <br />ending on October 25. As shown in column 8 of Table 1, the net lake evaporation rate was <br />calculated at 2.41 feet annually. During mining, the net lake evaporation of the two sediment <br />ponds should therefore amount to no more than 0.87 acre feet annually. <br />25. The initial mining at the Tomichi Pit will occur in an area 400 to 500 feet from <br />Tomichi Creek so Tomichi Creek will be the primary source of the ground water seepage <br />into the mined area. The ground water seepage will be collected in dewatering trenches, <br />pumped from the pit into either of two sediment ponds, and then, except for relatively small <br />quantities of water used for dust suppression and possibly for irrigation of an existing <br />meadow that may be cut off from ditch water, discharged back into Tomichi Creek. Given <br />(1) the short distance between the mining area and Tomichi Creek, (2) the fact that the <br />dewatering system will be operated continuously, (3) the fact that the only depletions to the <br />water collected in the dewatering system will occur as the result of dust suppression and <br />possible irrigation of an existing meadow, both of which will be covered under existing <br />Biebel Ditch rights or the proposed plan for augmentation, the operation of the dewatering <br />system will not result in unreplaced depletions to Tomichi Creek. The Applicant shall <br />continuously operate the dewatering system and shall prevent water from being stored in the <br />gravel pits to the extent that there are out of priority depletions as a result of water stored in <br />the gravel pits. <br />26. The monthly and annual water depletions that will occur at the Tomichi Pit <br />during the period of mine operation are shown in Table 2. These depletions amount to a total <br />of 21.2 acre feet annually, of which 11.4 acre feet will occur during May through September, <br />and 9.8 acre feet will occur during October through April. Assuming a river call is affecting <br />the water uses at the Tomichi Pit during the entire year, these are the depletions that are <br />proposed to be replaced under the Plan for Augmentation. The maximum rate of water <br />depletions during the mining operations will be 0.039 c.f.s. (17.5 g.p.m.) in June. <br />27. After mining and reclamation have been completed at the Tomichi Pit, the two <br />lakes in the reclaimed area will be filled from groundwater seepage when a river call is not <br />occurring. To the extent that the two lakes are filled while a river call is in effect, depletions <br />Case No. 12CW67, Water Division 4 <br />5 <br />