2018-12-26_REVISION - M2008078 (27)

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Page 2of5 43,560 ft2 per acre). There will be evaporation of water from the exposed surface area of the dewatering trench. For purposes of this plan, we have assumed that the exposed surface area for the dewatering trench is 0.5 acres. The water from the dewatering trench will be collected in a 50-foot by 100-foot discharge settling pond. This settling pond surface area measures 0.11 of an acre (50 ft x 100 ft / 43,560 ft2 per acre). Once the sediment in the water from the dewatering trench has settled in the ponds, the water will be pumped into a lateral next to the settling pond and delivered back to the Arkansas River. The maximum exposed surface area from the dewatering trench and settling pond on the mining site is expected to be 0.61 of an acre (0.5 acre + 0.11 acre) and that is the surface area we have used to calculate evaporative losses for this plan. Table 1 shows the monthly evaporation from the exposed 0.61 of an acre within this plan request. The values for Table 1 were obtained from paragraph A.i of Exhibit R of the Lower Arkansas Water Management Association's (LAWMA) decree in Case No. 02CW181. The total annual evaporation from groundwater exposed from 0.61 of an acre of surface area is estimated to be 2.51 acre-feet (0.61 of an acre x 4.11 feet). This amount is also shown in Table 1 and will be augmented under DRMS-M-2008-78. A well permit (Permit No. 75864-F) has been issued for the uses at the mining site for dewatering and exposed pond surface area in accordance with C.R.S. § 37-90-137(2). Water Losses in the Mined Material As part of the operation of the mining of the gravel pit, water is retained in the mined material that is removed from the gravel pit site. The total projected amount of material to be mined from the gravel pit during the proposed term of this plan is anticipated to be approximately 750,000 tons. That estimate is conservatively high as compared to the 624,223 tons of material mined from January 2017 to December 2017. Material mined from the gravel pit has a 2% moisture content since the gravel pit is lined with no groundwater flowing into the pit. Therefore, the total amount of water that will be consumed in the removal of the aggregate from the mining site under this plan is estimated to be 11.04 acre-feet of water ((750,000 tons x 2,000 pounds per ton x 2% / 62.4 pounds per ft') / 43,560 ft2 per acre). Aggregate Washing and Dust Control Groundwater from well SEO Id No. 6705375 is used to wash the aggregate and for dust control at the West Farm Pit site. Depletions from the pumping of this well, as measured through the "B" meter, are augmented at 100% in LAWMA's augmentation plan. This well was added to LAWMA's augmentation plan in Case No. 12CW37. Please see Exhibit B of Case No. 12CW37. Accordingly, the use of water pumped by the well and used at the West Farm Pit will continue to be augmented under LAWMA's augmentation plan and not under this plan.