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Windsor East Mine, Exhibit G – Water Information September 2022 <br /> Page 7 | 11 <br />vicinity can be observed. As noted in Table 4, the result of dewatering at MW-12, located at a distance of <br />approximately 100 ft from the nearest cell, resulted in drawdown of 4.6 ft. This response occurred over two years, <br />since dewatering was variable depending on mining rates. <br />A simplified model assuming a saturated thickness of 8 feet was developed based on the observed impacts of <br />dewatering at the adjacent Parsons mine. Hydraulic conductivity of 0.05 cm/s (representative of a sandy gravel) <br />and a specific yield of 0.2 was used to simulate the aquifer. A head boundary was fixed at a radial distance of 1 <br />mile. Simulation of dewatering of a 500-foot x 500-foot mine cell was performed to reduce the hydraulic head at <br />the mine cell to a hydraulic head 1.5 feet above the top of bedrock. This simulation resulted in a reduction of <br />head at a point 100 ft away by 4.6 ft after approximately two years, which is the same as was observed at MW-12. <br />The isolated effects of propagation of drawdown for various distances at 1 year and 5 years into dewatering is <br />shown below. After 5 years, a new “steady-state” set of conditions has established, minimizing the further <br />lowering of the water table. Drawdown (ft) <br />Distance 1 year 5 years <br />100 ft 4.4 4.8 <br />200 ft 3.6 4.1 <br />500 ft 2.3 3 <br />600 ft 2 2.7 <br />1000 ft 1.3 2.1 <br />2000 ft 0.5 1.1 <br />2640 ft 0.2 0.8 <br />There are likely mitigating factors to this drawdown spread. Active dewatering may stop and start at a location <br />depending on the mining progress, the proximity of the Cache la Poudre River will provide a constant source of <br />water mitigating drawdown impacts, and the aquifer may prove more or less transmissive depending on the <br />location. With this understanding, the modeled spread of the hydraulic effects of dewatering suggests that the <br />impact of the lowering of the water table during mining is unlikely to substantially affect any nearby water wells. <br />1.7 WATER USE <br />Section 6.4.7 of the Colorado Mined Land Reclamation Board's Construction Material Rules and Regulations: <br />(3) The Operator/Applicant shall provide an estimate of the project water requirements including flow rates and <br />annual volumes for the development, mining and reclamation phases of the project. <br />(4) The Operator/Applicant shall indicate the projected amount from each of the sources of water to supply the <br />project water requirements for the mining operation and reclamation. <br />Water use will be at its highest during the mining phase of the project. Mining at the site will intercept <br />groundwater tributary to the Cache la Poudre River. Consumptive uses of groundwater at the site include <br />evaporation from groundwater exposed to the atmosphere, water retained in material hauled off-site for <br />processing, and water used for dust control. <br />Evaporative losses at the site are attributable to exposed groundwater in the dewatering trenches for each mine <br />cell. Evaporative losses were calculated as the difference between gross evaporation and effective precipitation. <br />The NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States (U.S. Department of <br />Commerce) was used to determine the site’s average annual gross evaporation of 43 inches. Precipitation was <br />obtained from the Western Regional Climate Center for the Fort Collins weather station (053005). The gross <br />annual precipitation for this site was determined to be 15.08 inches. Effective precipitation was calculated as 70