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. • <br />Larry Oehler - 7 - April 4, 1990 <br />Reclamation Resources should use the maximum precipita ion value to <br />be expected during the growing season at the Alma Plac r in the <br />design of their water management system. The Division recommends a <br />value of 2.13 inches/month (18.00/16.40 X 1.94 = 2.13) <br />7. Ground Water Recharge <br />The Alma Placer occurs within a high mountain watershe It is <br />expected that the gravels to be mined consist of a sha low alluvial <br />-~ aquifer recharged from snow+nelt and frequent summer th nderstorms. <br />Reclamation Resources should provide an estimate of re harge to the <br />unlined pond(s) under conditions of both snowmelt and understorms. <br />The greater recharge rate should be used in the pond d sign. <br />8. Evaporation Loss <br />The applicant has classified the proposed operation as a <br />non-consumptive use, with water consumption based enti ely on <br />evaporative loss. The State Climatologists Office rep its a gross <br />evaporation of 30-35 inches per year near Alma. Recla ation <br />Resources should determine an average evaporation amou t for the <br />months of July and August (this will coincide with the natural <br />precipitation value of 2.13 inches). The Division req ests that a <br />weighted evaporative loss for each month be determined based on <br />available temperature data. <br />Seepage Loss <br />The applicant has proposed the construction of unlined ponds for the <br />water management system. The ponds will be cleaned of sediment <br />periodically. Water will be allowed to percolate thro gh the ground <br />and recharge the surrounding alluvial aquifer. <br />Reclamation Resources should determine an average seep ge loss based <br />on the hydraulic gradient of the surrounding aquifer a d hydraulic <br />conductivity of the material in the pond bottom or the surrounding <br />alluvium, whichever is more limiting. Please indicate the expected <br />rate and corresponding volume of seepage loss and dire tion of ground <br />water flow. <br />Impoundment Design <br />Impoundment design including dimensions and side slopes should <br />be provided for each phase of the mining operati n. The design <br />for each phase should be based on the corresponding water <br />balance. The design should allow fora minimum reeboard of <br />1.0 foot above the expected maximum water surfac elevation. <br />Hydraulic calculations used to derive these desi ns should be <br />included in each appropriate water balance. <br />The Division also requests that the applicant pr vide a <br />statement for each phase of mining that the desi n and <br />construction of the water management sy stem has en inspected <br />