2022-03-25_HYDROLOGY - M2017036 - Laserfiche WebLink

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Knox Pit SWSP January 19, 2022 Plan ID 5958 Page 3 of 8 evaporation from exposed groundwater surfaces at the site is projected to total 30.17 acre-feet for this plan period. The applicant may take a credit for the amount of groundwater and precipitation historically consumed by native vegetation on the areas under the free water surface, estimated as 70 percent of the total precipitation measured at the site for each month. This calculated amount would be subtracted from the monthly gross evaporation rate to obtain the monthly net evaporation rate. Water used for truck washing will be pumped from the Water Management Pond. Truck washing will occur on a concrete pad. The water used for this purpose will be recycled, with any runoff being routed to a storm water pond and discharged in accordance with the stormwater pollution prevention permit/plan for the site. Therefore, the only depletion associated with truck washing will be due to evaporation from the concrete pad. The area of the concrete pad has been included in the calculations for evaporation at the site. Water for dust control purposes will also be pumped from the Water Management Pond. You have estimated that beginning in June 2022, a monthly amount of 0.17 acre-feet (55,400 gallons) of water will be required for dust control purposes, based on operations at LRM's Johnstown site. All water used for dust control purposes is assumed to be 100% consumed. The estimated monthly consumptive use due to evaporation from the Water Management Pond, and the combined consumptive use due to evaporation from the Reclaim Pond, dewatering trenches, truck wash pad, and from water used for dust control purposes during this plan period are shown under Evaporation on the attached Table 1. The consumptive use of groundwater for these non-production purposes is estimated to total 31.35 acre-feet for this plan period. The Water Management Pond will be completely dewatered to allow for completion of its construction. The volume of water that will refill the Water Management Pond was calculated as the sum of the volume of water contained in the pond prior to dewatering (29.65 acre-feet) and the votume of the "first fill" of the newly excavated portion of the pond (23.72 acre-feet). The "first fill" is the water that fills an unlined pit or pond and occupies the volume previously occupied by the removed sand, gravet, or other solid material. The "first fill" volume is estimated as the volume of the pit less the pore votume and the water retained in the mined product. You have projected 139,625 tons of mined aggregate will be removed from the site during this plan period. The material will be mined below the groundwater table, but in a dewatered state. The material will be washed, therefore the moisture content is considered to be 4% of the mined material by weight, all of which is considered to be a groundwater diversion. This results in a consumptive use of 4.11 acre-feet for the projected 139,625 tons of washed material. The mined aggregate will be used for the production of an estimated 78,084 cubic yards of concrete at the site during this plan period. A volume of 30 gallons of water is required per cubic yard of concrete produced. Water demands for concrete production are therefore estimated to total 7.19 acre-feet for this plan period. Water used for concrete production is considered to be 100% consumed. The estimated monthly consumptive use due to water removed with the mined aggregate and water used for concrete batching are shown under Production on the attached Table 1. The consumptive use of groundwater for these production purposes is estimated to total 11.30 acre-feet