2022-12-19_HYDROLOGY - M2008082 - Laserfiche WebLink

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Morton Lakes Substitute Water Supply Plan Renewal Page 3 of 9 December 16, 2022 demonstrate you can replace long term injurious stream depletions that result from mining related exposure of groundwater. The DRMS letter identified four approaches to satisfy this requirement. In accordance with approach nos. 1 and 3, you have indicated that a bond has been obtained for the new Morton-Holton Lakes site that can cover the cost of lining, to prevent the exposure of groundwater. The current bond amount for the new Morton-Holton Lakes site is $4,150,000.00. Depletions The projected depletions for Stages 1, 2, 5, 6A, 613, 6C, 6D, 6E, and 7A result from evaporation, dewatering, dust control, water used to wash the mined product, water lost in the mined product, storage (re-fill), and slurry wall construction. Evaporation The Applicant proposes to replace evaporation from exposed groundwater at the Morton-Holton site based upon evaporation atlases in NOAA Technical Report NWS 33 and the State Engineer's Office ("SEO") monthly distribution factors for sites below 6,500 feet, as shown in attached Table 1. Gross annual evaporation at these gravel pit locations is estimated to be 44.27 inches per year based on the NOAA NWS 33 Evaporation Atlas mapping (1956-1970). Net evaporation is defined as gross evaporation less the consumptive use of water by vegetation that naturally occurred at the site prior to construction of the pit. The historical consumptive use was assumed to be equal to the effective precipitation of 9.25 inches, which was estimated based on the data from the Fort Lupton 2SE (ID 3027, record 1950-1976) and Brighton 1 NE (ID 950, record 1976-2014) NOAA weather stations. The projected maximum monthly exposed groundwater surface area at each stage is described in Table A below: Table A- Maximum monthly exposed groundwater surface area (acres) Stage 1 Stage 2 Stage 5 Stage 6A Stage 6B Stage 6D Stage 6E Stage 7A Total 11.0 15.0 1.0 0.2 0.2 2.0 0.2 1.0 30.6 The net evaporation rate for the exposed water surface is estimated to be 2.92 acre-feet/acre, as shown on attached Table 1. Total net evaporation for this plan period is 89.31 acre feet, as shown on attached Table 2, Column 2. Mined Product In addition to the evaporation, water is lost with the mined product removed from the mine sites as shown in attached Table 2. Brannan projects that they will mine 1,480,000 tons of gravel during this plan period from Stages 5, 6D, and 7A within the lined pits which will result in a depletion of 2% by weight. The water lost from mined product is projected to total 21.79 acre-feet during 2023 as shown in Table 2, Column 4. Dust Suppression The estimated water used for dust suppression is 26.95 acre-feet during 2023, as shown in Table 2, Column 5. Brannan will pump water from Stage 2 for dust suppression purposes during this plan period.