Laserfiche WebLink
Inouye Pit SWSP Page 2 of 7 <br /> March 24, 2022 <br /> evaporation do not occur in the unforeseen event, or events, that would lead to the abandonment of <br /> the Pit. <br /> Depletions <br /> The projected depletions for the period of this SWSP consist of net evaporation from exposed groundwater <br /> surface area, water removed in the mined product, dust suppression, past dewatering and water used for <br /> the slurry wall construction. <br /> Evaporation <br /> The Applicant proposes to replace evaporation from exposed groundwater at the site based upon <br /> evaporation atlases in NOAA Technical Report NWS 33 and the SEO monthly distribution factors for sites <br /> below 6,500 feet. Gross annual evaporation at the gravel pit location is estimated to be 44.00 inches per <br /> year. Net evaporation is defined as gross evaporation less the consumptive use of water by vegetation that <br /> naturally occurred at the site prior to construction of the pit. The historical consumptive use was assumed <br /> to be equal to the effective precipitation (8.4 inches), which was estimated based on the data from the Ft. <br /> Lupton and Brighton NOAA weather stations (period of record 1950-2018). The operation will expose 15.4 <br /> acres of groundwater associated with the silt storage pond in the southwest part of the site and an additional <br /> 0.5 acres exposed from the dewatering trench and large sump area, for a total exposed area of 15.9 acres. <br /> Assuming that there are no evaporative losses in the months of January and December due to ice cover <br /> based on historical temperature data, the net evaporation from the exposed water surface is estimated at <br /> 44.4 acre-feet for this SWSP period, as shown in Table 1 (attached). <br /> However, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the <br /> exposed groundwater surface area that may occur during the assumed ice-covered period (the months of <br /> January and December) for any time that the pit is not completely covered by ice. Computation of the net <br /> evaporation during any time that the pit is not completely covered by ice shall be determined as the pro- <br /> rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer's <br /> General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount <br /> of the effective precipitation for that period. <br /> Dust Suppression <br /> The estimated water used for dust suppression monthly is 0.24 acre-feet and annually is 2.9 acre-feet, as <br /> shown in Table 2. <br /> Water Lost with Mined Product <br /> Though the slurry wall is anticipated to be constructed in 2022, the Applicant conservatively anticipates <br /> that approval of the liner may not be completed during the SWSP period. Therefore assuming the liner <br /> approval does not occur during this SWSP period, it is assumed water is lost with the mined product removed <br /> from the mine site. The Applicant projected that they will produce a total of 750,000 tons of gravel per <br /> year during the SWSP period. Gravel mined will be in a dewatered state and will be washed therefore the <br /> groundwater lost with the mined product during this period is estimated at 4 percent by weight. The water <br /> lost with the mined product is projected to total 22.1 acre-feet for the SWSP period as shown in Table 2 <br /> (attached). <br /> Slurry Wall Construction <br /> The estimated water used for slurry wall construction is 3.50 acre-feet/month during April, May, and June <br /> 2022. The total estimated water usage is 10.5 acre-feet for this SWSP period. Because the Applicant <br />