2012-07-16_HYDROLOGY - M1977036 - Laserfiche WebLink

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Ms. Kristina Wynne Greeley 35th Ave /Iverson Combined SWSP July 16, 2012 Iverson Pit Page 3 The depletions that result from the mining operation at the Iverson Pit are evaporation from exposed surface area, and water lost in mined product. Any water lost with dust control activities were accounted for under the 35th Ave Pit with the exception of any water diverted from dewatering activities and used for dust control. Those losses were included as part of the dewatering analysis. There are no areas of pre -81 ground water exposure at the Iverson Pit. Gross evaporation at Iverson Pit is estimated to be 43.8 inches, or 3.65 feet per NOAA Technical Report NWS 33 with an effective precipitation amount of 14.35 inches, or 1.2 feet per year based upon Greeley UNC, CO (ID #3553) NOAA weather station for the timer period of 1967 -2010. The total annual net evaporation is then 2.42 feet per year. For the SWSP request period, the total net evaporation projected to occur from Iverson pit is 1.43 acre -feet. This loss is based on a settling pond of 0.07 acres and dewatering trenches measuring 0.38 acres from June through December 2012 and then measuring 0.57 acres from January through May 2013. The applicant projects mining 99,195 tons of washed aggregate and 389,275 tons of crushed (not washed) aggregate during the SWSP request period. The washed material is assessed a 4% water loss by weight and the not washed material is assessed a 2% water loss by weight for a total water loss of 8.64 acre -feet during the SWSP request period. No additional losses for dust control or the concrete batch plant are projected aside from those already included with the 35th Ave Pit. In all, Iverson Pit is expected to have a water loss of 10.07 acre -feet over the SWSP request period. The Iverson Pit depletions must be lagged back to the Cache La Poudre River as depletions from the site do not occur instantaneously. A stream depletion model using the Glover method was used to calculate the lagged depletions to the Cache La Poudre River. The following parameters were used in the model: transmissivity (T) = 120,000 gallons per day per foot, specific yield (SY) = 0.2, the distance from the Cache La Poudre River to the edge of the alluvium = 2,497 feet, and the distance from the centroid of the pit to the Cache La Poudre River = 333 feet. The total lagged mining depletions during the SWSP period is 9.58 acre -feet. See Table 1 for the monthly breakdown of depletions at Iverson Pit. Replacements The source of replacement water will primarily be from a 125 acre -feet lease of fully consumable effluent water from the City of Greeley ( "Greeley "). Lafarge traded its 550 Boyd and Freeman Ditch shares for 125 acre -feet of augmentation water from Greeley. MMM acquired this lease from Lafarge as part of their acquisition of the Greeley 35th Ave Pit. The lease allows MMM to use this water to cover depletions at 35th Ave Pit and surrounding land. Thus they will be using this lease to cover depletions at Iverson Pit. Fully consumable replacement water is to be provided by Greeley and it will be returned to the river at one of the following locations: a) Greeley Water Pollution Control Facility Outfall (WDID 0302312) located on the Cache La Poudre River; b) JBS Swift Industrial WWTP Outfall (WDID 0102342) on Lone Tree Creek; c) confluence of the 35th Avenue Drainage Ditch and Cache La Poudre River or any augmentation station /release structure(s) to be constructed in the vicinity of such confluence and associated with Greeley's operation of reservoirs knows as Flatiron Reservoir Nos. 1 -5 (a.k.a. Poudre Ponds /Greeley West Pit/Greely 25th Ave Pit); d) an augmentation station /release structure located under the Boyd and Freeman Ditch and approved by the water commissioner and division engineer for such purpose; e) release structures from Greeley Canal No. 3 as described in Greeley's decree in case no.