2010-04-15_HYDROLOGY - M1979191 - Laserfiche WebLink

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Ms. Sira Sartori April 13, 2010 Middle Poudre Combined Plan - Lafarge West, Inc. Page 2 of 8 Kyger Pit M-99-088 03/17/2009 1.7 acres all post 1981 Port of Entry Pit M-82-182 03/17/2009 26.9 acres all post 1981 Shields Mine M-06-064 03/17/2009 1.0 acres all post 1981 The exposed surface area at all the sites has been updated based on the current conditions for each site. The 31.4 acres previously identified as being exposed at the Three Bells Pit Site have never been fully exposed therefore, according to the information provided, the current exposed surface area at this site is only 11.7 acres. The exposed surface area at the Kyger Pit site is from the dewatering trenches around the pit which total to 1.7 acres based on estimated width of 10 feet. For the Shields Mine Site the surface area exposed after December 31, 1980 increased from 0.7 acres to 1 acre based on the dewatering trench outline provided by Lafarge and assuming the trench is 10 feet wide. Mining at the East Rigden Pit has been completed and construction of a clay reservoir liner is in process on the property. The total exposed surface area at this site is 32.1 acres. According to the information submitted, 25 acres of water surface was exposed within the reclamation permit boundary prior to January 1, 1981. This results in 7.1 acres of exposed surface area requiring replacement of depletions from evaporation. The consumptive use at the East Rigden site also includes dust control and a septic system. A storage water right for the East Rigden Pit is pending in Division 1, Water Court case no. 2001 CW202. The Three Bells Pit will include evaporation, water retained in the product and dust control. Mining was re-started at the Three Bells Pit in February 2006 in an area of approximately 20 acres. This site has been continuously dewatered at a rate of 1,200 gallons per minute. The„only consumptive use at the Kyger Pit, Port of Entry Pit and Weitzel Pit sites is the evaporation of exposed ground water. The Kyger Pit has continuously dewatered directly back to the Cache la Poudre River since 2000. The estimated dewatering rate at the Kyger Pit site is approximately 1,,200 gallonsj per minute. Mining is complete at the Weizel Pit site. The Port of Entry Pit site is currently undergoing reclamation. Lafarge West, Inc. filed for a plan for augmentation for the Port of Entry Pit site in case no.- 2004CW111 and this case is currently pending. Lafarge West, Inc. also filed for a plan for augmentation for the Weitzel Pit site in case no. 2002CW205 and this case is currently pending. Shields Mine will include evaporation, water retained in the product and dust control. This site will also be dewatered at a rate of 1,200 gallons per minute. Based on the information from the DRMS file, the Shield Mine will be dewatered into the Fossil Creek Reservoir Inlet Ditch. This ditch lies directly to the west of the Shields Mine. The discharge into the Fossil Creek Reservoir Inlet Ditch is the proposed mitigation to address any drawdown impacts from mining in close proximity of the ditch. The dewatering water is measured and returned to the river from the Fossil Creek Reservoir outlet. The releases shall be measured in a manner acceptable to the water commissioner and the division engineer. Computation of evaporation under this combined plan from December through February was reduced during the ice covered period. You have assumed the ice covered period to occur during the months of December through February, based on the average temperatures of 29°F for December, 27°F for January and 31 OF for February; taken from the Fort Collins weather stations (053005) for the time period from 1900 through 2005. However, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground water surface area that may occur during the