2016-02-17_HYDROLOGY - M1996052 - Laserfiche WebLink

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Mr. Rick Parsons, P.E. February 10, 2016 L.G. Everist Combined SWSP Page 7 of 14 On Farm Depletion 0 0 0 1.4 7.5 14.5 16.8 12.9 6.9 1.5 0 0 61.6 of Surface Water Surface Return 0 0 0 0.2 5.4 9.4 15.3 10.0 3.9 0.9 0 0 45.2 Flows Ground Water 0 0 0 0.1 2.7 4.7 7.5 4.9 1.9 0.5 0 0 22.2 Return Flow Lagged Ground 1.5 1.3 1.1 0.9 1.0 1.5 2.3 3.1 3.1 2.6 2.1 1.7 22.2 Water Return Flows 1.5 1.3 1.1 1.1 6.4 10.9 17.6 13.1 7.0 3.5 2.1 1.7 67.4 Total Return Flows Average Net -1.5 -1.3 -1.1 -0.6 10.2 17.3 24.9 14.8 4.0 -1.2 -2.1 -1.7 61.6 Depletion Return Flow Factor 1.1% 1 1.0% 0.8% 0.4% 61.3% 61.3% 58.6% 1 53% 36.3% 1.0% 1.6% 1 1.3% NA Return flow factors for the months of October through April are the percentage of the prior year's farm headgate delivery; those from May through September are the percentage of the month's farm headgate delivery. Based on the historical study period of 1950 through 1997, Table G above provides a monthly summary of the estimated yield associated with the subject 1.41 Rural Ditch shares. The projected annual farm headgate delivery of the subject 1.41 Rural Ditch shares is estimated to be 129.1 acre- feet. The dry-year HCU analysis for the 1.41 shares was determined to be 76.2 acre-feet for 1977 which is greater than the long-term average. The average over 1954-1957 drought was determined to be 64.9 acre-feet. Therefore the average years were used in the HCU analysis. The historical return flow obligation of the 1.41 Rural Ditch shares will be maintained by the plan. LG Everist operates an augmentation station from the Rural Ditch to the St. Vrain (WDID 0502305). The delivery location is below the Last Chance Ditch headgate and above downstream calling water rights located on the South Platte River. You indicated that dry-mining operations at the Rinn Valley Pit site require dewatering at the mining cells and part of the dewatering water is run through the wash plant to process excavated material. There are times when the dewatering trenches at a portion of the Rinn Valley Pit mining site are dry, thus preventing the operator from running the wash plant. Therefore you requested approval to allow L.G. Event to run its changed Rural Ditch water to the mining site to operate its wash plant. You have also requested approval to allow L.G. Everit to use its changed Rural Ditch water for uses associated with the mining operations at the Carbon Valley Pit and Firestone Pit since the three sites are close to one another on the south side of the Saint Vrain Creek. The shares would be used directly at Carbon Valley Pit or Firestone pit. We have reviewed your request and determined that since the Rural Ditch water dedicated to this SWSP was changed as part of the combined plan to allow for use at the Rinn Valley Pit, L.G. Everist is allowed to run its changed Rural Ditch water through the wash plant to process excavated material and potentially use the water at the Carbon Valley Pit and Firestone Pit for uses associated with the mining operations at these sites, provided return flow obligation for the delivery of the Rural Ditch water are maintained by the combined plan, and the use of the Rural Ditch water for augmentation and direct use in the wash plant and other mining operations uses is properly accounted for. In addition L.G. Everist needs to demonstrate that sufficient replacement water sources are available to replace depletions at the Rinn Valley Pit, Carbon Valley Pit and Firestone Pit sites. The approval to run the Rural Ditch water through wash plant and for other mining operations uses is for the 2016 and 2017 irrigation season. Diversion of the Rural Ditch water through wash plant and for other mining operations uses is limited to the historical average diversions and return flow must be calculated using the return flow factors listed in Table G above.