2024-06-18_HYDROLOGY - M1977436 - Laserfiche WebLink

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Holcim South Platte Combined SWSP June 18, 2024 Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, i± 6243 Page 14 of 26 all 84 shares, which is less than a dry-year farm headgate delivery of 2.66 acre-feet per share or approximately 224 acre-feet for the 84 shares. After accounting for return flow obligations, the total consumptive use credit for the 84 shares is projected to equal 114.20 acre-feet in 2024. In the event the Fulton Ditch goes into Sections, the Applicant must make up any temporary shortfalls with other sources. Brighton Ditch Holcim has previously used 1.038 shares in the Brighton Ditch Company owned by the City of Westminster for augmentation purposes. The lease with the City of Westminster was not extended for this SWSP approval period; however, Holcim must continue to replace return flow obligations from the past use of the shares. The historical return flows will be replaced in accordance with the return flow factors identified in paragraph 35.F of the decree entered in case no. 2016CW3186. The return flow obligations have been replaced under prior SWSPs. City of Arvada Lease Holcim has a lease of 65.0 acre-feet of fully consumable surplus return flows from the City of Arvada, which will be released from the outfall of the Robert W. Hite Treatment Plant to the South Platte River at a rate not to exceed 2 acre-feet per day from July 1" through October 315t Patterson Ditch Holcim has provided replacement water for the DPG Pit using the consumptive use associated with 8 out of 15 shares of the Delta Irrigation Company, the owner and operator of the Patterson Ditch, which were previously used for irrigation within the mining permit boundary. The fully consumable portion of the water associated with the shares will be delivered directly to the river for immediate credit, or delivered to a recharge pond for lagged recharge accretion credits, resulting from the delivery of water to the onsite recharge ponds under free river conditions with the knowledge and approval of the water commissioner. The Applicant submitted a historical consumptive use ("HCU") analysis with the 2021-2022 DPG Gravel Pit SWSP request, which was revised and updated in the 2022-2023 DPG Gravel Pit SWSP request. The analysis was performed for all 15 of the DPG Farms shares in the Patterson Ditch. The period of analysis selected was from 1990 through 2016. The DPG Farm is the last farm on the Patterson Ditch and all water returned to the ditch will flow back to the South Platte River via the Patterson Ditch wasteway located approximately 500 feet down-ditch. The HCU analysis performed for the use of the 15 shares on the DPG Farm indicated that the Patterson Ditch system was generally water-long. The 15 shares owned by DPG Farms yielded in excess of 6.5 acre-feet of water per irrigated acre. This "extra" water would have been available for other shareholders to divert, or would have been left in the ditch and turned back to the South Platte River at the end of the ditch wasteway. Due to this historical practice, a demand-based analysis was used to quantify historical consumptive use and historical return flow patterns for the shares. The modeled farm headgate delivery was determined as the lesser of the Patterson Ditch pro-rata farm headgate delivery and the calculated farm headgate delivery (calculated as the crop irrigation requirement divided by a 45 percent irrigation efficiency) for each month in the study period.