2025-04-14_HYDROLOGY - M2004044 - Laserfiche WebLink

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Holcim South Platte Combined SWSP April 14, 2025 Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, Ft 6243 Page 20 of 37 SWSP, the Applicant has assumed an irrigation efficiency of 50%. Based on the above, the historical consumptive use of the 22 CAMAS shares is estimated as 1.52 acre-feet per share. Return flows were allocated as 75% surface return flows and 25% subsurface return flows. The historical return flows from the Cooley Gravel shares and the CAMAS shares were added together to develop a single set of return flow factors. The 84 shares to be used for replacement purposes under this SWSP will be delivered through the augmentation station owned by the South Adams County Water Ft Sanitation District located just downstream of the ditch headgate. The expected consumptive use credit for the 84 Fulton Ditch shares for 2024 has been estimated to be 2.40 acre-feet per share or approximately 202 acre-feet for 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 106.06 acre-feet in 2025. In the event the Fulton Ditch goes into Sections, the Applicant must make up any temporary shortfalls with other sources. City of Arvada Lease Holcim has a lease of 66.0 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 1st through September 30st 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