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Holcim South Platte Combined SWSP September 18, 2025 <br /> Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, Ft 6243 Page 19 of <br /> 37 <br /> by Walt Flanagan Ft Company in 1977 and little is known about the use of the shares after <br /> that time. The historical consumptive use analysis utilized a parcel-specific analysis for the <br /> period of 1919 to 1977. A total of 40 shares were used on the Montandon parcel prior to <br /> 1964, with 10 shares being sold off in 1964. The historical consumptive use analysis assumed <br /> that the subject 30 shares irrigated 75% of the Montandon parcel (36.5 acres) prior to 1964 <br /> and 100% of the parcel (48.7 acres) from 1964 to 1977. The crop mix for the Montandon and <br /> Palombo parcels was assumed to reflect the mix of crops for the Fulton Ditch as a whole as <br /> identified in the 1956 CDSS irrigated lands GIS layer, consisting of 44% alfalfa, 26% corn, 15% <br /> dry beans, 13% pasture grass, 1% small grains, and 1% sugar beets. The Applicant previously <br /> utilized an assumed ditch loss of 20% and an irrigation efficiency of 65%. For the purposes of <br /> this SWSP, the Applicant has provided a revised analysis utilizing an assumed irrigation <br /> efficiency of 50%. Based on the above, the historical consumptive use of the 62 Cooley <br /> Gravel shares is estimated as 1.5 acre-feet per share. Return flow obligations were allocated <br /> as 50% surface return flows and 50% subsurface return flows. <br /> Holcim has provided a memorandum dated December 29, 2022 with a historical consumptive <br /> use analysis of the 22 CAMAS shares. The historical consumptive use analysis utilized a <br /> parcel-specific analysis for the period of 1919 to 1971 . The shares were purchased by Adams <br /> Aggregate in 1971 and little is known about the use of the shares after that time. A total of <br /> 45 shares were used on the CAMAS parcel during the study period to irrigate an average of <br /> 81 .9 acres of alfalfa and pasture grass. The parcel contained primarily loam soils and an <br /> average water holding capacity of 1 .5 inches per food was assumed. For the purposes of this <br /> SWSP, the Applicant has assumed an irrigation efficiency of 50%. Based on the above, the <br /> historical consumptive use of the 22 CAMAS shares is estimated as 1.52 acre-feet per share. <br /> Return flows were allocated as 75% surface return flows and 25% subsurface return flows. <br /> The historical return flows from the Cooley Gravel shares and the CAMAS shares were added <br /> together to develop a single set of return flow factors. <br /> The 84 shares to be used for replacement purposes under this SWSP will be delivered <br /> through the augmentation station owned by the South Adams County Water Ft Sanitation <br /> District located just downstream of the ditch headgate. The expected consumptive use <br /> credit for the 84 Fulton Ditch shares for 2024 has been estimated to be 2.40 acre-feet per <br /> share or approximately 202 acre-feet for all 84 shares, which is less than a dry-year farm <br /> headgate delivery of 2.66 acre-feet per share or approximately 224 acre-feet for the 84 <br /> shares. After accounting for return flow obligations, the total consumptive use credit for the <br /> 84 shares is projected to equal 106.06 acre-feet in 2025. In the event the Fulton Ditch goes <br /> into Sections, the Applicant must make up any temporary shortfalls with other sources. <br /> City of Arvada Lease <br /> Holcim has a lease of 66.0 acre-feet of fully consumable surplus return flows from the City <br />