2025-04-14_HYDROLOGY - M1992069 - 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, &t 6243 Page 16 of 37 Table F- Monthly Surface Water (SW) and Groundwater (GW) Return Flow Factors (%) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec SW 0 0 50.0 22.50 36.15 30.32 30.98 22.50 22.50 22.50 0 0 G W 0.71 0.61 0.56 0.63 2.70 4.73 6.99 5.64 3.19 1.79 1.14 0.87 The monthly groundwater return flow requirements will be determined by multiplying the monthly groundwater return flow factor by the total delivery during the previous 12 months. Monthly results shall be divided by the number of days in that month to determine the daily groundwater return flow obligation. The daily surface water return flow requirement will be determined by multiplying the daily delivery of the 1 .5 Smith 6t Emmons shares by the monthly surface return flow factor. Water associated with the 1.5 Smith 6t Emmons shares and water diverted under free river conditions will be delivered to the Lighthouse Cove Pond (WDID 0603018) for recharge. There is an existing return structure to measure deliveries to the Pond. The water commissioner approved the structure on May 16, 2023. The Applicant may not claim recharge credits for any water delivered to the Lighthouse Cove Pond prior to the date of the water commissioner's approval. The expected volume of water available for diversion into the Lighthouse Cove Pond for the subject 1.5 shares is 187.79 acre-feet per year. This figure represents the pro-rata average headgate diversion less a 10% ditch loss. The pro-rata historical consumptive use credit for the 1 .5 shares is estimated to total 91.65 acre-feet for this plan period and the pro-rata return flow obligation for the 1.5 shares is estimated to be 132.56 acre-feet. The Lighthouse Cove Pond (formerly Groom Addition Pit, DRMS Permit no. M-1983-099) is an existing gravel pit pond that is subject to a written augmentation agreement with the Water Users Association of District No. 6. Pursuant to section 37-90-137(11)(b), C.R.S., and case no. 2009CW49, a gravel pit operator or property owner does need to replace water lost through evaporation in excess of the augmentation amount in the written agreement, provided that the operator continually complied with the provisions of the written agreement. The written agreement, dated May 24, 1983, transferred 0.736 shares of the Smith 6t Emmons Ditch Company to the Water Users Association of District No. 6 for the replacement of evaporation associated with 55 acres of exposed groundwater. The delivery of water to recharge in the pond is not anticipated to increase the surface area of the pond or create additional evaporative depletions beyond those attributable to the groundwater exposed to the atmosphere in connection with the extraction of sand and gravel by open mining, therefore