2015-03-04_HYDROLOGY - M1979097 - Laserfiche WebLink

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East Rigden Pit SWSP February 27, 2015 not create a credit to be used elsewhere. Page 2 of 6 Water use at the East Ridgen Pit during this plan period will consist solely of water used for dust control purposes at the site. Although material is being excavated from the Fort Collins Parcel, the material will be used to fill elsewhere in the pit or adjacent to the pit and therefore it was assumed that there would be no water loss associated with removal of the mined material. Water for dust control purposes will be pumped from the neighboring Port of Entry Pit (well permit no. 76138 -F, WDID 0303026), which is also owned by the City. The reservoir construction contractor has estimated approximately 500,000 gallons of water per month will be required for dust control purposes while the project is ongoing (March -April 2015), totaling 3.07 acre -feet during this plan period. Depletions from pumping for dust control purposes were lagged from the Port of Entry Pit to the Cache la Poudre River using the Alluvial Water Accounting System (AWAS) program developed by the Integrated Decision Support (IDS) Group at Colorado State University with the following parameters: • Distance from the gravel pit centroid to the river (X) = 450 feet • Alluvial aquifer width (W) = 930 feet • Specific yield (S) = 0.2 • Transmissivity (T) = 55,000 gallons per day per foot In addition, lagged depletions due to past mining and dewatering operations at the East Rigden Pit will continue to impact the stream during this plan period. Depletions from past operations were lagged from the East Ridgen Pit to the Cache la Poudre River using the AWAS program with the following parameters: • Distance from the gravel pit centroid to the river (X) = 2,100 feet • Alluvial aquifer width (W) = 5,800 feet • Specific yield (S) = 0.2 • Transmissivity (T) = 55,000 gallons per day per foot Over 95% of the lagged depletions due to past mining and dewatering operations will have accrued to the river by the end of February 2016. You have chosen to wrap all remaining lagged depletions into this plan period (March 2015 - February 2016) for replacement. Provided that the compacted clay liner for the site receives approval from the State Engineer's Office, no depletions associated with the East Rigden Pit will remain after the conclusion of this plan period and no subsequent SWSP will be required for this site. Wrapped lagged depletions from past mining operations at the site will total 104.66 acre -feet, and lagged depletion from past dewatering operations will total 74.76 acre -feet. Stream depletions from past and projected use at the East Rigden Pit will total 182.49 acre - feet during this SWSP period. A monthly breakdown of depletions is shown in the attached Table 1. Replacements The City of Fort Collins has committed to replace the depletions described in this SWSP from the City's fully consumable sources, as evidenced in its commitment letter that was provided with the SWSP request. Potential sources of reusable water will include Joe Wright Reservoir (WDID 0303678, located in Section 24, T7N, R76W on Joe Wright Creek) water, Southside Ditches water rights, or supplies stored in Fossil Creek Reservoir (WDID 0303774, located in Section 10, T6N, R68W). The following water rights owned by the City, collectively known as the "Fort Collins Southside Ditches Water Rights ", were changed in case no. 92CW129 for all municipal uses and augmentation, replacement, substitution, and exchange.