2019-12-03_HYDROLOGY - M1983090 - Laserfiche WebLink

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Poudre Pits SWSP December 3, 2019 Plan IDs 3218 Et 4585 Page 2 of 9 trenching, which is included in the La Poudre site depletions for the West Site. Dewatering water will be delivered to recharge in the West Lake/Wildlife Lake located in the western portion of the La Poudre site. It is assumed that 33% of the water pumped into the lake will recharge into the West Lake and 67% will be discharged from the lake directly to the river. No mining is proposed to occur at the North La Poudre site during this plan period. Depletions Evaporation and Operational Losses During this SWSP period, depletions at the La Poudre and North La Poudre Pits will consist of evaporation losses and production depletions. The depletions for each site are shown in the following table: Table B - 2020 Site Depletions (acre-feet)' Water Water Total Site Name Evaporation Lost in Consumed Dust Total Lagged Losses Mined in Concrete Control Depletions Depletions Product Batchin West 14.36 2.94 0 2.20 19.5 20.3 La Poudre Middle 3.66 0 0 0 3.66 3.66 East 34.29 0 0 0 34.29 34.29 North La Poudre 20.47 0 0 0 20.47 21.14 Total 72.78 2.94 Ob 2.20 77.92 79.35 a Depletions shown do not include those from past or projected dewatering operations at the sites. 'Water for concrete batching is supplied from municipal taps. For the purposes of this SWSP, depletions are assumed to impact the Cache la Poudre River perpendicular to the point of depletions, which is considered to be the centroid of the exposed surface area at each site. Evaporative depletions for each site were calculated using a gross annual evaporation of 38.5 inches, with a credit of 9.78 inches for effective precipitation (based on an average annual precipitation of 13.97 inches for the Windsor weather station). The West Site includes a 4-acre Wildlife Pond and 2 acres of dewatering trenches associated with the West Lake/Wildlife Pond and the Lee Parcel; the Middle Lake contains a 1.53-acre pond; and the East Lake contains a 14.33-acre pond. The La Poudre North site contains a 2.35-acre pond and a 6.2-acre pond. The attached Figure 1 shows the location of each of these exposed groundwater features. Operational losses at the La Poudre and North La Poudre sites will consist of 2.20 acre-feet of water for dust control and 2.94 acre-feet of water lost with 100,000 tons of mined aggregate. The aggregate is mined below the water table and is washed; therefore the water retained in the mined product is considered to be 4.0% of the mined material by weight. Water for dust control will be pumped from the West Lake within the La Poudre site. Operational activities at the site will include concrete batching, but no groundwater is anticipated to be used for this purposes as two domestic water taps are currently enough to supply the estimated water requirements for the projected 105,000 cubic yards of concrete. Depletions from the La Poudre and North La Poudre Pits will impact the Cache la Poudre River upstream of the Whitney Irrigation Ditch (WDID 0300930).