2016-06-15_INSPECTION - M1977141 (2)

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Ms. Tracy Kosloff" Re:1.),ons Quarq S11;SP Renewal Request May 25, 2016 Page 2 of 4 Replacement sources for this plan will consist of Colorado-Big Thompson water leased from the City of Foil Collins. DEPLETIONS Evaporative loss will occur from the pond water surface. The surface area of the pond is approximately 0.3 acres. The NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States (U.S. Department of Commerce) was used to determine gross evaporation. For this location, the annual evaporation is approximately 37.0 inches. Monthly evaporation percentages as suggested by the Office of the State Engineer were used to calculate gross monthly evaporation from the pond. Average monthly precipitation data was obtained from the Norther Colorado Water Conservancy District (NCWCD) Longmont West station.' The average monthly precipitation was adjusted to total 17" per year to reflect average annual precipitation at the Lyons Quarry location per the average precipitation isoline layer on the Colorado Decision Support System (CDSS).2 Effective precipitation was calculated as 70%of average precipitation. Average monthly air temperature data was also obtained from the NCWCD Longmont West station, located at an elevation of 5,062 feet. The average monthly air temperature was adjusted to the 5,590 foot elevation of the Lyons Quarry by applying a 3.6°F reduction for every 1,000 foot gain in elevation. During months when the adjusted average monthly air temperature was less than 32'F, it was assumed that the pond is frozen over and evaporation does not occur. The net evaporation rate was calculated as gross evaporation minus effective precipitation, and is estimated to total 22.38" per year. As shown in Table 1, for the 0.3 acres of pond surface area, total depletions are estimated to equal 0.52 acre-feet during the requested plan period. Given the close proximity of the pond to South St. Vrain Creek, the narrow nature of the alluvial aquifer in this area, and the likely coarse-grained nature of the aquifer material itself, it was assumed that evaporative loss would impact the stream system more or less instantaneously. REPLACEMENT SOURCES Aggregate has secured a lease of 2.0 acre-feet of Colorado-Big Thompson (C-BT) water from the City of Fort Collins, and has received approval from the Northern Colorado Water Conservation District (NCWCD) to use this C-BT water for replacement purposes in this SWSP. A copy of the lease and NCWCD's approval are attached. The C-BT water will be delivered to St. Vrain Creek via the St. Vrain Supply Canal. Because the C-BT water is being leased from the City of Fort Collins, replacement credit will be determined as 50% of the net delivery. The replacements will enter the stream downstream of 'httR:1/►vww.northernwater.org/WaterConservation/WeatherandFTinCo.aV.- accessed May 4,2016. 2 http://cdss.state.co.us,accessed May 4,2016.