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Steamboat Sand and Gravel Pit SWSP Page 2 of 8 <br />March 11, 2015 <br />of disturbed area as shown on Figure 2 (attached). Groundwater was not previously exposed at <br />this site. Alpine anticipates exposing groundwater in the form of a dewatering trench. <br />In accordance with the letter dated April 30, 2010 (copy attached) from the <br />Colorado Division of Reclamation, Mining, and Safety ( "DRMS "), all sand and gravel <br />mining operators must comply with the requirements of the Colorado Reclamation Act <br />and the Mineral Rules and Regulations for the protection of water resources. The April <br />30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate <br />you can replace long term injurious stream depletions that result from mining related <br />exposure of ground water. <br />In accordance with approach no. 4, you have provided an affidavit dated <br />December 13, 2011 that indicates that 1.38 cfs of the Suttle Ditch and 1.0 cfs of the <br />Weiskopf Ditch water are dedicated for use as sources of replacement water solely for <br />this SWSP for as long as there are depletions at this gravel pit site, or until such time as <br />another replacement source is obtained. A copy of this affidavit is attached to this letter. <br />For the purpose of this SWSP, this affidavit will be accepted for the dedication of the <br />shares; however, if the State Engineer determines that a different affidavit or dedication <br />process is necessary to assure proper dedication of the shares, additional information <br />may be required prior to future SWSP approvals. <br />Depletions <br />The anticipated net depletions for this SWSP are 7.42 acre -feet per year. This SWSP <br />anticipates that a total of 1 acre of water surface will be exposed at the site in the dewatering <br />trenches around the Phase 1A & 1 mined area. You have provided a monthly breakdown of the <br />annual depletions that include 1.94 acre -feet of net evaporative loss, 2.94 acre -feet of water lost <br />with the mined product (which represents 200,000 tons of mined product), 1.38 acre -feet of <br />water used for dust control, and 1.16 acre -feet used for irrigation purposes. The material will be <br />mined below the water table in a dewatered state and will not be washed; therefore, in <br />accordance with the State Engineer's General Guidelines for SWSPs for Sand and Gravel Pits, <br />the assumed moisture content is 2% by weight. <br />Water will be used to irrigate approximately 1.0 acre of berms around the Phase 1A & 1 <br />area. For the purposes of this SWSP, you assumed that pasture grass will be the vegetation <br />planted on the berms. The State CU model was used with the Modified Blaney - Criddle method <br />and TR -21 crop coefficients to estimate the irrigation water requirement for pasture grass in this <br />area with the climate data taken from the Steamboat Springs weather station over the 1911 to <br />2010 period. The resulting average annual irrigation water requirement is approximately 1.16 <br />acre -feet per acre. For the 1.0 acre of berms, the total irrigation consumptive use is estimated to <br />equal 1.16 acre -feet per year (Table 3). <br />A stream depletion model was developed for the Steamboat Sand and Gravel Pit and <br />the effects of the delayed impacts are found on the attached Table 4. The aquifer <br />characteristics used in the model are transmissivity (T) = 48,000 gallons per day per foot (based <br />on the Yampa River basin's generalized transmissivity value determined in the June 2004 <br />Yampa River Basin Water Resource Planning Model prepared by Boyle Engineering <br />Corporation), specific yield (SY) = 0.13 (based on the Yampa River Basin Water Resource <br />%pF cO, <br />1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 F 303.866.2223 www.water.state.co.us <br />A J <br />