2017-04-26_HYDROLOGY - M2000041 (2)

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Mr. Mark McLean, P.E. April 20, 2017 Page 2 of 5 In accordance with the letter dated April 30, 2010 from the Colorado Division of Reclamation, Mining, and Safety ("DRMS"), all sand and gravel mining operators must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of ground water. According to the renewal request, the long term plan for the site is to construct reservoir liners adequate to prevent the infiltration of tributary ground water. According to the 112c Annual Report received by DRMS on June 4, 2015 (available from the DRMS website at the following link: http://drmsweblink.state.co.us/drmsweblink/0/doc/1070247/Electronic.aspx?searchid=630e0d15- 6426-4bea-a388-d4228679d6bc), Fremont Paving currently holds a bond in the amount of $2,095,000.00 for reclamation at the site. Please provide an explanation and/or documentation that the financial warranty in the amount $2,095,000.00 is sufficient to cover the cost of installing a clay liner or slurry wall that meets the Division of Water Resources requirements for preventing ground water exposure, in accordance with approach no. 3 of the April 30, 2010 letter from DRMS, with the next SWSP renewal request. Please provide explanation or documentation specific to this portion of the mine site, being Phase I-Parcel 4. Any future renewal request for this SWSP may not be approved if not submitted with the explanation and/or documentation requested above. DEPLETIONS Well permit no. 54064-F (WDID 1406561) was obtained to expose water in this pit. Depletions under this plan consist of evaporation from 3.5 acres of exposed ground water within Phase I-Parcel 4 of the mine site. The total of 3.5 acres of exposed ground water will result in 12.07 acre-feet of evaporative loss (see attached Table 1) under this SWSP. A Glover analysis was used to create unit response function ("URF") in order to determine the lagged depletions to the Arkansas River using the following parameters: • Transmissivity - 100,000 gallons/day/foot • Storage Coefficient - 0.20 • Distance to the Stream - 2,090 feet • Distance to No-Flow Boundary- 5,460 feet The resulting URF shown below was calculated by wrapping the last 5% of depletions into the first 16 months. Month 1 2 3 4 5 6 7 8 9 10 11 12 Fraction of 0.150 0.252 0.138 0.086 0.069 0.055 0.048 0.041 0.033 0.029 0.024 0.021 Pumping Month 13 14 15 16 17 18 , 19 20 21 22 23 24 Fraction of 0.017 0.014 0.012 0.011 Pumping