2012-01-04_HYDROLOGY - M2003016 - Laserfiche WebLink

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Mr. Joe Kraig Page 2 of 4 December 30, 2011 depletions that result from mining related exposure of ground water. The DRMS letter identified four approaches to satisfy this requirement. In accordance with approach nos. 1 and 3, you have obtained a bond for $1,050,152 through DRMS for lining or backfilling of the exposed ground water. Depletions You have estimated that 2.0 acres of ground water surface remains exposed at the Heit Pit in the settling ponds. Net evaporative depletions were calculated using a gross annual evaporation of 44 inches from the exposed water surface, with a credit of 9.05 inches for effective precipitation. The net depletion of ground water due to evaporation from the 2.0 acres of ground water exposed at the site was calculated to be 5.82 acre -feet. The settling pond water is used onsite for washing aggregate and dust control. The onsite production well, permit no. 66319 -F (WDID 0205038), will also be used for dust suppression and the washing of mined aggregate. You have estimated that a total of 1.0 acre - feet of ground water will be used for dust control purposes at the site during this plan period. You have projected washing up to 485,000 tons of mined aggregate a year. The annual consumptive use for aggregate washing was estimated at 10.7 acre -feet using a depletion factor of 3 percent by weight. There will be no concrete production at the Heit Pit during this plan period. The Glover method was used with to lag evaporative and operational depletions to the South Platte River. The following parameters were used in the model: transmissivity (T) = 140,000 gallons per day per foot, distance (X) from the surface of the exposed ground water to the river = 2,750 feet for evaporation losses and 3,000 feet for operational losses, distance (W) from the aquifer boundary through the exposed ground water to the river channel = 10,000 feet, and specific yield (SY) = 0.2. The location of the stream depletion is assumed to be perpendicular to the river. Lagged depletions for this plan period will total 17.42 acre -feet. Replacements The proposed source of replacement water for the Heit Pit is a total of 42.48 acre -feet of fully consumable effluent leased from the City and County of Broomfield ( "Broomfield "). Of this amount, 20.46 acre -feet will be used for replacement purposes under this SWSP. The lease was extended for a one -year period beginning September 1, 2011 and ending August 31, 2012. The replacement water will be released from Broomfield's wastewater treatment plant (WDID 0201021), which is located on Big Dry Creek approximately 29.75 miles upstream from the Heit Sand and Gravel Mine. Of the 20.46 acre -feet of leased replacement water from Broomfield, approximately 15% (3.04 acre -feet) will be lost during transit, based on a transit loss of 0.5% per mile for the 29.75 miles from the Broomfield wastewater treatment plant to the Heit Sand and Gravel Mine. The amount of Broomfield replacement water that reaches the Heit Sand and Gravel Mine is 17.42 acre -feet, sufficient to cover the projected lagged evaporative and operational depletions for this plan period. The monthly depletions and replacement deliveries are found on the attached Table 3. Conditions of Approval I hereby approve the proposed substitute water supply plan in accordance with §37 -90- 137(11), C.R.S., subject to the following conditions: