2012-08-20_HYDROLOGY - M2008078 - Laserfiche WebLink

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Michelle Hatcher Page 2 August 20, 2012 results in an annual evaporative Toss of 2.5 acre -feet, which is based on the decreed evaporation rate in Case No. 2002CW181 for gravel pits near Lamar. Operational uses of groundwater include water retained in the mined material that is removed from the gravel pit site and water used to control dust on haul roads and stockpiles at the West Farm Pit. You have estimated the total annual amount of material to be mined as 750,000 tons, at 4% moisture content, which equals a consumptive use value of 22.1 acre -feet. You have also estimated the amount of groundwater to be used for onsite dust control, which is considered to be 100% consumptive, as 6.2 acre -feet annually. The total operational consumptive use at the site would be 28.3 acre -feet. The total on -site evaporation and operational depletions would be 30.8 acre -feet. Lagged depletions to the Arkansas River were calculated by using the AWAS model, and an interpolated stream depletion factor of 88 days ( "Stream Depletion Factors, Arkansas River Valley, Southeastern Colorado" by C.T. Jenkins and O. James Taylor; USGS OFR 72- 192). A summary of the lagged monthly stream depletions is shown in the attached revised Table 3. No groundwater will be used for equipment washing, concrete production, reclamation or any other purpose. Total monthly depletions for each use will be limited to the totals provided in your Table 2. No groundwater was exposed within the permit boundary prior to January 1, 1981. No phreatophyte credit has been applied to this plan. Replacement The proposed source of replacement water is GP Aggregates' ownership of 284 common shares in the Lower Arkansas Water Management Association ( "LAWMA "). Only 38 LAWMA shares will be dedicated to this plan. This water will cover depletions throughout the entire year. A transit Toss will be accounted for by LAWMA as part of their agreement with GP Aggregates. LAWMA anticipates one share to yield 0.85 acre -feet. Depletions totals will be provided by GP Aggregates to LAWMA, which will make replacement deliveries to the Arkansas River using fully consumable water. Revised Table 3 shows the proposed replacement schedule, the number of shares used and the net river balance. A copy of the signed agreement for the 2012 through 2013 period between GP Aggregates and LAWMA for the administration and accounting of the replacement water was provided to this office with the SWSP request and is attached to this letter. After mining and reclamation is complete, the applicant will construct a lined reservoir with a total surface area of approximately 183 acres. In accordance with the letter dated April 30, 2010 (copy attached) 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. In accordance with approach nos. 1 and 3, you have indicated that a bond has been obtained for $88.802 through the Division of Reclamation, Mining, and Safety ( "DRMS "). This bond is for reclamation requirements under the current permit but may not be sufficient for lining or backfilling the pit to ensure that depletions from groundwater evaporation do not occur in the unforeseen event, or events, that would lead to the abandonment of the Pit. Future SWSPs for this site will not authorize any additional use of ground water until the Applicant provides documentation that a bond sufficient to cover lining or backfilling of the pit has been obtained.