2013-04-16_HYDROLOGY - M1981058 - Laserfiche WebLink

Home Browse Search

Mr. Mark A. McLean, P.E. DeBeque Pit SWSP is contiguous with the added pond area. After mining operations are completed, the site will be reclaimed as an unlined ground water pond with a surface area not to exceed 11.6 acres and with a net depletion of 27.62 acre -feet during the April through October call period. The proposed sources of replacement water for this pit are 40.7 acre -feet of historical net stream depletions during April through October from the dry- up of 19.1 acres of land historically irrigated lands with 6.1 shares of the Larkin Irrigation Company ( "Larkin Ditch ") and a dewatering credit of 67 acre -feet per year. The post mining depletions will also be covered by the dedication of the 6.1 shares in the Larkin Ditch. 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. The DRMS letter identifies four approaches to satisfy this requirement. The 4 approach requires documentation to identify what water rights or other permanent water source will be dedicated to the SWSP to assure that all permanent depletions from either an unforeseen abandonment of the site by the Applicant or as a result of long term ground water exposure after completion of mining and reclamation will be replaced so as to prevent injury to other water rights In accordance with approach no. 4, you have provided an affidavit dated December 21, 2011 that dedicates 6.1 shares of Larkin Ditch water (2 shares were already dedicated to this pit in the augmentation plan approved in case no. 2005CW076 and an additional 4.1 shares of Larkin Ditch are dedicated as replacement water solely for this SWSP) for as long as there are depletions at this gravel pit site or until such time as another replacement source is obtained. A copy of the affidavit is attached to this letter. For the purposes of this SWSP, this affidavit will be accepted for the dedication of the shares; however, if the State Engineer determines that a different affidavit or dedication process is necessary to assure proper dedication of the shares, additional information may be required prior to future SWSP approvals. Depletions April 12, 2013 Page 2 The anticipated net depletions for this plan are 159.13 acre -feet per year. The exposed ground water area during the plan period will vary from 5.6 acres during active dewatering (based on 3.6 acres of the existing pond and not more than 2 acres exposed in the dewatering trenches) to 9.7 acres when the dewatering system is shut off. According to the information submitted, no water surface was exposed within the reclamation permit boundary prior to January 1, 1981. You have provided a monthly breakdown of the annual depletions made up of 21.15 acre -feet of evaporative loss, 1.5 acre -feet of water used and consumed for dust control, and 5.88 acre -feet of water lost with the mined product (which represents 200,000 tons of mined product per year). A phreatophyte credit of 3.4 acre -feet has been applied to this plan, reducing the evaporative loss to 17.75 acre -feet per year. The attached Table 2 depicts the projected consumptive use including evaporation losses and operational losses. The IDS AWAS stream depletion model was used to determine the lagged depletions to the Colorado River. The aquifer characteristics used in the model are based on the lagging parameters decreed in Case No. 2005CW76 and they are: transmissivity (T) = 50,880 gallons per day per foot and specific yield (SY) = 0.2, the distance of the exposed ground water to the stream =150 feet, and the location of the parallel impermeable boundary was estimated to be 2,000 feet from the stream. The lagged stream depletions for the period of this SWSP are estimated at 158.73 acre -feet for the period 4