2010-12-14_HYDROLOGY - M1999069 - Laserfiche WebLink

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Tom Hatton Page 2 December 9, 2010 If the information you are providing to DRMS is pursuant to approach no. 4, you will need to provide additional documentation to this office that specifies 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. This information must be provided to this office by April 30, 2011. If the requested information is not provided to the Division of Water Resources, any future SWSP may limit the mining operation so that additional ground water cannot be exposed, beyond that specified in this SWSP. Depletions The exposed ground water surface area is 2.6 acres resulting in 6.00 acre-feet of evaporative depletions. The aggregate production at the Wagner/Kauffman Pit #3 is projected to be 350,000 tons which will consume 10.3 acre-feet of water lost with the mined product. The total estimated net depletions for 2011 from this operation will be 16.3 acre-feet per year. The mining operation has continuously dewatered directly back to the Big Thompson River since 2000. The estimated dewatering rate at the Wagner/Kauffman Pit #3 site is approximately 1000 gallons per minute. As long as the pit is continuously dewatered, the water returned to the stream system should be adequate to offset the depletions. Once dewatering at the site ceases the delayed depletions must be addressed. A stream depletion model was used to determine the timing of lagged depletions to the Big Thompson River. The following parameters were used in the stream depletion model: transmissivity (T) = 50,000 gallons per day per foot, specific yield (SY) = 0.2 (which is typical for an alluvial aquifer), the distance of the exposed ground water to the river = 200 feet, and the location of the parallel impermeable boundary was estimated to be 3,500 feet from the stream. Based on the above factors, the lagged stream depletions for the term of this SWSP were estimated to be 16.3 acre-feet as shown on the attached Table 3. According to the Applicant, the distance from the surface of the exposed ground water area to the Big Thompson River was measured based on the down gradient extent of the exposed ground water surface (nearest point). For purposes of this SWSP, the method used to measure the distance to estimate the lagged depletions will be accepted, however any future SWSP must measure the distance from the exposed ground water surface area to the Big Thompson River based on the centroid of the exposed ground water surface. Replacements Replacement water for this pit will continue to be made available throughout the year from a lease of 65 acre-feet of fully consumable water from the City of Loveland ("Loveland"). This lease also applies to losses at another gravel pit, Kauffman Pit DRMS M 78-327. A copy of the lease associated with the mining operation was provided to the State Engineer's Office with the plan request and a copy of the lease is attached to this letter. The duration of the lease is from January 1, 2010 through December 31, 2012. A 4 percent transit loss from Green Ridge Glade Reservoir to Wagner/Kauffman Pit No. 3 has been applied to the delivery of the replacement water. Under the terms of the lease, replacements can be made using a variety of water owned by Lovelandtincluding, but not limited to, Windy Gap reusable effluent, Loveland Storage Reservoir water