2021-06-01_HYDROLOGY - M2004051 - Laserfiche WebLink

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Aggregate Industries South Platte Combined SWSP June 1, 2021 Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, Et 6090 Page 16 of 23 the ditch that either uses an assumed maximum irrigation efficiency of 50% or a maximum irrigation efficiency that considers the site-specific potential efficiency and the effects of installation, management and maintenance of the irrigation system on the potential irrigation efficiency. In addition, the SWSP request must clearly define how the maximum irrigation efficiency was determined, including all assumptions and calculations. Furthermore, Aggregate is in the process of developing an augmentation station for the Zweck Et Turner Ditch. The applicant may not use the Zweck Et Turner Ditch as a replacement source in this SWSP until such time as all required measurement and bypass structures have been installed and approved by the water commissioner. Use of Excess Credits The Applicant has proposed to use excess replacement credit associated with their approved replacement sources in other gravel pit SWSPs approved pursuant to section 37-90-137(11), C.R.S., to the extent such excess replacement credit exists. The Applicant must provide written notice to the Division Engineer and Water Commissioner at least 30 days in advance of the desired commencement of use of the excess replacement credits, which must include the specific plan in which the credits will be used, the provision in the plan that allows an unnamed source to be added for credit, the annual and monthly amount of excess replacement credit available, the location at which the water will be delivered to the stream, and a copy of a lease agreement between the Applicant and the purchaser of the excess replacement credits if the additional plan is not owned by the Applicant. The Applicant cannot claim credit for the use of the excess replacement credits in any other plan until they have received written approval from the Division Engineer or Water Commissioner. In addition, for this plan period the Applicant requests the ability to lease excess replacement credits for use as a replacement source in the Stillwater Ski Lake SWSP (Plan ID 6024, WDID 0202850) requested pursuant to section 37-92-308(5), C.R.S. The Applicant has entered into a lease agreement to provide 16.9 acre-feet of excess replacement credits on the South Platte River above the St. Vrain confluence during the 2021 irrigation season. Dewateri ng All sites that are actively dewatering have been equipped with a Totalizing Flow Meter ("TFM") to measure the dewatering discharge. Monthly dewatering volumes must be recorded monthly with the meter readings included on submitted accounting. As long as dewatering operations remain continual at constant rates the net accretions are assumed to offset any lagged depletions. Under this assumption, the Applicant is not claiming any dewatering credit. Once dewatering operations stop, or are significantly reduced, at specific sites the monthly meter readings will be used to analyze post pumping depletions. The sites that will be actively dewatered during this SWSP period are the Wattenberg Pit, W.W. Farms Pit, Tull Pit, Tucson South Pit, and Irwin-Thomas Pit. Long Term Depletions and Reclamation 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 groundwater. The DRMS letter identifies four approaches to satisfy this requirement, which are identified and described in the attached letter.