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soCOLORADO <br /> Division of Water Resources <br /> Department of Natural Resources <br /> February 9, 2022 <br /> J It T Consulting Inc. <br /> J.C. York, P.E. <br /> 305 Denver Avenue, Suite D <br /> Fort Lupton, Co 80621 <br /> Transmission via Email: icyork@i tconsultins?.com <br /> RE: SLURRY WALL LINER APPROVAL (PROVISIONAL) <br /> DERR PIT RESERVOIR (WDID 0303513) <br /> DERR PIT, DRMS M-2008-017 (WDID 0303035) <br /> NE1/4 SECTION 4, T5N, R65W <br /> WATER DIVISION 1, WATER DISTRICT 3, WELD COUNTY <br /> Dear Mr. York: <br /> The purpose of this letter is to provisionally approve the lining of the Derr Pit Reservoir. The Derr Pit Reservoir is <br /> primarily located in the NE1/4 of Section 4, Township 5 North, Range 65 West of the 6th P.M., and is part of the <br /> Derr Gravel Pit (DRMS M-2008-17). The Derr Pit Reservoir was lined with a soil bentonite slurry wall. The site is <br /> partially mined. The slurry wall liner leak test commenced on September 9, 2021 and concluded on December 31, <br /> 2021. A site inspection was performed by our office on October 26, 2021 to review site conditions and the leak <br /> test plan. <br /> Your report dated January 21, 2022 provides the liner summary and leak test results. The test data provided <br /> indicates that the liner meets the design standard referenced in the August 1999 State Engineer Guidelines for <br /> Lining Criteria for Gravel Pits(1999 SEO Guidelines). Meeting the design standard requires that during reservoir <br /> operations all water inflows and outflows for the liner perimeter enclosed area be accounted for on a monthly <br /> basis. <br /> This liner approval is applicable only during mining operations at the site and does not classify the structure as a <br /> reservoir capable of water storage. However, for the remainder of mining operations, water within the liner <br /> boundary is now classified as trapped native ground water. The trapped native ground water may be removed <br /> from within the lined area and returned to the stream system through surface flow or ground water recharge <br /> without the need for replacement so long as the operator does not put the water to beneficial use. All native <br /> trapped ground water remaining that is put to beneficial use (except for the water removed in product) must be <br /> replaced by the operator. All inflow of water into the liner boundary from any source, including precipitation and <br /> ground water inflows shall be removed by the pit operator so as not to cause out-of-priority storage. In order for <br /> the liner to be approved for water storage the operator must perform a final leak test once mining is complete <br /> and the site is at final grade. The final leak test will be allowed to have a modified duration of 45 to 60 days as <br /> long as the liner continues to satisfactorily operate during mining operations. <br /> Please contact me at 303-866-3581 x8246 if you have any questions. <br /> Sincerely, <br /> 4akaz"O'� <br /> loana Comaniciu, P.E. <br /> Water Resource Engineer <br /> Ec: Mark Simpson, District 3 Water Commissioner (Mark.Simpson@state.co.us) <br /> Louis Flink, Diversion Records Coordinator (Louis.Flink@state.co.us) <br /> WDID File (0303513 It 0303035) <br /> �4'opCO�oq <br /> 1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 v^w.colorado.gov/water <br /> Jared S. Polis, Governor I Dan Gibbs, Executive Director I Kevin G. Rein, State Engineer/Director * ? + <br /> *1876� <br />