2021-10-19_HYDROLOGY - M2001085 (2)

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COLORADO 4 Division of Water Resources Department of Naturai Resources October 19, 2021 Craig M. Lis, Principal Engineer Martin and Wood Water Consultants, Inc. 538 Commons Drive Golden, CO 80401 Re: GSL Sand and Gravel Substitute Water Supply Plan (WDID 0202584) (a.k.a. 120th Estates Partners Sand and Gravel Mine and 124th Estates Pit) GSL Sand and Gravel Mine, DRMS Permit No. M-2001-085 (WDID 0203018) Section 35, T1 S, R67W, 6th P.M. Water Division 1, Water District 2, Adams County SWSP ID: 4558 Approval Period: November 1, 2021 through October 31, 2022 Contact information for Mr. Craig Lis: 303-526-2600 and clis@martinandwood.com Dear Craig M. Lis: We have reviewed your letter dated September 15, 2021 requesting renewal of the above- referenced substitute water supply plan ("SWSP") to cover depletions caused by the GSL Sand and Gravel mine in accordance with section 37-90-137(11), C.R.S. The original plan was approved on May 20, 2002, and its renewal was most recently approved in a letter dated April 5, 2021. That plan was valid through October 31, 2021. The required fee of$257 for this renewal of the SWSP has been submitted (receipt number 10015416). Plan Operation This SWSP covers depletions caused by sand and gravel mining operations at the GSL Sand and Gravel Mine ("Applicant"). Mining operations were completed in November 2011 and the pit filled, creating a 26.70-acre pond. A slurry wall was installed around the pond however the liner is not functional, therefore the Applicant requested an amendment to the mining permit to the Division of Reclamation Mining and Safety ("DRMS") to allow for backfilling of the pit. Since February 2012 when the exposed surface area was 26.7 acres, the Applicant was working on backfilling the pond and currently the exposed groundwater surface area as of September 2020 is 0.90 acres. Depletions The depletions that result from the past mining operation at the site consist of evaporation from exposed surface area, water used for dust suppression, water removed in the mined product, and depletions from dewatering and the filling of the pit once dewatering ceased. Other than evaporation from the exposed groundwater surface, no new depletions will occur during this SWSP approval period. All historic water use remains in the lagging analysis in order to account for any depletion still impacting the river. Prior to November 2011, the total exposed surface area at this site was 1 acre. Starting in November 2011, the operator allowed the pit to fill as mining operations were complete. The Applicant had estimated that the pit would fill with groundwater to an equilibrium state within three months. The pit filled to create an exposed groundwater surface area of 26.7 acres by February 2012. Beginning Off'C01Q�1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 www.colorado.gov/water ew— Jared S. Polis, Governor I Dan Gibbs, Executive Director I Kevin G. Rein, State Engineer/Director I y 'f 1876{`