2014-10-14_PERMIT FILE - M2014043

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..0,% City of N 1� Thornton Infrastructure Maintenance Center 12450 Washington Street Thornton. CO 80241 -2405 October 8, 2014 Mr. Tyler O'Donnell Division of Reclamation, Mining and Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Frei Hatchery Pit - M.L.R.B. #M- 2014 -043 Dear Mr. O'Donnell: Infrastructure Department 720 - 977 -6600 FAX 720 - 977 -6202 www.cityofthornton.net OCT 14 7014 DIVISION OF RECLAMATION MINING AND SAFETY The purpose of this letter is to file an objection to the issuance of a Reclamation Permit on behalf of the City of Thornton (City) to the proposed mining and reclamation operation at the Hatchery Pit (Pit) located in parts of the NE '/4 SNW1 /4, SE1 /4 SW1 /4, SW1 /4 SW1 /4, and NW1 /4 NW1 /4 of Section 20, T -2 -S, R -67 -W, 6th PM, Adams County, Colorado. The City's North Dahlia Reservoir and Dam (a.k.a. Tigers Reservoir and Dam) are immediately adjacent to the proposed Pit. North Dahlia Reservoir has a capacity of 2,568 acre -feet and is a major component of the City's raw water infrastructure. The City's reservoir is also lined by a soil - bentonite barrier wall below the dam. The Bull Seep generally runs from south to north between North Dahlia Reservoir and the proposed Pit. The City has constructed an existing drain system to manage flows from the Bull Seep. The associated excavations with the proposed Pit appear to be within a reasonable proximity of the North Dahlia Dam. Currently the depth of the excavation, the location of the top of the excavation, and the slope of the excavation is unknown. This excavation could potentially adversely impact the stability of North Dahlia Dam or the soil - bentonite barrier wall below the dam. The City requests that the applicant perform an engineering evaluation to confirm that the proposed excavation will not adversely impact the dam or the soil - bentonite barrier wall below the dam. The analyses should include a drawing that defines the maximum western limit of excavation, the maximum depth of excavation, the temporary and final slope angle of excavation, and the calculations that demonstrate that the proposed Pit will not adversely impact the dam. The analyses need to be submitted to both Thornton and the State Engineer's Office (SEO), Dam Safety branch, for review and acceptance. The SEO needs to be involved because there will likely be excavations within 200 feet of a jurisdictional dam. S \OMMelanyon \Gravel Pits \Frei Fish Hatchery\DMG Letter Hatchery Pit do"