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Timothy and Jeanne Iverson <br /> 5011 F Street <br /> Greeley CO 80631 <br /> June 21,2018 <br /> Mr. Peter S. Hays <br /> Environmental Protection specialist RECEIVED <br /> Division of Reclamation Mining and Safety <br /> 1313 Sherman Street Room 215 JUN <br /> Denver, CO 80203 M10N OF RECLAMATION <br /> Re: Iverson Mine Reclamation <br /> 112c Permit,File No.M-2011-001 <br /> Water Division 1,Water District 3 <br /> Weld County,Colorado <br /> Evaluation of Reclamation Improvements <br /> Dear Mr. Hays: <br /> TZA Water Engineers was retained to evaluate the reclamation improvements at the Iverson Mine. The <br /> evaluation addressed my concerns that the reclamation improvements are not constructed correctly and <br /> are not adequate to survive future floods. Attached is the evaluation report and the technical support <br /> data. The conclusions and recommendations of the evaluation are summarized below: <br /> TZA CONCLUSIONS AND RECOMMENDATIONS <br /> The probability is high that the riverside berm surrounding the reclamation area will be overtopped and <br /> breached during flood events greater than the 2-Year Flood. The high probability is based on the narrow <br /> width of the riverside berm,minimal freeboard, lack of erosion protection and inadequate spillways to <br /> reduce differential heads. Previous breaches of the riverside berm resulted in significant damages to the <br /> site including severe erosion of banks, sediment deposition in the lake and washout of the spillway <br /> structures. Similar damages are possible if the berm is breached in the future. The detrimental impacts <br /> of mining pit capture by a river are well documented(See USBR Rehabilitation of Floodplain Mining <br /> Pits: Interim Report Detailing Initial Plans and Procedures 2005). <br /> TZA Water Engineers recommend the following improvements be made to stabilize the site and prevent <br /> breaching of the riverside berm during future flood events. <br /> 1. The low area in the riverside berm located at the northwest corner of the lake should be <br /> uniformly graded to elevation 4686.0 feet which is approximately equal to the pre-mining <br /> elevation and is above the 2-Year Flood elevation of 4685.3 feet. <br /> 2. The riverside berm should be protected with riprap on both the riverbank and pitside for the <br /> critical section of the berm extending from the inlet spillway approximately 3,200 feet around <br />