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~, <br />~` . <br />BRUCE F. ERICKSON, P.E. <br />2138 Illinois Court <br />Loveland, Colorado 80538 <br />(Phone) 970593-0353 <br />(Cell) 970-290-8333 <br />May 17, 2006 <br />Mr. Chris Varra <br />Varra Companies <br />8120 Gage Street <br />Frederick, CO 80516 <br />R€: DURHAM PIT -FLOOD CONTROL MITIGATION PLAN <br />PERMIT NO. M-1978-058 <br />Chris: <br />As requested by the Colorado Division of Mineral and Geology, I prepared an <br />Opinion of Probable Construction Costs for the proposed flood mitigation and <br />mine reclamation construction as proposed in the Construction Plans prepared <br />by Anderson Consulting Engineers, Inc. Enclosed is a copy of the opinion of <br />Probable Construction Costs. <br />The estimate is based on maintaining the existing river bank adjacent to the <br />concrete weir control wall between plans river stations 2+50 to 14+00. Arxording <br />to the stops and bank stability analysis tests and report by CGRS, Inc., the <br />existing river banks are stable and will maintain the stability during flood event <br />simulations. This stability is evidenced by the decades the existing bank with <br />vegetation has functioned without degradation. The concrete control wall allows <br />river flows exceeding the 10-year event to be conveyed through the mine <br />property. <br />The river bank armoring design and plans from river reach station 2+50 to 14+00 <br />was designed and shown on the plans prior to the bank stability analysis <br />investigation and report. The stability analysis report requires this plan to be <br />altered since to excavate the existing vegetation and bank material for the <br />installation of the buried rip rap would jeopardize the existing bank stability. Rip <br />rap will now be limited to the west and east ends of the concrete control wall <br />