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ANdERSON CONSU~TINCI ENCIINEERS, INC. Civil Water Resources Environmental March 9, 2005 ~~"P;ES~E~ TR.- l MAC 10 2005 Mr. Thomas A. Schreiner piuision of Minerals & Geology State of Colorado Division of Minerals and Geology 1313 Sherman Street, Room 215 Denver, CO 80203 Re: Durham Pit Interim Flood Control Measure -Final Plan [ACE Project No. COVC03-Ol] Dear Tom: On behalf of the Varra Companies, Inc., Anderson Consulting Engineers, Inc. (ACE) is pleased to submit the attached Interim Flood Control Measure (Interim Measure) for the Durham Pit. As you are aware this Interim Flood Control Measure was required as part of the Division of Minerals and Geology (DMG) October 27, 2004 Findings of Fact, Conclusions of La~v and Order for the Vatra Companies, Inc. Mining Permit Amendment. The Interim Measure is required to minimize the impacts of floodwaters on the Objector's structures. It is our understanding that the Interim Measure is to be installed before the 2005 runoft7flood season and is considered a temporary measure that would remain in place until such time as the long term Flood Control Mitigation Plan is approved by the appropriate agencies. On February 16, 2005, at the DMG monthly board meeting, DMG suggested that the Interim Measure be in- placeprior tothe March board meeting. Ultimately, at the same meeting, the board approved a motion calling for completion of the Interim Measure by March 31, 2005. Immediately after the February board meeting, ACE presented the Objector with a concept design for placing a berm around the impacted buildings. Since February 16th, correspondence from the Objector's engineering consultant, Leaf Engineering, Ina, has centered around: a) numerous engineering questions regarding the hydraulic basis and design details for the berm; b) making the berm more of a permanent feature on the property; and c) utilizing legal counsel to draft an agreement which Varra Companies would be required to sign prior to construction of the berm. These issues have led Varra Companies to conclude that meeting the imposed deadlines for the Interim Measure might be in jeopardy. Since the beginning of January 2005, work has been progressing on the design of the long-term Flood Control Mitigation Plan. In late February, additional surveying information along the south side of the Durham Pit was received by ACE. By the beginning of March 2005 ACE had incorporated the surveying information into the existing condition hydraulics analysis to more accurately predict the 100-year floodplain along the south side of the Durham Pit. Varra Companies then requested that ACE consider the possibility of installing a temporary spillway to accommodate the Interim Measure. After reviewing the latest hydraulic information for the Durham Pit we are presenting the following plan to install a temporary spillway as the required Interim Measure. As shown in Attachment A, a spillway will be installed in a low area at the west end of the existing berm on the right bank ofthe Cache la Poudre River. The spilhvay will be approximately 47S feet long and installed at an average elevation of4922 feet. The spillway will allow a portion ofthe floodwaters in excess ofthe 10-year flood event to exit the main channel and be conveyed in the right overbank through the Durham Pit. Atypical 'I'?OPI:N`~CnccOJ-01ACOA'C03-0I TSchreiner Interim Aleas Crl-FINN_J~x 772 Whalers Way, Suite 200 • Fort Collins, CO. 80525 Phone: (970) 226-0120 • Fax: (970) 226-0121 • www.acewater.com