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_; • • <br />August 10, 2000 <br />Mr. Erich J. Bower <br />Environmental Engineer <br />Climax Molybdenum Company <br />Henderson Mill <br />19302 County Road <br />Parshall, Colorado 80468 <br />Subject: Response to Technical Revision No. 9, Stipulation No. 4 Tailing Dam No. 3 <br />Decant Grouting, Henderson Mill, near Parshall, Colorado <br />Project No. 6800044400.00-9407 (T-G2000) <br />Dear Erich: <br />We have prepared this letter in response to Technical Revision No. 9 (TR-09), Stipulation No. 4 <br />prepared by the State of Colorado Divisions of Minerals and Geology (DMG) dated Apcil 21, <br />2000. Presented below is a summary of the request, a brief project history and a brief discussion <br />of our opinion. <br />SUMMARY OF REQUEST <br />We were requested by the Climax Molybdenum Company (Climax) to prepare a response to a <br />letter received from DMG. The DMG letter provides Climax conditional approval for grouting <br />the existing decant structure closed and is designated as Technical Revision No. 9 (TR-09) to <br />Permit No. M-77-342. Conditional approval was given provided that four stipulations are met. <br />We have been requested to provide a response to Stipulation No. 4, which reads as follows: <br />The penetration of No. 3-Dam by the abandoned No. 2-Dam decant system could create a <br />pathway for seepage and piping which are potential dam stability issues. Within 60 days <br />of dale of technical revision TR-09 approval, He~tderson must provide the Di~~isiw7 with a <br />report on this po[enGal, which may comprise records on the construction of No. 3-Dam <br />as they relate [o the decant system penetrations, or if adequate historical records are <br />unavailable Henderson mast provide the Division with a proposal to iin~estigate the <br />nature and cortdiliw7 of the decant system penetrations <br />PROJECT HISTORY <br />Construction of the Henderson tailing dams began in the early 1970's. Two dams were <br />constructed and are referred to as the Lower and Upper Tailing dam or Tailing Dam No. 1 and <br />No. 2, respectively. Both dams are constructed using the upstream method of Tailing <br />deposition. <br />J:1VvPM45TER WROJEOTS14C400Je< dac Ofl~1d00~3 31 PM) <br />