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_ ~ ~~ STATE OF COLORADO DEPARTMENT Of NIGNWAYS ~eaa ~ D17~1IC~ 11 't~ ~~t 405 Eria - P.O. Box 536 `~~ .-~~`{ PueOlo. Colorado 81002 ••?•~~~:./~'^'p~ 130.7) 5~~-8286 ~„~o-J• April 28, 1987 Mr. Bill Bisers~art, General l~nager Valco, Inc. P.O. Box 591 Lamar, CO 81052 Dear Mr. Eiserlmen: We have evaluated yaa latest proposal to continue Wining in the prktlnaea River, sa presented to us on April 3, 1987 and described in your Secl.ion 404 Permit Application, 00-0YT-0501. We object to that proposal and to the continuation of mining adjacent to the bridges on State Highway 50, Past as well as ctiu7:ent mining practices at this locatim present a high risk to the bridges at both moderate and large flood flows. 'ibis is unacceptable. Had We been given an opportunity to cent on previous applications filed with the Mined lard Reclamation Board or the U.3. Ar>~y Corps of Engineers, we would have strenuously objected to ar>,y mining Which would encroach into the charutel beyond the existing bridge abutments. We have discussed this concern with you en several occasions, std this remains a serious concern. We also believe that the proposed realignment of the p~rese~t river chhenrtel significantly increases risk to the bridges. Your plan does not adequately mitigate that risk for the following reasons: 1. The top elevation of 3608 for the rubble Dore is too high and should be lowered. 2. The bottom elevation of 3598 is not low enough to prevent unde~;~;*~ during en overtopping flow. Qa experier-ce indicated that plunge pool erosion may occla' down to elevation 3580 or even lower. 3. No means were provided to mitigate hesdcutting from the ends Df the rabble core. 4. the proposed car>ICrete rubble core held together with cement slurry would not form a moralithic mBas using normal canstnvetion praeti~xa. We believe that the ca>,crete chunks will break loose causing core failure during an overtopping flaw. 5. hoed distributions of the forces an the rubble core Were not provided to checlr for overturning.