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STATE OF COLOR4D0 piC Hna AMM, Gavem or <br />DEPARTMENT OF NATURAL RESOURCE III III III III IIII III <br />Harms D. Sherman. Executive Drr actor <br />NIINEU LAND RECLAA~IATION 999 <br />723 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 60203 Tel. (303) 8923567 <br />Hamlet J. Barry, III, <br />Director <br />March 27, 1980 <br />TO: Todd Gibson <br />FROM: Jim Pendleton t <br />RE: The Revi d Design d Construction for Retention Dam #1 at the <br />Red Can rte near Cedar Edge, Delta County, Colorado <br />I have reviewed the design report and letter of revision submitted for <br />Grand Mesa Coal Company by F. M. Fox and Associates, Inc. I recommend <br />that you require the applicant to proceed as follows: <br />1) The foundation site beneath dam #1 should be drilled to ascertain <br />whether any voids equivalent to the one encountered beneath the originally <br />proposed dam #3 exist. Angering along the dam centerline on 50 foot <br />intervals to depths of 25 feet should suffice. <br />2) The "sliding wedge" analysis referenced on page S of t_he F. M. Fox <br />design report dated December 3, 1979 should be repeated for the revised <br />configuration of dam #3. <br />3) Piezometers should be installed at the locations originally stipulated <br />for the installation of the relief wells in the F. M. Fox design report. One <br />and one-half inch perforated plastic pipe installed in gravel packed six <br />inch angered holes should suffice. Monitoring of these wells should be <br />performed monthly in order to determine the occurrence of potentially <br />detrimental saturation of the foundation and/or embankment materials. <br />4) In accordance with Section 715.17 (e)(7) of the Federal Interim <br />Regulations, the construction of the dam shall be "inspected under the <br />supervision of, and certified after construction by a registered professional <br />engineer". Preferably, this inspection and certification should be done <br />by F. M. Fox and Associates, Znc., who designed the structure. <br />Conformance with these requirements should result in the construction of <br />a stable dam embankment. <br />Jim <br />