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EUGENE M. SHEARER,P.E. <br />CONSULTING GEOLOGIST <br />5720 South Jasmine Street <br />Englewood,CO 80111-1525 <br />(303) 771-2371 <br />Mr. Bryan Archer <br />Sun Coal Company <br />10200 West 4th Ave., Suite 120 Ref:Yampa River Sedimenta- <br />Wheat Ridge, Colorado 80033 tion Pond Emergency <br />Soillwa.v "As Built" <br />Dear Bryan: <br />The Yampa River Sedimentation Pond Emergency Spillway <br />installation was completed on SMay92. Prior to discussing <br />the "as built" characteristics of the structure it may be <br />helpful to very briefly review the events preceding final <br />construction. <br />September 1991- Discussion regarding the new regulation that <br />requires a separate emergency spillway on <br />sedimentation ponds. <br />3 October 1991- Submittal of a spillway design based on file <br />data without benefit of field measurements. <br />5 November 1991- Acceptance of the spillway design by MLRD, <br />except for outflow design consideration. <br />18 December 1991- Submittal of generalized outflow design <br />specifications and calculations governing <br />overall spillway and outflow design. <br />24 April 1992 -Stake emergency spillway. <br />5 May 1992 -Survey the installed emergency spillway and <br />outflow for compliance with approved design <br />specifications. <br />The Emergency Spillway "As Built" Yampa River Sedimentation <br />Pond drawing that accompanies this report sets forth the <br />measurements of the completed spillway. Cross-section A-A' <br />indicates that when the water level during the 24 hour 100 <br />year event reaches the design maximum depth of one foot, the <br />freeboard will be one Foot, as required by Section <br />4.05.6(11)(e), Regulations of the Mined Land Reclamation <br />Board. <br />The spillway grade to the point of outflow is 4.55q, and the <br />plus or minus 0.5 foot riprap and plus or minus 0.1 gravel <br />spillway liner should adequately resist erosion from water <br />flow. The flagstone or sandstone riprap includes some large <br />slabs that measure one to two feet in length and width, <br />however the thickness is approximately 0.5 Yoot. Although <br />the design required riprap to cover the area four feet up <br />the spillway slope from the centerline, surplus flagstone <br />