Laserfiche WebLink
' NOV-06-'6? 15:57 1D:C0 NINED LRIJD REC'L TEL N0:303-632-610b #463 P04 <br /> <br />' Mr. Gordon Morgan <br />-3- <br />November 7, 1989 <br /> F <br />d t <br />d W <br /> osy an <br />(y <br />ro <br />ater quality (continued) <br /> 72. Please provide a detailed explanation of the plan to fill 1n the Area One <br />' slide inundation area. If you do not wish to pump out the watet• and remove <br /> the existing silt, then we xould recommend installation of a grainular filter <br /> layer, 6 to 9 inches thick, placed directly on top Of the existing sediment <br />' deposit, followed -aith the pond being slowly filled with rock to the proposed <br /> channel design configuration. We also recommend you obtain all necessary <br /> approvals for fill placement/effluent discharging operations frC~m.both the <br /> ~ U.S. Arnly Corps of Engineers and the Nater Quality Control Di via•ion of the <br />' Colorado Department of Health. <br /> 13. Please provide channel designs (cross-section size and shape, maximum <br />velocity at design conditions, channel bottom particle size) for the <br /> filled-in area of inundation above the Area One slide, the toe of the Area <br /> Three slide and the toe of the Area Four slide. Please include construction <br />' methods and materials. <br /> 14. Please commit to submitting the design for the silt-retention facility <br /> referenced on page 12 of the Access Road CAP, the contributing watershed <br />' area survey, and the design parameters and methodologies used in the <br /> analysis. These parameters should include the USLE-derived sediment volume, <br /> 40-micron particle Size settling vetoclliy, the 10-year, 24-hour storm runoff <br />' volume, and the 100-year design storm emergency spillway discharge. Please <br /> also include in the final designs all structure dimensions, calculations, <br /> maps, figures and references end other supporting documentation. Design <br />' information should be submitted 60 days ahead of construction to allow the <br /> pivision adequate time for review end response. <br /> 15. Please provide the design and location of the silt-retention factllty access <br />' road. <br /> Slop e Stability <br />' <br /> 16, Please commit to a 3:1 or gentler slope from the base of the fill et the <br /> Area One slide to stetson 3+26.6 (Area One/Area Four cross section). Areas <br />' upslope of station 3+26.6 can be graded to 2:1. <br /> <br />17. ^ <br />Please commit to either cutting or filling the slopes at the Area Two and <br />' Area Three slides to achieve a 2:1 final slope configuration. This is <br />recommended 1n light of the CTL/Thompson Report that concludes that the <br /> maximum slopes at Areas One through Four should not exceed 2:1. Methods <br /> proposed to conduct this grading, as well as cross sections documenting <br />' current and post-grading topography, should be submitted to the Division <br /> for review, <br />' 18. from the cross section provided, it appears that the proposed removal of <br />material at the Area Four slide to form a 2:1 slope will occur only at the <br />upper portion of the fill. Please commit to grading the steep slopes near <br />' stations 2+86.6 and 3+10.1 so es to achieve a slope no steeper than 2:1. <br />Please commit to grading the lowermost portion of the fill, from station <br />3+10.1 to station 3+33.5, to a slope no steeper than 3:1. <br />