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~ STAT~ OF COLORADO <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St.. Room 215 <br />Denver. CO 80203 <br />303 866-3567 <br />FA x: 303 632-8106 <br />OF COfp <br />~~~ 9,~ <br />Ne ,,, O <br />. 'r8~y t <br />~ r876 ~ <br />Ray Romer, <br />Govemar <br />Fred R. Banta, <br />Division Direttar <br />DATE: August 19, 1991 <br />T0: Carl Mount <br />FROM: Joe Dudash ~~ <br />RE: Lillylands Culvert Sizing <br />Permit No. C-91-078 <br />In a further review of the soil classification for the <br />application, it is questionable that a soil type of B <br />culvert sizing as submitted by Jim Stover. Soil types <br />evenly distributed over the permit area. This changes <br />calculations. <br />Lilly]ands permit <br />can be applied to the <br />B, C and D are somewhat <br />the culvert sizing <br />For CMP #5, a soil type D (Pinon loam) covers the drainage area (Soil <br />Classification Map No. 112). This changes the curve number from 79 to 89. <br />The runoff changes from .34 inches to .71 inches. Using Figure S-lA for <br />moderate slopes (7R-55) the peak flow becomes 15.3 CFS/in. instead of 13.0 <br />CFS/in. The adjusted peak flow increases from 2.7 CFS to 6.74 CFS. Using <br />Figure 4-28, page 189, of Handbook of Steel Drainage and Highway Construction <br />Products, the minimum culvert diameter is 19 inches, not the 18 inches <br />proposed. <br />For CMP ~8, a soil type of C (Progresso loam) equates to a curve number of 86, <br />a runoff of .56 inches, a peak flow of 20 CFS/in., an adjusted peak flow of <br />7.54 CFS and a culvert diameter of 20 inches. The proposed culvert diameter <br />is 18 inches. <br />I would suggest that you have Jim Stover justify his assertion that the soil <br />type is B (Page 9-24 of the Adequacy Review Responses, July 24, 1991) or <br />resubmit culvert sizing calculations using the appropriate soil types. <br />JJD/eke <br />7718E <br />