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Memo <br />April 8, 2010 <br />To: Travis Marshal <br />From: Berhan Keffelew <br />Re: Moors Pit storm water pond sizing evaluation. <br />As you requested I have evaluated the pond sizing for the above pit labeled "OS-1 and "OS 2". <br />The operator had utilized the TR-555 method for a 2 year 24 hour event for the area,(.70 inches) which I <br />assumed is what the Division requested. Total water shed acres is 38.8 acres. Since there appears to be <br />no set ppt events that the CDOH&E requires for BMPS, it is acceptable. <br />Input Parameters utilized for Hyd. No. 1 & 2 <br />Sheet Flow <br />A <br />Manning's N value =0.350 ? 035 =035 <br />Flow length (ft) = 300.0 =300 <br />Two Year 24 hr ppt.(in) =.070 =0.70 <br />Land Slope = 43.33 =13.0 <br />Shallow Concentrated Flow <br />Flow length (ft) =3096 =1762 <br />Water course slope (%0 =17.80 =11.40 <br />Surface description = unpaved =unpaved <br />Average velocity (ft/s) =6.81 =5.45 <br />Channel Flow <br />X sectional flow area(sqft) =21.60 =21.60 <br />Wetted perimeter (ft) =21.97 =21.97 <br />Channel slope (%) =9.70 =9.7 <br />Manning's N value =0.045 =.0.045 <br />Velocity (ft/s) =10.20 =10.20 <br />Flow length (ft) =4545.0 =2879.0 <br />The 0.35 (n value listed in TR-55 TC work sheet was a typo, it should be .0.035, as listed in the table <br />values (Table F 1c)