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DOWNDRAIN ANALYSIS <br />Note: <br />1) Runoff 00 -Year storm event from Preliminary Closure and PostClosure Maintenance Plan prepared by Shaw Environmental, Inc., January 2010. <br />2) Allowable headwater estimated from details in the Preliminary Closure and PostClosure Maintenance Plan drawings prepared by Shaw Environmental, Inc., January 2010. <br />Page 3 of 3 <br />Calculated Runoff <br />Design Downdrain Dimensions <br />Allowable <br />Max Discharge <br />100-Year(l) <br />1000 -Year <br />Diameter <br />Number of <br />Slope <br />Headwater (2) <br />Inlet <br />Barrel <br />Downdrain <br />(cfs) <br />(cfs) <br />(in) <br />Barrels <br />(ft/ft) <br />(ft) <br />(cfs) <br />(cfs) <br />Notes <br />DD5 <br />8.0 <br />9.0 <br />18 <br />1 <br />0.0500 <br />3.50 <br />15.3 <br />12.7 <br />Downdrain capacity is sufficient. <br />22.6 <br />28.8 <br />24 <br />1 <br />0.0500 <br />4.00 <br />29.1 <br />27.4 <br />Downdrain capacity is insufficient through <br />barrel. <br />36.2 <br />45.7 <br />30 <br />1 <br />0.0500 <br />4.50 <br />56.7 <br />49.7 <br />Downdrain capacity is sufficient. <br />DD6 <br />11.1 <br />12.8 <br />18 <br />1 <br />0.0500 <br />3.50 <br />15.3 <br />12.7 <br />Downdrain capacity is insufficient through <br />barrel. <br />28.7 <br />38.5 <br />24 <br />1 <br />0.0500 <br />4.00 <br />29.1 <br />27.4 <br />Downdrain capacity is insufficient at inlet <br />and through barrel. <br />48.4 <br />62.4 <br />30 <br />1 <br />0.0500 <br />4.50 <br />56.7 <br />49.7 <br />Downdrain capacity is insufficient at inlet <br />and through barrel. <br />DD7 <br />14.7 <br />17.3 <br />24 <br />1 <br />0.0500 <br />4.00 <br />29.1 <br />27.4 <br />Downdrain capacity is sufficient. <br />Note: <br />1) Runoff 00 -Year storm event from Preliminary Closure and PostClosure Maintenance Plan prepared by Shaw Environmental, Inc., January 2010. <br />2) Allowable headwater estimated from details in the Preliminary Closure and PostClosure Maintenance Plan drawings prepared by Shaw Environmental, Inc., January 2010. <br />Page 3 of 3 <br />