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Orange Grove <br /> Storm Water Plan Page 2 <br /> 06C I.S. total for 12 lots 61,056 S.F. <br /> I.S. total for road 26,640 S.F. <br /> I.S. TOTAL FOR SUBDIVISION 87,696 S.F. <br /> Total Impervious Surfaces allowed at 12% = 184,782 S.F. <br /> *The total build-out will only result in use of 47Z of allotted impervious <br /> surface coverage. <br /> RUNOFF VOLUME ESTIMATES: <br /> The first JO of rainfall will generate a volume of 3683 cu. ft. of storm water <br /> from the total impervious surfaces. (Total I.S. X .042') <br /> (A) Road ditch/swale effective retention within R/Ws;2 (6') effective width of <br /> 13' design width X I" depth control height with gradient = 17,760 S.F. X <br /> .084° = 1492 cu. ft. <br /> (B) ..Two grassed swales as easements along lots 19 and 22;(2) 12' X (420' t 570'); <br /> 5.5' effective width X 990' length = 5445; 5445 x .5" depth (.042) = 229 cu. ft. <br /> (C) Two 50' X 12° x 6 ' retention ponds; 3600 cu. ft. X 2 = 7200. cu. ft. <br /> CONCLUSIONS: <br /> - Total constructed infiltration = 1721 cu. ft. rainfall; <br /> -- Total constructed retention = 7200 cu. ft. rainfall; <br /> - 46% of " rainfall will percolate naturally into soil along man-made devices; <br /> - 195% of the and almost a full .1" of rainfall could be retained in the swale/ <br /> pond system. The extra freeboard is needed due to often neglected yearly maintenance./ <br /> cleanout schedules. <br />