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<br />Method of Calculation: Table 111-1 (100~year frequency storm- <br /> <br />proJlosed land use) <br />Column 1: A rainfall interval of 10 minutes and a total time oC G <br /> <br />hours were selected. <br /> <br />Column 2: <br /> <br />These valucs were taken Crom the RainCal1 DCJlth~Duration- <br /> <br />Frequency Graph. <br /> <br />Column 3: <br /> <br />The incremental precipitation was determined hy Column 2 <br /> <br />(20 minutes] minus Column 2 (10 minutes) etc, <br /> <br />Colunm 4: <br /> <br />Incremental precipi tati,)n amounts from Col unm 3 were re- <br /> <br />arranged into a realistic storm hydrograph pattern. <br /> <br />Colunm 5: <br /> <br />A constiJnt maXImum infiltration rate of one"hn1C inch per <br /> <br />hour was used as discussed previou~;ly. <br /> <br />Column G: <br /> <br />The total detention and depression storage is detenni ned Crom <br /> <br />Tahle 2-2 of the Criteria Manual aDd shown as a total at the hot tom uC <br /> <br />Colunm G. <br /> <br />For each time period the detention and depression storage in <br /> <br />Col umil G is found by subtracting iDfi 1 tration, Column 5, Crom precipi tn, <br /> <br />tion, Column 4. <br /> <br />If the result is Ilegat:.L\le, there is no excess Cor this <br /> <br />period, and Column G and Column "7 and zero. <br /> <br />If the result is positive, <br /> <br />the amount is entered In Column G as tlw detenti.on and clepi'esc ion stor:lge <br /> <br />for the time period. <br /> <br />When the cumulativc amount in Column G equals the <br /> <br />total shown at the bottom of the COlU1l111, the detention storage is Cully <br /> <br />used and all remaining values arc zero. *Note that the last V:l111C' oC <br /> <br />detention storage is less thun Column '!minus C:olullll1 5 and wa~; detel"lllinC'd <br /> <br />by the difference between tbe total amount and the amount accumulated <br /> <br />-27 <br />