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f G • ,._� • 141 <br />TO: Gordon Witcher <br />FROM: Jane Zimmerman <br />DATE: September 13, 1991 <br />SUBJECT: McCauley Construction Drainage <br />Calculations <br />`The submitted calculations do not show that the swale will <br />not be backed up deeper than 0.5' for the 2 year, 24-hour <br />storm which is the criteria that has been given for allowing <br />detention in the swale. However, I was able to generate the <br />2 year, 24-hour storm hydrograph using the Santa Barbara <br />Urban Hydrograph (SBUH) method and determined that the peak <br />flow from the storm would be less than the flow out of the <br />orifice at a head of 0.51. Using the simplified rational <br />method of determining detention volume, it can be assumed <br />that no detention will occur in the swale during the 2 year, <br />24-hour storm. It is my conclusion that the swale as <br />designed is acceptable for both detention and water quality <br />treatment. <br />