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k 4 <br />V11f <br />TABLE 1 <br />TOTAL PRECIPITATION <br />FREQUENCY -DURATION TOTAL RAINFALL <br />(YR-HR) (INCHES) <br />10YR-24HR <br />2.23 <br />25YR-24HR <br />2.67 <br />(Reference rainfall hyetographs for the City of Everett, <br />Appendix I). <br />From the respective rainfall hyetographs, 72 time <br />segments consisting of 20 minute intervals were used for <br />modeling single storm events of 24 hours duration. <br />3.0 EVALUATION OF SITE HYDROLDOY UNDER PRE -DEVELOPED <br />CONDITIONS <br />In order to simplify analysis of the existing conditions, <br />the project site was divided into two major basin areas) <br />the northwest basin and southwest basin. Areas within <br />each basin were determined based on land use/cover <br />conditions and categorized as either pervious or <br />impervious areas. The effective widths of each basin area <br />was determined using procedures outlined on Page 102 of <br />the SWMM manual. <br />5 <br />9 <br />