SBUH Calculation Worksheet for City of Eugene Storm Events <br />Project Name: Braewood Date: 8/28/25 <br />Designer: ALB Basin: Swale 3 (Basin S3, L5) <br />User-Supplied Data <br />Pervious Area Impervious Area <br />Pervious Area, SF 60,649 60,649 Pervious Area, Acres 1.39 1.39 <br />Pervious Area Curve Number, CNperv 76 98 <br />Time of Concentration, Tc, minutes5 Note: minimum Tc is five minutes <br />City of Eugene 24-Hour Rainfall Depths (NRCS Type 1A distribution) <br />Recurrence Interval WQ 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr <br />Inches 1.56 3.12 3.6 4.46 5.18 6 6.48 <br />Calculated Data <br />Total Project Area, Acres 2.78 Total Project Area, Square Feet 121,298 <br />Recurrence Interval WQ 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr <br />Peak Flow Rate, Qpeak, cfs 0.54 1.44 1.76 2.35 2.86 3.45 3.81 <br />Total Runoff Volume, V, cubic feet 7,835 20,138 24,282 31,952 38,550 46,204 50,739 <br />Time to Peak Runoff, hours 7.83 7.83 7.83 7.83 7.83 7.83 7.83 <br />Runoff Hydrograph <br />Impervious Area, SF <br />Impervious Area, Acres <br />Impervious Area Curve Number, CNimp0.000.501.001.502.002.503.003.504.000 500 1000 1500 2000 2500Runoff, cfsTime, minutesWQ2-Year5-Year10-Year25-Year50-Year100-Year 800 Willamette Street, Suite 400 Eugene, OR 97401 541.684.4902 kpff.com