Laserfiche WebLink
Example: <br />A 3-acre site in the Narbeck Creek Drainage basin is to be developed <br />from its present forested condition to a small shopping center. <br />For purposes of this example, assume the site is not located in a <br />critical drainage area. Paved parking areas and rooftops will cover <br />95% of this site with the balance to be landscaped. There is no <br />off -site drainage and the most distant point from the outlet is 630 <br />feet. The approximate slope of the site is 4%. <br />SOLUTION: <br />1. from table 1, an appropriate c is .05 <br />exist <br />2. from table 1, velocity = .5 ft/sec therefore, <br />Tc = 630 + 10 = 31 min. <br />.5 F60) <br />t 3. from figure 1,intensity, "i", = I.02 in/hr <br />t <br />4. Since there is no of: -site drainage, the tributary area = area of the site = 3.0 <br />5. Qallow = (•05) 0.02) (3) _ .153 <br />6. This site is not in the combined sewer area, therefore, the design storm is <br />the 25-year storm. <br />7. (a) Cdev = (0.95) (0.9) + (0.2) (.05) = 0.865 <br />(b) Qo = allow = 153 = .059 <br />(AACdev (3�865) <br />(c) T = -25 2706 = -25+ 2706 <br />Qo 059 <br />T = 189 <br />(d) Vs = 4329T -40QoT <br />T+25 <br />Vs = 4329089)-40(o.59) (189) <br />189 + 25 <br />Vs = 3377 cf/acre imperviousness <br />(e) Vt z (VsHA)(Cdev) <br />Vt = (3377) (3) (0.865) <br />Vt = 9763 cf <br />