The hydraulic length (longest flow path) for a watershed is 2,800 ft. Along this path, runoff initially travels over the land surface (dropping 4 ft in elevation over 200 ft in length through short grass) and then moves into shallow concentrated flow for a distance of 600 feet with an average velocity of 2 ft/sec. The remainder of the travel path is through a 2-ft diameter (concrete) pipe flowing half-full on a 1-percent slope. Determine the time of concentration in minutes. The 2-yr, 24-hr rainfall depth is 3.4 in.