A concrete culvert is required to convey a design flow of 654 cfs over a length of 330 ft, and a slope of .015ft/ft. Because there is a large lake downstream, the tailwater elevation is constant at 536.3 ft MSL, which will submerge the culvert outlet. The headwater elevation cannot exceed 544.4 ft MSL, without overtopping the roadway embankment. Find the required diameter for (a) a single barrel culvert and (b) twin barrels assuming a square edged entrance.