Civil Engineering PE

Answer: B - The scouring velocity of gravity sanitary sewers is considered to be 2 ft/sec. Typically, state regulatory agencies require that sewers be designed and constructed so that the mean velocity, when flowing full, is not less than 2.0 feet per second, based on a Manning’s formula using an “n” value of 0.013. However, slopes that provide a velocity greater than the minimum 2 ft/sec are recommended so that a scouring velocity can be achieved within the pipe at low flow periods and/or to address the increasing use of low flow plumbing fixtures that contribute less flow to a collection system that may have been considered in the design per capita daily flow assumptions.