• Deep Manholes - A manhole shaft safety ledge shall be provided in all instances when the manhole shaft is 20 feet or greater in depth. Installation shall be in accordance with Los Angles County Flood Control District Standard -Drawing No. 2-D430.
  • Inlets into Main Line Drains - Lateral pipe entering a main line pipe storm drain generally shall be connected radially. Lateral pipe entering a main line box structure shall conform to the following:
  • Invert of lateral pipe 24 inches or less in diameter shall be no more than five feet above the invert.
  • Invert of lateral pipe 27 inches or larger in diameter shall be no more than 18 inches above the invert, with the exception that catch basin connector pipe less than 50 feet in length may be no more than five feet above the invert.
  • Minimum Pipe Size - The minimum diameter of mainline and catch basin connector pipe shall be 18 inches.
  • In cases where the pipe may carry significant amounts of debris, the minimum diameter of main line pipe shall be 36 inches.
  • Minimum Slope - The minimum slope for main line pipe shall be .001 (.10 percent), unless otherwise approved by the City Engineer. Pipe design shall allow for sufficient velocity to prevent silting.
  • For debris carrying storm drains, the minimum pipe slope shall be 0.03 (3 percent).
  • If the surface grade is less than 3 percent, a debris basin will be required upstream of the area which does not meet this criteria.
  • Inlet Structures - An inlet structure shall be provided for storm drains originating, in natural channels. The structure shall generally consist of a headwall, wingwalls to protect the adjacent banks from erosion, and a paved inlet apron with a minimum 4 feet deep cutoff wall. The apron slope should be limited to a maximum of 2:1.

V-7