1. Conduit diameter 45" or larger, manholes shall be spaced at intervals of approximately 500 feet.
  2. The spacing requirements shown above apply regardless of design velocities. Deviations from the above criteria shall be subject to City of Palmdale approval.
  3. Location - manholes shall not be located in street intersections where possible, especially when one or more streets are heavily traveled.
  4. In situations where the proposed pipe is to be aligned both in easement and in street right-of-way, manholes shall be located in street right-of-way, wherever possible.
  5. Manholes shall be located as close to changes in grade as feasible when the following conditions exist:
  6. The upstream pipe has a steeper slope than the downstream conduit and the change in grade is greater than 10 percent of the upstream slope. Sediment tends to deposit at the point where the change in grade occurs.
  7. Transitioning to a smaller downstream pipe due to an abruptly steeper slope downstream. Smaller downstream pipe shall not be allowed except extreme downstream conditions require the use of a smaller downstream pipe. The use of smaller downstream pipe will be subject to written approval of the City Engineer. In cases where storm drains pass through and are discontinuous through detention basins this rule does not apply.
  8. Design - When the design flow in a pipe flowing full has a velocity of 20 fps or greater, or is supercritical in a partially full pipe, the total horizontal angle of divergence or convergence between the walls of the manhole and its center line shall not exceed 5circ 45'.
  9. Pressure Manholes - Pressure manholes shall not be allowed. Exceptions may be made on a case-by-case basis with written approval of the City Engineer.

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