C. HYDRAULIC STANDARDS AND PROCEDURES

1. General Hydraulic Criteria

  • Hydraulic calculations will be in accordance with “Los Angeles County Flood Control District Design Manual, Hydraulic”, latest edition.
  • Closed conduits may be designed as flowing full and may be allowed to flow under pressure if the hydraulic grade line is sufficiently below the street surface to intercept catch basin flows with a minimum of 0.5 ft. freeboard in the catch basin below the gutter invert. (For catch basins outletting to detention or retention basins, this requirement may be waived by the City Engineer.) See Figure V-8.
  • In any street or highway, the depth of water at curb times the velocity shall not exceed six. When this condition cannot be met, catch basins will be required to intercept the flow.
  • Where debris may be expected, the design flows will be increased by an appropriate bulking factor.
  • All closed conduit designed to flow under pressure, including connector conduit from catch basins to main line storm drains, shall be constructed with watertight gasket-type joints per section 306 of the Standard Specifications for Public Works Construction published by the American Public Works Association.

2. Design Requirements for Manholes

  • Spacing - Manholes shall be located at beginning or ending of curves, pipe size changes, angle points, junctions and as required for maintenance.
  • Conduit diameter 30 inches or smaller, manholes shall be spaced at intervals of approximately 300 feet. Where the proposed pipe is less than 30 inches in diameter and the horizontal alignment has numerous bends or angle points, the manhole spacing shall be reduced to approximately 200 feet.
  • Pipe diameter larger than 30" but smaller than 45", manholes shall be spaced at intervals of approximately 400 feet.

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