7.7.7 Storm Drains
The primary aim of a storm drain design is to limit the amount of water flowing along the gutters or ponding at low points to quantities which will not interfere with the passage of traffic or incur damage to the highway and local property. This is accomplished by placing appropriately sized inlets at the proper spacing.
Since storm drains receive water through inlets and carry the water through long underground conduits, it is desirable to maintain a minimum self-cleaning velocity in storm drains to prevent deposition and loss of capacity. Repair or replacement of storm drains can be expensive.
Considerations in the hydraulic design of storm drains include:
- Storm drains which drain sag points where runoff can only be removed through the storm drainage system must be designed for a minimum 50-year frequency storm;
- Maintain ongoing communication with the roadway design engineer regarding roadway design changes affecting drainage. Make recommendations concerning geometric modifications that would result in more desirable drainage improvements; and
- Perform clash detection to eliminate conflicts with existing or proposed utilities.