Overflow: Installation

From LID SWM Planning and Design Guide
Revision as of 14:24, 21 July 2022 by JamesCowan (talk | contribs)
Jump to navigation Jump to search

Overflows[edit]

Overflows are features of inline facilities and convey larger storm events out of the LID feature.

Construction Steps:

  1. Connect the overflow drain to the underdrain.
  2. Install overflow pit to grade at the location specified in the contract documents.
  3. Fit a metal, domed grate to the overflow.

Key Inspection Points:

  • Overflow drain matches design specifications.
  • Overflow pit is positioned at the maximum water surface elevation of the practice, as per the contract documents.
  • Sufficient freeboard is provided between the overflow and inlet such that the inlet is not inundated by design storm flows.
  • Overflow grate matches design specifications.
  • Overflow grates located in high-traffic areas are screwed on or equipped with locks.

Mistakes to Avoid:

  • Backflows – ensure that backflows are avoided by confirming that inlet and overflow elevations match design specifications with surveys.
  • Incorrect sequencing – install overflow drain prior to backfilling with granular material and engineered soil.
  • Incorrect grate material – avoid using plastic overflow grates due to breakages and UV degradation.