Changes

[[File:underdrain-subgrade.jpg|300px|thumb|right|Underdrain installed to subgrade.]]

[[File:underdrain-subgrade.jpg|300px|thumb|right|Underdrain installed to subgrade.]]

[[File:underdrain-with-risers.jpg|300px|thumb|right|Underdrain installed with maintenance risers. Note the 'T' joints, which are no longer recommended.]]

[[File:underdrain-with-risers.jpg|300px|thumb|right|Underdrain installed with maintenance risers. Note the 'T' joints, which are no longer recommended.]]

====Underdrains====

===Backfill Granular, Utilities and Pipes: Underdrains===

[[Underdrains]] are perforated pipes that  collect subsurface water and convey water out of an LID facility once it reaches capacity. Their design is determined by the drainage requirements of the feature.

[[Underdrains]] are perforated pipes that  collect subsurface water and convey water out of an LID facility once it reaches capacity. Their design is determined by the drainage requirements of the feature.