Membrane-level Drainage on Highway Bridge Decks

Drive under highway bridges in some parts of the U.S. and you may notice a series of small-diameter PVC pipes that extend down a few feet from the edge of the bridge and end in mid-air. The often-irregular spacing and skew angles of these pipes may appear haphazard, but their appearance belies the fact that this system of pipes is a carefully designed feature that serves a critical purpose. These pipes are drains, but they do not typically drain the surface of the pavement. Instead, they provide a drainage outlet for the waterproofing membrane on the structural bridge deck to relieve water that infiltrates the pavement layer due to its inherent porosity or at cracks and joints.

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