The Smiley Road Culvert project is located on the Terry and Smiley Tributary in the City of Bridgeton, MO. The project consists of improving the approaches to the new 4ft x 8ft double box culvert under Smiley Road.  Identified in the City’s stormwater masterplan as PI-29, the project was originally intended to stabilize the adjacent stream banks upstream and downstream of the culvert.  The project was expanded to include energy dissipation at the outfall and inlet improvements. 


Intuition & Logic was retained to design the bank stabilization, inlet and outlet improvements.  The bank stabilization consisted of rock armor with livestakes extending 60 feet upstream and downstream of the culvert.  The inlet improvements consisted of a 60 foot long, 2 foot tall, sloping weir wall designed to mimic the stream forming flow depth in the approach channel in order to maintain sediment continuity through the culvert crossing and keep the second barrel offline during low flow events.  During flood flow, the higher flood depths allows water to cross the weir wall and make use of the second barrel’s conveyance capacity. 


Downstream of the culvert, a 50 foot long rock armored stilling basin was constructed for energy dissipation.  An 8 foot long 2 foot tall flow separation wall was constructed at the culvert outlet to prevent sediment deposition from occurring downstream of the offline barrel due to the rapid expansion and energy loss that occurs during low flow conditions.  The length of the flow separation wall was determined by analyzing the extents of the ineffective flow area during stream forming flow conditions.