Box Culvert Design

Document Type

Student Presentation

Presentation Date

April 2016

Faculty Sponsor

Mandar Khanal


The Robertson Slough Bridge, built in 1927, is being considered for replacement by the Idaho Department of Transportation. Civil Engineering Senior Project Team, X^(3 )Engineering proposes a box culvert design that acts as a bridge to meet the structural, geotechnical, hydraulics, and transportation requirements set forth by American Association of State Highway and Transportation Officials (AASHTO) standards. The bridge is located on US-95 outside Weiser, ID. The area lies within the floodplain of the Weiser River so the box culvert was designed to convey the flow for a hundred year flow event underneath the roadway. The new design, a two box culvert with a mat foundation and retaining wall, will extend and expand the roadway to meet modern traffic flow. The dead and live load of the roadway has been obtained from ASHTO standards. After reviewing all detour options, realigning the road both horizontally and vertically is the best choice to allow continuous traffic flow in US-95 during construction. Subsurface investigation shows the surrounding area of the existing bridge has poorly drained load overlaying gravelly sand with ground surface of linear slope from zero to three percent. Based on these conditions, the dead load of the boxes and the loads on the wing walls along with horizontal and vertical alignments have been designed to meet with these conditions. An environmental impact study will be investigated before and after constructing the box culvert, such as removing and planting vegetation that involves permits and codes of Washington County.

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