Construction

Culverts are constructed from a variety of materials and are available in many different shapes and configurations. When selecting a culvert, the following should be considered:
  • roadway profiles
  • channel characteristics
  • flood damage evaluations
  • construction and maintenance costs
  • estimates of service life.
Numerous cross-sectional shapes are available. The most commonly used shapes are circular, pipe-arch and elliptical, box (rectangular), modified box, and arch. Shape selection should be based on the cost of construction, limitation on upstream water surface elevation, roadway embankment height, and hydraulic performance. Commonly used culvert materials include concrete (reinforced and non-reinforced), steel (smooth and corrugated), aluminum (smooth and corrugated), and plastic (smooth and corrugated).
The selection of material for a culvert depends on several factors that can vary considerably according to location. The following groups of variables should be considered:
  • structure strength, considering fill height, loading condition, and foundation condition
  • hydraulic efficiency, considering Manning’s roughness, cross section area, and shape
  • installation, local construction practices, availability of pipe embedment material, and joint tightness requirements
  • durability, considering water and soil environment (pH and resistivity), corrosion (metallic coating selection), and abrasion
  • cost, considering availability of materials.
The most economical culvert is the one that has the lowest total annual cost over the design life of the project. Culvert material selection should not be based solely on the initial cost. Replacement costs and traffic delay are usually the primary factors in selecting a material that has a long service life. If two or more culvert materials are equally acceptable for use at a site, including hydraulic performance and annual costs for a given life expectancy, bidding the materials as alternates should be considered, allowing the contractor to make the most economical material selection.