DESIGN CLOSED CULVERTS
Critical Tasks: 01-1990-20-1002
This lesson covers the aspects of designing a culvert (closed channel) for a given situation. In summary, this
means selecting the right size, shape, and construction material, plus planning the placement. Design is based on
environmental considerations such as slope, flow, and length of culvert needed, in addition to economic
TERMINAL LEARNING OBJECTIVE:
Identify characteristics of closed culverts, determine factors for placement of closed
culverts, and design closed culverts.
You are given this subcourse, a No 2 pencil, paper, and an ACCP examination response
Demonstrate competency of the task skills and knowledge by responding correctly to 70
percent of the examination questions.
The material contained in this lesson was derived from the following publications: None
The purpose of this instructional material is to discuss, explain, and illustrate the factors that enter into the design,
placement, and construction of culverts.
Before proceeding, it is necessary to define the terms found in general use in culvert practice. Look at figure 5-1,
page 5-2 for the terms used.
Culvert -- A culvert is an enclosed waterway placed through an embankment or fill. Culverts are used in
many ways; to continue natural streams through an intercepting structure, to provide cross drainage in a
fill section, to provide ditch relief and to continue side ditches at road intersections. Their efficiency in
conveying water, strength, and ease of construction often make them more desirable than small bridges.
Fill or embarkment -- The soil mass through which the culvert carries the flow of water.
Headwall -- Retaining wall always employed at the upstream end of culvert; can be used downstream. Its
purpose is to support and protect the soil mass at the end of the culvert.