Published: January 20, 2023

This Drainage Design Manual has been prepared as a guide for the hydraulic design of highway drainage facilities. Drainage is one of the essential components of roadway design.

Drainage criteria and design outlined in this manual reflects the maximum standard achievable that is based on new project development for traditional design, bid, and build projects. Existing conditions represent the minimum standard, which should always be evaluated against the cost of achieving the maximum standard and the purpose and need of the project. The goal is to make an improvement commensurate with the purpose and need of the project at minimized project costs without negative impacts to safety. Coordinate any proposed deviations from the maximum standard with the Department prior to incorporation into the design.

Drainage facilities for most roadway projects account for approximately 25% of the total construction cost of the project. This cost justifies a careful and scientific hydraulic analysis.

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