California Department of Transportation

Project Development Workflow Tasks (PDWT)

Part 3 - Identify Project Need and Project Initiation Document

II. Project Initiation Document

B. Develop Initial Alternatives (150.10) - Develop Concept Alternatives (WBS 150.10.15)

P55. Request Preliminary Hydraulic Review

The Hydraulics Department performs detailed scoping during the PID and PR phases to lay the groundwork for drainage improvements. The cost of a seemingly simple AC overlay project may double due to hydraulics recommendations. Hydraulic recommendations can involve areas that are beyond the proposed roadway construction, greatly increase project construction costs, and add to the areas that must be assessed during the preliminary environmental assessment. Discharge of roadway runoff to sensitive streams and waterways also fall under stringent controls and have significant project impacts. Failure to obtain Hydraulic and Hydrology recommendations early may lead to scope changes, cost increases and project delays later on. The project engineer must provide as much information available about the existing facility and the proposed project when requesting the hydraulics investigation. The following items should be provided if available:

  • Proposed roadway alignment (strip map)
  • Typical sections
  • Profile
  • Superelevations
  • Description of the proposed alternatives
  • As-Built records of the existing facility
  • Right of way maps
  • Location and capacities of existing pump plants

The Hydrologic review typically includes a review of the watershed areas and potential flood zones adjacent to and within the highway right of way. The Hydraulics review typically includes a review of the existing drainage control features, including the condition of existing culverts, inlet and outlet conditions, headwalls, storage capacities of retention and detention areas, temporary and permanent storm water control, and pumping plants. Due to the extensive age of many highway facilities, replacing aged and deteriorated culverts with new and larger culverts is one of the most common recommendations. The replacement of cross-culverts will likely involve other associated project costs and constructibility issues including the need for additional traffic control, excavation, temporary K-railing, raising roadway profiles to cover larger culverts, etc. The project engineer should be aware that the Hydraulic/Hydrologic recommendations do not include a preliminary cost estimate; it is up to the project engineer to determine what associated costs and issues will result.

Hydraulic and Hydrology reviews involving bridge structures are covered by the Advance Planning Study (APS) which is performed by the DES Structure Design (refer to the Request Structures Advance Planning Study task). The project engineer must coordinate roadway Hydraulic/Hydrology recommendations with Structures APS recommendations.

Time Constraints:

Lead-time requirement for the first preliminary drainage analysis is one month for simple arealignment project with minimal hydraulics issues, two to three months for major realignment or new alignment projects.



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This page last updated October 20, 2010