Synthesis of Information Related to Highway Practices. Topic 53-05. Practices for Stormwater Bioretention

Bioretention is one of the most common stormwater control measures used by municipalities, and state departments of transportation (DOTs) are increasingly being asked to use bioretention to meet federal National Pollutant Discharge Elimination System stormwater permit requirements. Some state DOTs, like Washington State DOT, have integrated aspects of bioretention into their roadway embankment, such as vegetated filter strips, compost amended vegetated filter strips, and media filter drains that treat stormwater as part of the roadway embankment. The objective of this synthesis is to document current state DOT practices for bioretention design, construction, and maintenance, as follows: (1) Siting constraints, including nearby contaminated soil, groundwater, or wetlands, high sediment loads, and steep terrain or erodible soils; (2) Requirements for physical and chemical characteristics of bioretention soil mix (e.g., content, gradation, nutrients, micronutrients, or source material); (3) Allowances for bioretention soil mix variations or substitutions (e.g., biochar amendments); (4) Local sourcing requirements for materials; (5) Quality control requirements (e.g., project-specific material acceptance criteria prior to placement); (6) Underdrain usage guidance (e.g., when to use an underdrain), underdrain matrix material (e.g., specifications for crushed rock or permeable base), and underdrain pipe material, elevation, and slope; (7) Written state DOT guidance on the use of impermeable liners; (8) Compaction requirements (inside and outside clear recovery zones); (9) Outlet control (flow restriction or elevation); (10) Plant type, including allowance for trees; (11) Use of temporary or permanent irrigation; (12) Operations and Maintenance inspection and maintenance protocols, feasibility evaluation criteria, and considerations affecting design; (13) Cost-benefit guidance for using enhancements for water quality (e.g., more expensive filter media); and (14) Bioretention-related terms and definitions (e.g., raingardens vs. bioretention vs. bioswales and planting soil vs. bioretention mix vs. filter media). Information will be gathered through a literature review, a survey of state DOTs, and follow-up interviews with selected agencies for the development of case examples. Information gaps and suggestions for research to address those gaps will be identified.


  • English


  • Status: Active
  • Funding: $45000
  • Contract Numbers:

    Project 20-05, Topic 53-05

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Gause, Jo

  • Start Date: 20210524
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01771595
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-05, Topic 53-05
  • Files: TRB, RIP
  • Created Date: May 17 2021 3:14PM