Final Scope

State departments of transportation (DOTs) have traditionally designed structures to convey water under roads based on cost, hydraulic efficiency, and risk criteria. However, this design approach can result in barriers to aquatic organism passage (AOP) as an unintended and undesired consequence. Thus, state DOTs have come under increasing regulatory direction to ensure AOP through structures.

State DOTs on the West Coast and in the Northeast have been dealing with AOP for some time now, initially motivated by state and federal regulatory requirements, and now sometimes by legal challenge. Design practice in these state DOTs has settled on a suite of generally accepted approaches and practices calling for a higher level of geomorphic and hydraulic design than was formerly the case. Modern AOP design typically entails an interdisciplinary approach relying on various combinations of hydraulic engineers, hydrologists, fluvial geomorphologists, and biologists.

As a result of AOP design, structures have gotten larger, streambed placement and construction is now a routine practice, and 3-sided and open-bottom structures are strongly encouraged by regulators and resource agencies. Project scopes and costs have increased as compared to traditional hydraulic capacity designs. Some state DOTs have elected to address AOP programmatically while others have proceeded on a project-by-project basis. Along with these challenges has come that of institutional capacity. State DOT staffs may not have the numbers, skills, or experience, nor do many of the consultants who have traditionally functioned as extensions of DOT staffs.

The objective of this synthesis is to document state DOT practices and activities in designing, constructing, and monitoring structures that deliver aquatic organism passage.

Information to be gathered includes (but is not limited to):
• Extent of state DOT adoption of AOP practices;
• Aquatic organisms typically considered in AOP design;
• Existence of written DOT policy and guidance for AOP design;
• Design methodologies (e.g., geomorphic assessment, stream simulation process, hydraulic design);
• Programmatic or project-by-project approach;
• Accommodation of culvert rehabilitation and retrofit;
• Extent of culvert upsizing and cost impacts;
• Basis for prioritization of structures for replacement (e.g., condition, habitat improvement);
• Construction practices (e.g., contractor training, regulatory compliance, channel divergence, dewatering methods, inspections, streambed construction);
• Streambed materials specification and procurement (e.g., standard, general, or project specific specifications);
• Crossing structure specification and procurement (e.g., standard, general, or project specific specifications);
• Project delivery methods (e.g., design-build, design-bid-build);
• Internal AOP program organization, staffing, and training;
• Performance monitoring practices and results;
• AOP asset management practices;
• Secondary benefits realized by DOTs from AOP practices (e.g., increased resiliency, wildlife crossing, wetland and floodplain connectivity, reduced maintenance activities).

Information will be gathered through a literature review, a survey of state DOTs, and follow-up interviews with selected DOTs for the development of case examples. Information gaps and
suggestions for research to address those gaps will be identified.

TRB Staff
Jo Allen Gause
Phone: 202-334-3826
Email: jagause@nas.edu

Meeting Dates
First Panel Meeting: September 12, 2023, Washington, DC
Teleconference with Consultant: October 18, 2024 from 1:00 – 2:00pm Eastern
Second Panel Meeting: June 4, 2024, Washington, DC

Panel Members
Gillian O'Doherty, Federal Highway Administration (FHWA)
Dr. Arthur Parola, University of Louisville
Mark Lickus, Maine Department of Transportation
Steve Neary, Wisconsin Department of Transportation
Julie Heilman, Washington State Department of Transportation
Deborah Wiseman, Tennessee Department of Transportation
Tracey Janus, Texas Department of Transportation
Brian Roberts, Transportation Research Board