Culvert and storm drain systems constitute critical nodes in U.S. transportation networks, providing pathways for water to move through highway embankments and providing structural support to our roadways. Most states have an inventory of three to five times more culverts than bridges. In the last 20 years, the transportation industry has advanced funding to start to address the deferred maintenance on these structures by developing rehabilitation methods, creating rehabilitation products, and writing a new in-service inspection guide. Unfortunately, these methods are not assembled in a readily usable manner for highway agencies.

The recent AASHTO Culvert and Storm Drain System Inspection Guide (CSDSIG) provides a roadmap for the inventory and inspection of culverts and storm drains. The next logical step is to determine a course of action for assets identified as deficient.  Guidance on when to replace versus rehabilitate and the choice of a rehabilitation method are current gaps in knowledge that are not captured in national guidance. In addition, guidance for design of the rehabilitation methods is not standardized. The development of an AASHTO Rehabilitation Design Guide will overcome this problem.

The objective of this research is to develop a comprehensive guide for designers to use when deciding between the replacement or rehabilitation of culverts and storm drains. The guidance will assist designers in the selection of the most appropriate rehabilitation method(s) and the applicable loading conditions and design method to use when applying the chosen method. 

Proposed Tasks:

·       Review and summarize existing literature on culvert rehabilitation methods, discussing the methods available, their limitations, and their appropriate use.

·       Locate and summarize case studies that would demonstrate the various rehabilitation methods.

·       Determine critical factors to consider when determining whether to replace or rehabilitate a structure, and how to choose a proper rehabilitation method and augment the AASHTO CSDSIG with necessary condition information to be collected as input into the decision on rehabilitation or replacement and as input to complete the rehabilitation designs.

·       Provide guidance on the loading conditions and existing design methods to use for the various rehabilitation methods, including the identification of existing knowledge gaps for future research.

·       Provide guidance for the establishment of design properties so that rehabilitation methods can be calibrated to provide a similar factor of safety for given design loads.

·       Develop a recommended AASHTO Culvert and Storm Drain System Rehabilitation Design Guide for departments of transportation and other agencies implementing the findings of the research.