The material in this report will be of immediate interest to agencies and consultants to identify and evaluate opportunities to measurably reduce the levels of geotechnical uncertainty before contract award, as well as equitably distribute the remaining risk between the parties during contract execution so that there is a positive impact on project cost and schedule.
Mitigating the risk of differing geotechnical site conditions is never simple, but in a design-build (DB) contract awarded before a complete subsurface investigation is completed, it becomes even more difficult. While DB project delivery is a proven tool for accelerating badly needed renewal projects, it does so by awarding the contract before design is complete. Typical DB highway projects often provide only a small fraction of the necessary geotechnical investigation required by the state DOT geotechnical manual of instruction at the time of procurement. These DB contracts require the DB team to conduct the full subsurface site investigation and geotechnical design report in final design. As a result, construction costs could increase due to unforeseen site conditions. Since current DB case law has shown that the agency cannot effectively shed risk due to differing site conditions, efforts were needed to mitigate the risk of both cost and time overruns if actual conditions are found to differ significantly from those portrayed in the project’s DB request for proposal (RFP).
Under NCHRP Project 24-44, Iowa State University was asked to develop guidelines for the implementation of geotechnical risk management measures for DB project delivery related to geotechnical investigation, design, and construction.