Early this year, NCHRP released a synthesis report on geotechnical practices related to design-build projects. I have had writing a blog post on this on my “to do” list for a few months and finally got down the list!
NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects is a report on the current practices of allocating and managing geotechnical risk through the use (or lack of!) geotechnical information in transportation project bid documents. Even though design-build as a delivery process for projects has been around for a while now, the allocation of risk due to subsurface conditions is an issue still treated with a variety of approaches.
Those of us who have been in this industry for a while know that a thorough geotechnical investigation reduces both cost risk and construction/schedule risk. Design-build is an effective method for accelerating project construction and delivery; however, the acceleration of the schedule puts more pressure on the geotechnical design since “geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award.”
Because geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award, the design-builder’s geotechnical designers are under pressure to complete their work and enable foundation and other subsurface construction to commence. Successfully managing the geotechnical risk in a DB project is imperative to achieving the requisite level of quality in the finished product. The purpose of this synthesis is to benchmark the state of the practice regarding the use of geotechnical information in DB solicitation documents and contracts. The high level federal encouragement through EDC for state DOTs to accelerate project delivery by using DB elevates the need to manage geotechnical risk while expediting geotechnical design to a critical project success factor, and makes the results of this synthesis both timely and valuable.
As is the case with NCHRP synthesis reports, the authors conducted a literature review, conducted a survey of state DOTs and other agencies, and developed some conclusions that include effective practices for managing geotechnical risk.
The synthesis was based on a comprehensive literature review; a survey of U.S. DOTs, which received responses from 42 states (response rate = 84%); a content analysis of DB solicitation documents from 26 states; a content analysis of DB policy documents/guidelines from 12 state DOTs and 5 federal agencies; and interviews of 11 DB contractors whose markets encompass more than 30 states. The synthesis also furnishes three legal case studies (Colorado, Illinois, and Virginia) on cogent geotechnical issues and four geotechnical engineering case studies (Hawaii, Minnesota, Missouri, and Montana) that illustrate the methods transportation agencies use to deal with geotechnical issues on DB projects. Conclusions were drawn from the intersection of independent sources of information from the survey, case studies, and literature.
Some of the effective practices highlighted include the use of confidential Alternative Technical Concepts (ATC) during pre-bid, explicit differing site conditions (DSC) clauses that clearly quantify the design-build team’s risk and the threshold above which the DOT assumes the risk, the use of qualified personnel, and timely review schedules for geotechnical design items early in the project.
Our (DBA) experience in design-build has seen the range from effective practices to poor practices. This report provides a great summary of many of the effective practices we have found to be beneficial and that help reduce conflicts and delays. We can’t completely eliminate geotechnical risk, but it can be effectively and equitably managed.
Click on the link below to get a copy from NCHRP.