Geotechnical Considerations for Design-Build Highway Contracts

Since 2000, the Minnesota Department of Transportation (Mn/DOT) has designed and constructed selected transportation projects using design-build contracting. Design-build contracting combines, rather than separates, the design and construction phases of a project, and this is what differentiates it from the traditional design-bid-build method of contracting. With the advent of design-build, a debate began within Mn/DOT regarding when the geotechnical exploration should be performed in the process, who should perform the geotechnical exploration, and who would assume the responsibilities and risks of the geotechnical exploration. One side argues that a minimal geotechnical investigation should be performed to prepare the contract documents, leaving the responsibility and risk for the geotechnical exploration to the design-build engineer. The other side advocates performing, as completely as possible, the geotechnical exploration and analysis as part of the preparation of the contract documents, leaving the responsibility and risk to Mn/DOT or to Mn/DOT's consultant for the contract documents. This paper discusses the advantages and disadvantages of each side of the debate and the impacts on current design-build projects. The discussion includes the author's experience as the lead geotechnical engineer on the Trunk Highway 100 Segment 5 design-build team and as the lead geotechnical engineer for preparation of the contract documents for the Interstate 494 design-build contract.