Geotechnical baseline reports – ground models you can just make up?

Geotechnical Baseline Reports (GBRs) are a purely commercial form of ground model, used to allocate ownership of unforeseen ground risk in a construction contract. They are used at tender to provide a common basis for pricing risk and they are used during construction to provide an efficient means of managing claims involving potentially unforeseen ground conditions. One of the ways in which GBRs are different from conventional ground models is that they do not necessarily have to present objective data-based truths about the ground. This possibility arises because clients have varying appetites and abilities to take on construction risk. GBRs can be difficult to write because they are focused on encounters with the ground during construction and these experiences are often indirect and significantly different to encounters in ground investigations. This construction knowledge and the commercial nature of GBRs mean a multi-disciplinary approach to writing GBRs is preferred. The profession best able to characterize the risk inherent in the ground is the engineering geologist through knowledge of ground models. GBR ground models can be considered to be a distinct commercial variant and development of the engineering ground models described in the IAEG’s CS25 report on the subject. © 2020 The Author(s). Published by The Geological Society of London.