Geotechnical baseline reports: a guide to good practice (C807)

Introduction

The UK Construction Research body CIRIA released back in January 2023 a good practice guide for geotechnical baseline reports, which are used to manage commercial risk of ground conditions on subsurface projects.

Titled Geotechnical baseline reports: a guide to good practice (C807).

Available for purchase for ￡90 from CIRIA as a PDF here

A geotechnical baseline report (GBR) is basically a contract document that describes a set of defined ground conditions tenderers are assumed to have allowed for when bidding for work. After contract award the GBR is used to determine the validity of ground based claims that might arise during construction.

I am a big supporter of GBR’s and have previously written about GBR’s here, here and here so I thought it opportune to update and deep dive into the Report.

The Guide to Good Practice was authored by Mott MacDonald technical director Antony Drake, Geotechnical Consulting Group senior partner John Davis, RJ Essex principal and tunnel consultant Randall Essex (Mott MacDonald retiree) and Mott MacDonald geotechnics practice lead Imran Farooq.

The authors were assisted by Mott MacDonald technical principal and New Engineering Contract (NEC) and procurement specialist Richard Patterson as a key contributor and the project’s steering group which comprised client, contractor and consultant representatives. The steering group was chaired by Jacobs engineering geology head of discipline Thomas Berry.

The authors were later interviewed by Ground Engineering magazine, a detailed interview article is available here and is a must read if you are considering on embarking on using a GBR, some handy tips.

The organisations that helped fund the production of the guide were Bam Nuttall, the British Geotechnical Association, the British Tunnelling Society, HS2 Ltd, Fugro, GCG, Jacobs, Mott MacDonald and National Highways. So a minor remark is it is UK centric as it only relates to the NEC contract and not the FIDIC Emerald Book which is used internationally on tunnelling projects. A missed opportunity perhaps picked up in an update?

?Mott MacDonald technical director Antony Drake, who is also one of the GBR guide’s authors, is quoted as saying : “The intent is to have a contractually clear allocation of risk in relation to unexpected conditions or expected conditions on a project that we’re trying to set some boundaries for. “And the ultimate aim is clarity about where the responsibility of the contractor ends and where the responsibility for the client would kick in.”

This is the very fundamental basis of a GBR. No surprises and if there are surprises then the allocation is clear.

The Guide in Figure A1 shows a 4 bucket set-up. So 2 buckets for the Client and the same for the Contractor either within or outside the GBR.

NEC has come up with what one could consider a Practice Note when using a GBR with a NEC Contract. It is available here

As one can see with the Practice Note some amendment to the Core Clauses by way of Z clauses are necessary to deal with GBR’s. Perhaps in future the NEC4 could include Optional clauses?

Also the notion of the ‘experienced contractor’ risk as "Something [outside] that an experienced contractor would have judged at the contract date to have such a small chance of occurring that it would have been unreasonable to have allowed for them is retained as the 4th bucket even though a GBR is being used.

This arrangement is somewhat unsettling. Only Something other than having a small chance of occurring is Contractor risk. Everything else is effectively Client risk. The size of the boxes perhaps give a clue.

If one looks at Figure A1 then one could say that for items not covered by the GBR the Client has a disproportionate risk allocation. Was this the intention of the drafters? Surely it would be better for a Client to get input from tenderers as to their GBR and whether it covers all likely unknowns and reduce this risk?.

I note that the Authors have extensive experience using GBR’s in action with 30-odd GBRs for Crossrail, I wonder if items outside the GBR descriptions were encountered and how they dealt with them. ?

John Davis rightly noted that you still need to be thinking about the GBR from the start of a project.

“You can also have an early stage GBR used in a staged tendering process which may then be subsequently negotiated and revised either to account for what the contractor would like to see in that document, or potentially also to account for new information or design or alignment changes that could have occurred in the intervening period. “But ultimately, because it’s part of the contract, it will be a negotiated document that becomes live when the contract is awarded.”

That is the key I feel. The Client should be mindful of that 3rd bucket and endeavour that all 'unknowns' are captured to the fullest extent possible.