New guide on using NEC4 ECC with geotechnical baseline reports

In June 2025 NEC published a new 24-page guide on how to use the NEC4 Engineering and Construction Contract (ECC) for underground works with a geotechnical baseline report.

Prepared jointly with the International Tunnelling and Underground Space Association (ITA), Guidance on NEC and underground works enables a geotechnical baseline report to trigger compensation events for defined physical conditions instead of the standard NEC4 ECC clause 60.1(12).

ITA wanted its members to be able to use NEC4 ECC with geotechnical baseline reports as an alternative to using the Fidic Conditions of Contract for Underground Works (2019 Emerald book). The approach is specifically suited to NEC ECC4 Options B (priced contract with bill of quantities) and D (target contract with bill of quantities).

The guidance, which is free to download from the NEC website, provides a set of model Z clauses to effect the change. These include a mechanism for assessing delays to the completion date and amounts for time-related cost caused by changes to key tunnelling quantities.

The guidance also includes model contract data entries and advice on preparing a geotechnical baseline report.