ITA guidelines for the preparation of the GBR for the NEC4 engineering and construction contracts – Options B and D with bill of quantities

Abstract

This guideline outlines the recommendations of the International Tunnelling and Underground Space Association (ITA) for preparing a Geotechnical Baseline Report (GBR) for the NEC4 Engineering and Construction Contract (ECC), specifically for Options B or D, with use of a Bill of Quantities. This document complements and should be read alongside the “Guidance on NEC and Underground Works (2025)” (hereafter referred to as “NEC-ITA Guidance (2025)”), which provides a model clause and guidance for implementing an alternative risk allocation approach using a GBR within the NEC4 ECC.