Risk reduction for underground works 09 May 2019

Underground space for infrastructure is in increasing demand, but during construction it can be difficult to predict ground behaviour. The uncertainty gives rise to contractual risks regarding construction practicability, time and cost, and the geological, hydrogeological and geotechnical properties of the ground determine the methods required for successful implementation of works.

The Emerald Book contract

To address this issue, International engineering federation FIDIC (the International Federation of Consulting Engineers) and ITA-AITES (the International Tunnelling and Underground Space Association) have teamed up to publish a new form of contract for tunnelling and underground works, The Emerald Book.

The book, which was launched at the World Tunnel Congress in Naples this week, addresses risks and is recommended for use in all underground construction projects. The launch follows several years of intensive work by a joint task group of representatives from FIDIC and ITA-AITES who identified several issues that the contract should address to promote equitable risk allocation and the effective dealing with conditions typically unforeseeable in such projects.

These issues include the following, all of which are specifically addressed in the new contract.

• Allocation of risk
• Disclosure of all available geological and geotechnical information
• Inclusion of a contractual geotechnical baseline
• Inclusion of a tailored “Unforeseeable Physical Conditions” clause
• Implementation of a ground classification system and of supporting particular conditions that properly reflect the effort of excavation and stabilisation
• Time for completion to be largely influenced by ground conditions
• Provision of a flexible mechanism for remuneration according to ground conditions, foreseen and unforeseen

Guidelines will help anticipate risks associated with works

With the increasing need for underground works for energy, transportation and urban infrastructure as a result of space shortages in cities due to population growth, take-up of the new Emerald Book contract is expected to be widespread.

“Working together, FIDIC and ITA-AITES have created a contract that we believe, and hope will command the respect and authority of the tunnel engineering and construction sector that both clients and contractors can use with confidence. The new Emerald Book addresses several critical areas that should lead to the smoother running of contracts in the growing tunnelling and underground works sector,” said Zoltán Záhonyi, FIDIC contracts committee chair.

“The Emerald Book will bridge an important gap. Despite all the technological developments of equipment and techniques in the field, many underground construction projects end up unsuccessful because of contractual disputes. The book brings together the result of the expertise and respectability of ITA-AITES and FIDIC in the fields of contracts and specifications for underground construction,” said Tarcisio Celestino, president of the International Tunnelling and Underground Space Association.

The new contract is available for purchase from the FIDIC online bookshop.