Assessment of the effect of an action or project on a local or regional environment. A formal requirement for certain classes of projects in many countries and with specific analysis requirements.

Particular type of Environmental Impact Assessment carried out in the European Union.

Swing arm on boring machine or shield, used for picking up supports and setting them in position.

Gases from engines, pollutant emissions.

Equipment installed in all diesel vehicles working in underground works. It depurates gases from engines.

A tunnel driven before the tunnel design is finalized, to obtain information about the ground, its behaviour and ground water characteristics

A shaft constructed for the purpose of studying ground conditions in the vicinity of a future underground opening.

A device for precisely measuring the convergence or divergence of reference points along a common axis.

An effect or cost of a project or action that is real but is not of direct interest or concern to the decisionmaker involved. Also called "externality".

See external effect / cost

Additional payment made to a contractor as a result of work or use of materials beyond the scope of the original contract.

The exterior surface of an arch. In a tunnel, it is the arch surface lying against the excavated rock or soil surface.