Targeted at designers, project managers, clients, contractors and any other parties involved in underground construction or tunnelling projects, it is based on experience gained across a variety of projects and will be applicable to future underground works whatever their scale. Monitoring is a subject of particular importance to underground construction works. It is often a key risk mitigation measure both for the control of the construction process and the protection of existing assets affected by excavations. The subject is treated at the level of key principles, focusing on objective setting, strategic planning and the high level specification of monitoring systems. It aims to help avoid problems, which have in the past arisen due to omissions in these areas. The guide is structured to reflect the key stages in a project. It starts with objective setting and then addresses requirements for system planning, specification, design, operation and management. It also seeks to highlight the roles and responsibilities of the various stakeholders at each stage. Five illustrative case studies taken from a range of projects of different scales highlight the critical role of strategic and well-planned monitoring programmes in the success of any underground construction project. The BTS is a learned society of the British Institution of Civil Engineers (ICE) and has a membership of more than 900 individual and corporate members. It is one of the most vibrant gatherings of professional tunnellers in the world.