Environmental and occupational risk assessment and management in tunnelling and underground projects

Construction is one of Europe’s biggest industries, providing jobs for nearly 13 million people. This represents nearly 8 % of the working population in Europe (only the public sector and retail employ more). It is also one of the most hazardous industries. More construction workers are killed, injured or suffer health impairments than in any other industry, and one of the most critical section in the construction sector is the underground construction. In particular the effect on workers’ health is of serious concern. It is difficult to be precise about the true scale of the health problem, but all studies indicate the problem is huge. Every year many thousands of workers suffer from work related diseases. These include musculoskeletal disorders, noise induced hearing loss, skin diseases, and other diseases as a consequence of exposure to noxious substances. Additionally, the economic costs of poor safety and health are vast. One national study estimates that they typically account for up to 8.5% of a construction project’s costs. The creation of underground space has significant impact on quality of life, working conditions, employment and environment. Innovative use of underground space will have a great impact. European Union policies include an upgrading of the Trans European road network (TREN), in order to improve interstate transport. This implies the construction of a significant number of tunnels (approx. 2100 km of tunnels will have to be constructed in Europe by the year 2030). Underground space will be increasingly used to alleviate pressing problems that will confront the European society in the next 20 years: traffic congestion, increasing urbanization (mega cities), lack of space and pollution of air and water. In Italy, the construction of rail and road tunnels through the Alps and the Apennines is very important in terms of connection and moreover, the requirements of transport systems, for civil use spaces and for innovative service networks is one of the reasons for the increase of underground works in urban areas more densely populated. The hydrogeological, geological, operational and environmental criticalities as met in such geological structures can nevertheless require increased care in the aforesaid situations. Projects under construction have further highlighted the importance of tunnels for the elimination of traditional surface, territorial and environmental constraints, but also for the necessary acquisition of consensus through the most comprehensive analysis and management of risks related to the effective fulfilment of such projects, in order both to meet the needs of the end users, and to preserve the dwellers and environmental safety conditions in terms of correct sustainable development. The most important changes in such a point of view occurred since the end of the last century, and suggest the need of a more effective and comprehensive approach to the concept of infrastructure. For this purpose it is nowadays required a horizontal approach, whereby different disciplines (technical, structural, architectural, environmental, financial and occupational safety) can interact and mutually stimulate in order to face the complex issues of underground works project. For these reasons, the designer's role becomes crucial to develop underground projects that respect a sustainable development approach; designer must know innovative and advanced technologies, materials and procedures, aimed at optimizing the economical, environmental and social development. Even the public client, responsible for government priorities and objectives of the intervention, is fundamental for the orientation of the operational choices of designers and builders of infrastructures. In fact, especially in the last decade, a number of guidelines and recommendations were issued by International, European and Italian authorities, the most effective of them based on the introduction of the prevention in the design phase and on a quality based risk management. The design and construction of underground operations require by the Designer and Contractor/s a decision making based on multiple factors (environmental, technological, etc.) that have specific characteristics and particular criticalities, far more than other industrial contexts, since they are often characterized by considerable uncertainty in their definition during the development of the project. In this context the Designer must identify the best option among several available solutions -which have different implications in terms of technical, operational, environmental and financial risks- while the Contractor/s must make a constant check on the preservation of design conditions, in order to control the validity of work and environmental safety requirements. Furthermore, for maintaining the correct safety conditions, it is of primary importance the application of Hazard Identification Techniques referring to different design solutions, and the definition of suitable confidence limits in order to provide the work manager with suitable instruments to constantly evaluate the yard situation and to avoid the overcoming of the aforesaid limits. The PhD research project has therefore to cover the most common criticalities encountered in tunnelling and underground works projects such as: - the presence of pollutants, and in particular carcinogenic minerals, such as, for example, the crystalline silica, which is recognized class A1 carcinogen (carcinogenic certain to humans) by the International Agency for Research on Cancer -IARC- since 1997 (and reaffirmed by the same organization in 2011) and the types of fibrous silicate included in the formal definition of asbestos, which there is no discussion on the ascription to the class A1; - the design and management of the construction yard: the presence of limited working spaces, the high concentration of high power machinery and the use of iterative work cycles, together with reduced time for the excavation, make mandatory the need to plan the interference among concomitant operations in order to prevent accident; - the control of the safety conditions: it is of primary importance the application of Hazard Identification Techniques referring to the choice of suitable confidence limits in order to make available for the work manager the instruments to constantly evaluate the yard situation to avoid the overcoming of the aforesaid limits and referring to the choice of equipment and procedures to minimize accidents at work. Taking into account the best available techniques, the principles of Quality and Prevention through Design approach, the PhD research has also set criteria for the identification and evaluation of the above mentioned criticalities in order to develop an expert system, finalized to make available an integrated system to optimize the economic, environmental and operational safety for the underground works activities in order to proceed rationally to choose the best solution.