CMT Copenhagen Metro Team – WEBUILD Group

Benzene is a highly volatile hydrocarbon, colorless and highly flammable with a sweet smell. It is highly toxic and carcinogenic. Concentrations up to 40mg/lt in water samples were detected south of the TBM launching shaft called Sønder Boulevard, affecting 300m of tunnel alignment for both TBMs on their route to København H station. Mining in benzene contaminated ground and the associated implications and risks entailed a series of challenges (schedule, environmental) the main however was to ensure the health and safety of the TBM operating personnel, both underground as well as at surface. The risk of benzene release into the tunnel while bringing the muck from the excavation chamber to the service trains and later on to the portal was high and present at several locations and mining processes: excavation chamber, screw conveyor discharge, back-up belt conveyor and the train muck boxes. A series of innovative technical solutions were designed and implemented on the TBM parts and systems to mitigate the risk of benzene release: - Direction of the excavation chamber air discharge to the muck conveyor sealed enclosure - Water collector at the conveyor belt sealed enclosure connected with sealed tank - Fume extraction system at the screw conveyor discharge point as well as the erector area - Extension of belt conveyor to eliminate mobile/reversible conveyor parts - Sealed enclosure of the conveyor belt along the entire back-up - Forced air extraction along the covered/sealed conveyor belt - Fire retardant and foam sprinkler system on top of the service train muck boxes - Muck box covering system immediately after loading - Sealed TBM control cabin The technical improvements on the TBM equipment were combined with a dedicated monitoring plan in accordance with the limits and regulations recommended by the local authorities. Moreover, special PPE was made available on the TBM: full face masks with filter and fully sealed protective suits. Specific training of the TBM crews on the new procedures and equipment was conducted and relevant emergency drills took place before and during the excavation of the contaminated stretch. In the absence of previous record of TBM mining in benzene contaminated ground, potential failure or insufficiency of the mitigation measures would not only compromise the safety of the operating personnel but would also put at risk the project time schedule and economy at large scale. Therefore the confirmation of the validity of all relevant considerations and calculations and of the effectiveness of the innovative and widely bespoke mitigation measures applied was of paramount importance. The eventual execution of the excavation without delays to the time schedule and – much more important – with zero accidents due to contaminants’ propagation is unambiguous evidence of correct assessment of all risks along with effective definition and implementation of innovative mitigation measures to ensure the health and safety of the operating personnel.

This category rewards innovation that is boosting productivity, safety or quality in the design and construction of tunnel shafts, the construction process of tunnel linings, and the excavation process of a tunnelling scheme through new products, equipment or methods. The innovative product, equipment or methodology must have been used on a specific project and be able to demonstrate benefits to the overall project outcome and have delivered greater client satisfaction.

VINCI Construction Grands Projets is a subsidiary of VINCI, a global player in concessions and construction, employing more than 211,000 people in some 100 countries. The mission of VINCI is to design, finance, build and operate infrastructure and facilities that help improve daily life and mobility for all. Following on from successful projects, VINCI Construction Grands Projets London office was established in 1992 to ensure the development of local long-term UK partnerships. Established for more than 25 years, VINCI Construction Grands Projets is involved in the construction of major civil engineering structures with key customers.