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No-Trench Microtunneling Method

The Breitenrain Sewer System Rehabilitation project in Bern involved replacing the aged sewer systems in Viktoriastrasse and Moserstrasse. The project utilized a no-trench microtunneling method with DN 1,200 pipes, totaling 1,215 meters of microtunnel constructed over seven sections. Thirteen excavation pits were created to serve as start and target shafts for the microtunneling, and subsequently for constructing sewer shafts. The excavation pits varied in depth from 6m to 8m, secured by different methods depending on the location.

Utility Relocation and Prefabrication

The project saw the relocation of existing utility lines and included prefabricating nine out of twelve shaft structures, with the largest prefabricated structures weighing up to 62 tons. This prefabrication significantly reduced the duration during which pits remained open, minimizing the impact on traffic and pedestrians. Challenges included managing traffic with public transport, normal traffic, pedestrians, and cyclists in tight spaces, along with groundwater occurrences.

Safety Measures and Costs

Safety was prioritized due to the deep excavation pits, employing shaft ladders with back protection. The project was executed in joint venture by Implenia Switzerland Ltd and B+S AG, with construction starting in May 2016 and completing in June 2018. The total cost of construction services was valued at 14.1 million CHF, with the Tiefbauamt der Stadt Bern serving as the building owner.