During the planning and construction of European Road E18 in the south east of Norway, various challenges related to environmental issues have emerged. The total length of this sectionof the highway is 70 km, which has been divided into nine different sections during the development. Two of the sections are under construction, one is still in the area development planning phase, and the six other sections have been built. Some of the environmental challenges concern the building of a bridge over a protected watercourse inhabited by many aquatic species, and crossing a bog inhabited by several endangered species of dragonflies. This paper aims to explain the background and the measures taken to reduce any negative effects on the environment during construction and in the operating phase of the highway for the two examples given. The first example involves building a bridge over a protected watercourse. The river also has an outlet to a lake that is a major drinking water source. Additional challenges in the area include severe ground conditions with quickclay. The area is also very vulnerable to flooding, which occurs frequently during the year. Because of the quick clay, bridge foundation to bedrock was necessary, which induced the need of piling a total of about 3000 m. This again led to large amounts of drilling fluids (suspended solids) in the piling process. To prevent the drilling fluids from contaminating the river, a large treatment plant was set up using chemical precipitation and sedimentation for the removal of suspended materials. Extensive monitoring of the water quality was performed before, during and after the work. The results show that the piling work did not significantly affect the water quality in the recipient;thus, the measures used worked as intended. Another challenge encountered in the project was the building of a bridge across an area inhabited by many speciesof dragonflies, including some endangered ones, through a bog area. The main measures included increasing the length and height of the bridge to ensure enough space for the dragonflies to move around. During the construction phase, the peat bog was removed. It is currently being stored and will be returned to the area under the bridge after the construction is finished. This work is still ongoing, and thus no evaluation of the work has yet been carried out.
bridge construction; environmental challenges; drilling fluids; water quality; dragonflies