There were few difficulties building the line in the relatively flat landscape between Drammen and Larvik. The largest challenge was building through Kobbervikdalen. The navvies were uncomfortable building a cutting south of Holmestrand, where the line went through an old cemetery in clay ground and they would often find well-preserved corpses while digging. The section between Larvik and Skien went through considerably more hilly terrain, especially along the shore of Farrisvannet, which included more than twenty tunnels along a section of . At the peak, in 1879, there were 2,114 people working on the railway construction, receiving an average NOK 2.50 per day in wage.