Finnish challenges

In 2003, CCTV inspections showed that one of the largest wastewater pipes in Helsingfors was in an even very poor condition. Approx. 2 km out of the total 9 km of pipe had to be renewed. Aarsleff Pipe Technologies was asked to carry out this complicated job from October 2006 to February 2007. It was the biggest pipe renewal project ever in Finland, and to top it all of it had to be carried out during the cold Finnish winter.

The contract included for example:

• Preparation of the installation pits
• Six excavation places for manholes with a diameter of only 800 mm
• Bypass arrangements
• 2 km of Aarsleff CIPP Lining
• Renewal of 40 manholes with jetcrete
• Renewal of 90 laterals with 1 m long Aarsleff Hat Profiles
• Targeted and extensive information to the residents whose everyday life was affected by the work

Several factors added to the complexity of the project. The financial situation was a special challenge as the damaged pipe received wastewater from two different cities in the Helsingfors area. Add to this the fact that parts of the sewer had collapsed in the spring of 2006.

The greatest challenge was the number and size of the bypass arrangements. The client required a maximum flow capacity of 740 l/s and a solution that caused minimum disturbance to traffic and citizens.

The installation of Aarsleff CIPP Linings and bypass arrangements were done in two sections, each of a length of one km. The pumping station consisted of two suction pumps, each with a capacity of 1200 l/s. The pumping station was operated by one of the pumps while the other was in reserve. The pumps each had a 250 KVA generator and frequency converter.