Norrköping is a city in the province of Östergötland in eastern Sweden; the city sits by the mouth of the river Motala ström, at Bråviken, an inlet of the Baltic Sea.

Relining the pipes solved the problem for the municipality of Norrköping. The costs and energy expended by pumping were both reduced. The pay back time for the whole project was less than two years. Furthermore the project was awarded the SSTT No-Dig prize for project of the year.

Norrköping Vatten (NOVA) is a company owned by the municipality of Norrköping. The company is responsible for all water supplies and for the operation of more than 180,000 kilometres of buried pipes. Part of the pipe system runs under the old harbour of Norrköping, in the Bråviken inlet.

NOVA Engineer Helena Aspdahl, responsible for the harbour project, said “We noticed as soon as the water in the Braviken was rising, the pump energy was rising too. In the end, the two big sewer pumps we have in this part of the system were working all day and all night.”

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It became clear that water from Bråviken was infiltrating the pipes. Following CCTV inspection of the pipes NOVA discovered several leaks. The leaks in the pipe that runs under the harbour were small but numerous.

It was obvious that the pipe system was in need of a renovation and the choice was between digging a trench in the traditional way, or use modern Trenchless Technology.

“Digging a traditional trench, replacing the pipes and backfill would be very complicated and problematic because sometimes the pipes run under the water level, surrounded with badly chosen backfill, soil and clay, which also makes the risk for subsidence very high. On top of that, there are a large number of other pipes in the area, and this means that excavating is a risk of its own,” said Ms Aspdahl.

In late 2008 Norrköping Vatten contracted Aarsleff Rörteknik AB – a well known supplier of Trenchless Technology – to solve the problem and renovate the pipes in the harbour of Bråviken. Choosing the Aarsleff cured-in-place-pipe (CIPP) technique made it possible to avoid the problems with the soil, mud and the other pipes running nearby. A calculation and comparison also showed that the price, in total, would be less expensive. The 945 metres of broken pipe, in various diameters, was relined in less than a week.

Following the completion of the project the actual time spent pumping the sewage was reduced to less than 6 hours for every 24 hour period. The leaks amounted to 300 million litres of water every year, equivalent to a cost of 900,000 Swedish kroner (SEK) ($US121,670) per year in electricity. The high volumes were occurring approximately 100 days of the year. The cost in order to purify this quantity of water, was 300,000 SEK ($US40,578) per year, which in total adds up to an annual saving of 1.2 million SEK ($US 162,258).

“The expectation is to have the project reach the payback time in less than a couple of years, which in my opinion is very good,” said Ms Aspdahl.

The environmental profits, the short payback time and the strategic way in which Norrköping Vatten together with Aarsleff Rörteknik completed the project, is also the reason why the small project in the harbour of Bråviken was nominated and awarded the best Scandinavian No-Dig project for 2009.

The competition is arranged by Scandinavian Society for Trenchless Technology (SSTT) and the prize is given for the best trenchless project during the year in Scandinavia. Aarsleff Rörteknik was also involved in the No-Dig prize for 2008, a 440 metre relining project of a 1,800 mm diameter concrete tunnel using the segmental GRP lining technique.