GSTT (German Society for Trenchless Technology) has been operating for more than 20 years and has been supporting this technology at trade fairs, conventions and in presentations, as well as beyond the German border. The Berlin Water Utility, or Berliner Wasserbetriebe (BWB), already conducts 50 per cent of all renewal projects in the sewer and pressure pipeline system using Trenchless Technology. The Germany-wide average in renewal projects is 10 per cent, with an ongoing upward trend.

Automatically controlled pipe jacking was established over 25 years ago in Berlin. In June 1984, Berliner Entwässerungswerke – now called Berliner Wasserbetriebe (BWB) – started the world’s first fully automated pipe jacking with a nominal width of 250 mm. This innovation revolutionised the sewer pipe construction and has now become a standard construction method in sewer and pipeline engineering.

The ‘Berlin construction method’ or the radial positioning of connecting sewer pipes towards the starting, target and auxiliary manholes using the trenchless construction method, was designed and introduced by BWB along with the development of controlled house service connection systems as early 1984, and was the final breakthrough of trenchless construction.

For years, tunnelling methods had been used for the construction of accessible underground services with economic success. For non-accessible pipe cross-sections, however, the changes in sewer construction had mainly been limited to the mechanisation of building site operation, soil excavation and the introduction of new installation methods for retaining walls.

Fine preconditions in Berlin

In 1984, some 74 per cent of all sewer pipes in Berlin (West) ranged within a nominal width of <400 mm. At that time the trend that the main field of application for closed construction methods would range within a nominal width of up to 400 mm was already evident. These requirements were met by the pipe jacking system RVS 100 A (Soltau GmbH), applied for the first time. This system was laid out for pipe jacking using nominal widths ranging from DN 250–400 mm and was designed to enable pipe jacking from manholes with an internal diameter of as little as 2,000 mm.

Rapid technological development

The development of pipe jacking continued at a breathtaking pace. The pipe eating method, first tested in 1987 at a construction project in the South of Berlin, now also provided a solution for the underground renewal of defective sewer pipes. Driving systems were developed for small nominal widths along with machines using auger boring. A house service connection system was placed on the market in 1987, which enabled remote-controlled trenchless connections to existing main sewers for the first time.

In 1996, there was another economic breakthrough in the history of microtunnelling. Whereas, the technology available until then only allowed a trenchless renovation of sewers of a nominal width of no less than 250 mm, another innovation also enabled the section-wise renovation of sewer pipes of a nominal width of 200 mm.

Over the last 13 years, BWB has saved some €15 million of construction costs by reducing the nominal width from DN 250–200 mm, which could be spent on other construction projects.

This innovation, however, did not exclude the so-called ‘accessible’ nominal width range. So far, pipe cross-sections up to a dimension of DN 3,000 have been excavated unmanned with the microtunnelling technology in Berlin. In autumn 2009, a tunnel was driven under the shipping canal in Neukölln, facilitating reinforced concrete jack pipes of a nominal width of DN 1,600 mm, using the method of unmanned pipe jacking.

Savings and environmental protection

More than 780 km of collective and house service connection sewer pipes were constructed using Trenchless Technology in approximately

26 years of microtunnelling in Berlin, saving a total of €67 million of construction costs that could be invested in other construction projects, and avoiding the excavation of 2.4 million m3 of soil.

Other negative impacts avoided included:

• Digging up and restoring 1.3 million m2 of road surface
• Transporting 198,000 truckloads of soil through the city
• Extracting 212 million m3 of groundwater (equal to Berlin’s yearly water supply).

A comparative calculation of GSTT showed that the CO2 emissions of the construction equipment used in the open construction method was

267 per cent higher than that of the closed construction method.

In more than 25 years of microtunnelling in Berlin, over 4,200 trade visitors from all over the world have visited the Berlin sewer pipe construction sites and got to know the successful application of laser-controlled and computer-assisted microtunnelling engineering during these trade fairs.

Berlin and the trenchless replacement of pressure pipes

The trenchless replacement of pressure pipes without vibration and without leaving the remains of the old pipe in the ground was developed in Berlin in the mid-1980s. The Berlin Government was looking for new sources of capital and passed a regulation to pay a levy of €5.00 per metre per year to the Senate of Berlin for pipes that were not used by the utilities.

Around the same time, it enacted a new regulation for the protection of trees, banning digging under treetops. Berlin has the most roadside trees of all cities in Germany, both in relative and in absolute numbers. Viewing the cross-section of a road, water pipes are located directly under these trees. As a consequence, there is no way to replace the pipes using open construction. Another factor was that it was not allowed, for environmental reasons, to leave any debris of old pipes in the ground. Furthermore, due to the density of adjoining pipes, it was impossible to use any method if it caused vibrations.

Due to these requirements, construction companies in Berlin developed various methods to adapt. Two methods, Hydros and Hilfsrohrverfahren (auxiliary pipe method), have proven practical and appropriate for construction sites. The methods are used to replace more than 30 per cent of pressure pipes for potable water in Berlin, simultaneously and vibration-free, without leaving any waste in the ground.

Capital of trenchless technology

Professor Jens Hölterhoff, Hochschule Wismar and Chairman of GSTT, welcomes the constantly growing popularity of trenchless construction projects.

“Berlin as a vanguard, as a ‘trenchless capital’, points the way ahead for an entire country. The huge advantages of ecological and economical construction methods are being more and more recognised and actions are being taken accordingly, both here in Berlin and in the rest of Germany. We are on the right track,” Mr Hölterhoff said.