What "buttonhole surgery" with the famous "bikini sutures" is for the surgeon, is for the Vienna Waterworks the trenchless laying and renovation of drinking water mains. Through innovative technology the federal capital Vienna has achieved an excellent internationally renowned drinking water quality. To keep this standard, the Vienna Waterworks (Municipal Department 31) not only have to guarantee the safeguarding of natural resources, but also to constantly repair and renew the local mains.
Vienna's water pipeline has a length of about 3,200 km, diameters range from 80 to 1,200 mm. Nearly 100.000 objects are supplied by service pipes of a length of 800 km. "In view of this figures it is not astonishing that a considerable part of budget means is being allocated for the repair and renovation of the supply network", explains Dipl.-Ing. Hans Sailer, head of the Vienna Waterworks. In 1998, for example, 31,000 metres of pipes and 2,600 pieces of service pipes had to be replaced or newly installed. "About 36,34 million EUR were spent that year for renovation and replacement of mains", Sailer continues.
Rehabilitation and maintenance works in the capital Vienna affords high expenditure and social constraints caused by the necessary digging works. "The problems are not only the noise and dust but also traffic obstructions and less space for pedestrians", describes design expert Dipl.-Ing. Franz Weyrer the problem of renovation.
The Vienna Waterworks have therefore been relying on no-dig construction techniques that offer various advantages such as:
- less digging
- saving of natural resources (no backfilling)
- less construction noise
- less dust
- less construction site traffic
- shorter construction period
- less expenditure
Smaller pipe diameters and local mains have been installed for many years in no-dig technique. "About two third of service pipes in Vienna are totally or partly installed by the directional drilling technique", Weyrer explains. "For precisely underpinning installations in operation we are increasingly using controlled thrusting and drilling methods", explains the expert of the Waterworks. A remote sensor on the street surface locates the position of the splaying head so that it can be adjusted if necessary. Trench digging on sidewalks can be minimised by using collar pipes, by placing isolating valves in the cellars and in the barrel.
In pipe diameters of 80 to 200 mm the pipe extraction process is increasingly used. The old grey cast iron pipes are extracted from the ground by a powerful traction press and destroyed. New tensionproof interlocked pipes are immediately pulled into the empty hollow space. This procedure can be used under confined conditions. Using this method about 2 km of pipes were replaced in the past few years. (Source: aqua press Int. 4/99)
Renate Haiden
Information & Contact:
Vienna Waterworks - Municipal Department 31
Dipl.-Ing. Franz Weyrer
Grabnergasse 4-6,
A-1060 Vienna
Phone: +43 1 599 59-94421
Fax: +43 1 599 59-7231
