Schloss Hubertusburg, once the most magnificent manor in Saxony and the largest hunting lodge in all of Europe, was built in the small town of Wermsdorf near Leipzig in the 18th century. Today it is an important monument of Baroque European architecture. Built between 1721 and 1724 by Elector Augustus II the Strong as a hunting lodge for his son Frederick August, the manor estate was plundered during the Seven Years’ War and attained historical significance as the site of the Treaty of Hubertusburg in 1763. Today, Schloss Hubertusburg serves as an important medical centre in Saxony and has a large adjacent hospital complex.

Since 1998, the old manor house has been undergoing a €22 million restoration by the Free State of Saxony. “The goal is to preserve the estate while making the buildings usable,” says Heiko Zscheile of IBZ, an engineering firm based in Riesa. He is the planning engineer for the restoration project, which includes the rehabilitation of several kilometres of sewers. In March 2009, the Neumarkt-based company Max Bögl was contracted to rehabilitate two mixed-water drains on the premises of the manor house, with a

DN 600/900 oval profile and lengths of 138.5 and 7.5 metres, respectively.

Using the light-curing method

The heritage preservation statutes for the estate also include the sewer network, its pipes, shafts, and manhole covers. For the estate’s numerous 250-year-old, slab-covered sewers of natural stone, this means that rehabilitation is mostly limited to open cut methods involving the insertion of a pipe into the old sewer and filling the ring gap between the old and new pipes with soft mortar. This way, the old system can be re-exposed at any time to investigate the original architecture. However, in the section to be rehabilitated by Max Bögl, the old slab-covered sewer had been replaced with an oval-profile pipe 80 years ago, which allowed the permanent lining of the old pipe.

The damage was characterised by root growth and cracks, encrustations at the joints, and leaking collars. Because the sewer is up to five metres below ground and runs close to and sometimes underneath buildings, the tender for the rehabilitation specified the use of trenchless methods. According to Mr Zscheile, this was a convenient solution. The shape of the existing pipe was still very good, its hydraulics were evaluated to be sufficient for future use, and the reduction in cross-section – very minor with light-curing liners – was not a significant factor.

For the Hubertusburg project Max Bögl used, for the first time, the new BLUETEC curing technology by Brandenburger. “The opportunity to install our first liner with the new system at this historical location is something special for us,” says Tino Funke, site manager for utilities and waste disposal at Max Bögl.

As a Brandenburger partner, the enterprise relies on light-curing glass-fibre reinforced liners (GFRP) by the German manufacturer. Since September 2008, Max Bögl has installed more than three kilometres of liner ranging from DN 150 to DN 900.

“We investigated the market and concluded that UV curing is the technology of the future,” says Mr Funke. “With UV technology, there are no problems with quality or during the installation itself. The curing is significantly faster than with other processes. Another big advantage is that, with the camera built into the light chain, you can inspect the final product even before the curing starts, while pulling the light chain through the sewer.”

Mr Funke says that the key factors for the decision to partner up with Brandenburger was because the company is a vendor of both the equipment and the materials, offers support, and continuously develops its know-how. Liner installation

The project required very detailed planning and co-ordination. All work had to be performed without any interruptions to the operation of the hospital, and the access road near the installation shafts had to be kept free for rescue vehicles. Also, the liner installation had to be co-ordinated with ongoing construction and civil engineering projects.

In a preparatory step, ways of access were determined, dimensions and distances were measured, and water drainage requirements were identified. Since the majority of the buildings are not yet in use, most of the water was surface water from the manor roofs. The preparations for the inliner rehabilitation also involved work in the sewer. Roots and sediment had to be removed and offset between pipe sections had to be straightened to create a clean cross-section.

“The sewer has a gentle S shape,” says Mr Funke, describing the special technical challenges for the installation of the first, long section. A key factor was the precise adaptation of the curing device with special wheels for this oval profile, in order to keep it at the centre of the sewer and ensure a uniform curing process. The GFRP liner had been manufactured at the Brandenburger facilities in Landau and pre-impregnated with light-curing polyester resin. It was delivered ready for installation and pulled into the sewer directly from the lorry via a conveyor belt. After the first packer had been installed and the liner had been pressurised with air, the curing device with the light chain consisting of nine UVA lamps at 1,000 kW each was inserted. At the lowest point, the second packer was installed.

After the ignition of the light chain the entire section was cured in approximately four hours at a speed of about 60 cm per minute. The final wall thickness calculated in a stress analysis was 7 mm. Immediately after curing, the eight inlets were cut open, and the liner was sealed to the shaft with epoxy resin. The next day, the shorter section was rehabilitated using the same method. A TV acceptance inspection conducted the following week confirmed the successful rehabilitation.

After a review of the delivery documents, the rehabilitation project was completed to the satisfaction of the client, the Staatsbetrieb Sächsisches Immobilien- und Baumanagement (Saxonian Real Estate and Construction Management, Public Company).

Mr Funke says “The biggest benefit is that all key parameters like curing speeds, etc., are recorded automatically in a log. This is especially important in times of increasing quality requirements. Another practical benefit is that the site set-up is relatively simple.”

Planning engineer Mr Zscheile says “The inliner method enables us to perform a permanent rehabilitation extremely quickly and cost effectively. Using an open cut method would have increased costs several times over, and taken much longer too.”