In 2010, the sewer cleaning contractor, Woitas Rohr- und Kanalreinigung, from Apolda was awarded a tender contract to repair and renew sections of a wastewater treatment plant situated next to a water barrage and power station. The contract also included the rehabilitation of all drainage pipes along the transformer route.
The location of the work site next to the power station meant that parts of the power station needed to be turned off during installation — making the time frame for installation short, with no room for error, as further shutdowns would cost the energy company, Vattenfall AG, money.
This meant that Trelleborg, as the manufacturer, and Woitas, as the installer, needed to work together to execute this project without failure and while being prepared for the unexpected. For this, they turned to the tried-and-tested epros®DrainLining method.
In 2000, an EU Water Framework Directive (WFD) was passed stipulating that all water bodies must meet a “good ecological status” by 2015. The state of Thuringia has thus provided funds to replace and/or upgrade sewage treatment facilities across the region, and in doing do, ensure the biological purification of wastewater.
One such sewage treatment facility that needed work was located directly at the foot of the Bleiloch Barrage’s dam wall.
The first phase of the project was to replace the current treatment facility with a new biological sewage treatment facility as well as renew incoming wastewater sewers. The second phase was to rehabilitate drainage pipes serving the transformer section.
But neither the condition nor the actual route of the drainage line towards the dam wall and the foundation rocks were known. The contract for this project was awarded to Woitas Rohr- und Kanalreinigung, a specialist company familiar with challenging project conditions and who recommended Trelleborg‘s epros®DrainLiner method to the client. They did so because the trenchless rehabilitation solutions by Trelleborg are suitable for many applications: they allow for patch repairs with short liners, are able to rehabilitate complete pipe sections with full-length liners, and are able to seal entire surfaces; depending on which solution is selected.
Made up of carefully matched components that have been tried-and-tested through countless successful installations worldwide, the epros®DrainLiner method is also approved by the German Institute for Construction Engineering (DIBt) and is listed by the German Sewer Construction Quality Protection Association (Güteschutz Kanalbau e.V.).
Roland Woitas, operations manager and certified sewer rehabilitation consultant, had this to say about their recommended choice of method: “We decided to use the DrainLiner method from Trelleborg because it had proven to be extremely reliable in the past. Due to the tight window for installation, a high degree of flexibility was also required – which our past experience with Trelleborg’s system and service showed that they had.”
The Installation Site
The installation site was located 65 metres below the access road and 260 steps below the dam wall. To prepare for the inspection of the pipe line, stringent safety precautions were taken. Although the highvoltage overhead power line next to the pipes had been cut off for the duration of the installation, the site crew had to wear special protective equipment at all times.
The first challenge faced was a question of time and how long it took to transport materials to the installation site. Although the site boasted a freight elevator that bypassed the 260 steps and allowed materials and equipment be brought to the lower level with ease, the final distance between the elevator and the installation site had to be covered on foot.
To reach the start manhole for the liner, the team then needed to pass under two overhead power lines, one of which had to remain operative all times. For safety reasons, it was thus necessary to build a shielded tunnel passage in the form of a Faraday cage. A crew member with relevant electro-technical training also had to be on site at all times to supervise the work and ensure that safety precautions were being met.
The next challenge faced was that it was not possible until the day before the installation to inspect the host pipe run and measure its exact dimensions and condition – making it impossible to estimate the actual extent of the work required.
It was thus necessary to have enough material and manpower on hand, to be prepared for the unexpected.