Repairing a sewer, while saving the trees

Trelleborg - Case Study - Repairing a sewer, while saving the trees


B. Braun, a large producer of medical products, operates a facility and wastewater treatment plant in a woodland park that is part of a delicate regional ecosystem. When a CCTV-inspection of the pipeline showed that 1000 feet of pipeline had been damaged by encroaching tree roots they wondered:

How do we rehabilitate a badly damaged wastewater system in a dense forest with steep inclines, while preserving natural resources?

The sewer to be rehabilitated was a vitrified clay sewer (DN 150) carrying a permanent flow of treated water from the wastewater treatment plant to a receiving body of water. Braun decided to rehabilitate 325 meters of this sewer (14 sections with 15 manholes) damaged by encroaching tree roots. However, access to the sewer was limited as it was located in a dense forest and on an incline without vehicular access.

Our activities

tkm-Service GmbH oversaw the project and met with an expert from Trelleborg Pipe Seals to find the best solution to deal with the forest’s limited access and steep inclines. Trelleborg advised the use of their DrainFlexLiner and HC120+ resin for hot water curing.

The resin’s generous pot life allowed the crew over three hours to prepare the liner, carry it down the hill using large wheelbarrows and invert the liner into the manholes. Purpose built water towers let the steep hill and gravity work to their advantage. While three teams worked themselves into a sweat, the resin’s pot life was a huge value to tkm’s efficient workflow.

Trelleborg’s DrainFlexLiner was recommended as its longitudinal fibre reinforcement prevents it from overstretching in inclined pipe sections with higher water pressure at the lower end.

After the liner cured, a leak test and CCTV inspection were performed. A liner sample was sent to a laboratory for further testing and the findings were extremely positive: the cured liner was 100% watertight and the mechanical values exceeded normal requirements. An environmentally friendly solution as Trelleborg’s resin contains no VOCs or styrene. Best yet: not a single tree was felled. Pipe fixed – nature preserved!

Product details

Trelleborg’s DrainFlexLiner, made out of polyester needle fleece with a polypropylene coating, is highly elastic and available in different wall thicknesses.

Trelleborg's HC120+ epoxy resin was recommended because of its extremely generous pot life, short curing time and high mechanical values. It contains no VOCs or styrene, making it safe for the environment and workers alike.

The resin’s ample pot life, over three hours, was of particular value to this project due to the challenging terrain. The crew thus needed time to mix the resin, impregnate the liner, transport the resin-impregnated liner by hand through the trees to the entry-manhole, and invert it into the sewer before curing could begin.