It is well known that the ageing process of pipelines is accompanied by increasing damage. This also leads to massive disposal problems. While repair methods offer only a temporary solution, complete trenchless renewal using the pipe bursting method offers a permanent solution that also enables the modernisation of sewer networks.
Sewer rehabilitation is a pressing issue in many countries around the world. In Europe, too, many sewer systems are outdated, leading to wear and tear, leaks, blockages and other damage. In addition, many wastewater systems are no longer efficient enough to meet today’s demands. Increasing population, urban growth and climate change are also driving the need for upgrades.
Combined Sewers Ideal for Modernisation
The problem is particularly evident in the combined sewer systems that are widespread across Europe. In addition to wastewater from households and industry, they also collect rainwater. This is not normally a cause for concern, as both end up in treatment plants. The problem arises when wastewater leaks into the ground or when the inflow exceeds the capacity of the pipe system and treatment plants. The latter happens when more rain falls than the pipes can absorb. To prevent the rainwater/sewage mixture from backing up, it is collected in overflow basins or, if these are full or non-existent, discharged untreated into inland and coastal waters. The situation is exacerbated by the increasing frequency of climate-related heavy rainfall events. In England, for example, such pollution from overflowing, outdated combined sewers has been making headlines for years. As well as repairing leaks, here it is also necessary to increase the hydraulic capacity of the pipes.
Combined Sewer Replacement In A Recreation Area
In Germany, combined sewers also account for the largest proportion of the total length of the sewerage network, at 40.7%. The condition of the German sewer network is not bad by European standards, but around 20% of all sewers in Germany are in condition classes 0 to 2, which means that they need to be repaired or replaced in the short to medium term. This was also the case in the town of Springe, where a damaged combined sewer of DN700 was in urgent need of rehabilitation and modernisation. The solution was a complete renewal of the affected section using the static bursting method.
The ‘Volkspark’ in the town of Springe is an important recreational area. Very old trees characterise the atmosphere of the park, which has been in existence since the 1950s and offers ideal development and living conditions for animals and plants. There is also a playground and a miniature golf course. Although the park has undergone many changes as the city has developed, with areas being removed and new ones added, it remains an important focal point and a popular meeting place for the local population.
A DN700 concrete combined sewer in this area, built in 1990, had many cracks and fissures as well as significant root ingress, which meant that sewage was leaking into the ground. On behalf of the town of Springe, it was therefore to be renewed in two sections over a total length of 265 m using the bursting method. The pipe diameter of 700 mm could not be reduced due to the required hydraulic capacity. A polyethylene pipe OD800 x 47.4 mm made of PE 100 RC was selected as the new pipe, which was joined to the pipe string by butt welding.
The bursting process was carried out using TRACTO’s GRUNDOBURST 1900G and a 920 mm diameter burst expander, which broke up the old pipe and pulled in the new pipe directly behind it. To avoid overstressing the new pipe, the pull-in process was monitored and documented online by a GRUNDOLOG III tensile force measurement system. After all, pulling forces of up to 190 t were involved! The compact GRUNDOLOG system offers easy handling on site and works with four different measuring bodies depending on the diameter. This gives it an extremely high accuracy of 0.1% of nominal. The data can be
checked immediately on site and stored as a report for the contractors use or as
evidence for the client.
The project was carried out by RETTBERG GmbH & Co. KG of Göttingen, Germany, which has 23 years of experience in trenchless pipe rehabilitation. The company has been working with TRACTO for around 50 years and currently has four GRUNDOBURST systems of different sizes in its fleet, with which Managing Director Karsten Rettberg is very satisfied. This was also the case in Springe, where the old, displaced combined sewer was easily replaced with new OD800 mm PE pipes.
The Bursting Method – Sustainable and Proven
The static bursting method, which has been tried and tested for decades, ensures the sustainable renewal of existing sewers and water mains, as today’s materials have a service life of 80 to 100 years. There are no consequential costs due to subsidence, damage to roads or impact on groundwater. At the same time, the pipe diameter can be increased by inserting larger pipes if more capacity is required.
The powerful GRUNDOBURST models from TRACTO allow pipe renewal up to a diameter of 1,200 mm. The special Quick-Lock rods not only lasts longer than screw-in rods, it is also resistant to pulling and pushing and can even negotiate bends. An extensive range of accessories ensures that all old pipe materials and even pipe sections that have already been rehabilitated with hose liners can be renewed. By measuring the pulling forces during the pull-in process, the new pipes are not overstressed by the strong bursting supports, so the work can always be carried out safely and reliably. Depending on the diameter of the pipe to be renewed, the possible pipe lengths and the location of the site, there is a suitable machine type for every application situation, for example, when a sewer or pipe needs to be renewed from pit to pit, from pit to manhole or vice versa, from manhole to manhole or from pit to cellar when replacing a house connection.
Irrespective of the type of pipe to be rehabilitated and the general conditions, the bursting method offers the most sustainable solution for pipe rehabilitation. The advantages, especially compared to trenchless repair methods include:
- Completely new, load-bearing pipeline with new service life in the
existing route - Can be used for almost all types of damage, existing and new pipe
materials - Sections already rehabilitated with pipe liners can be renewed
- Capacity adjustments are easily achieved by pulling in larger pipes
- No consequential costs due to subsidence, groundwater impact
- No installation errors, high installation quality, high compliance with
regulations - Intelligent, space-saving machine technology
- Manageable equipment and accessory requirements
- Easy and fast to use (high daily output)
As the most sustainable method of pipe rehabilitation, pipe renewal using the bursting method not only enables the permanent restoration of functionality, but also the simultaneous modernisation of pipelines. On the client side, the investment required for the rehabilitation is significantly reduced, as the method allows much larger pipe sections and diameters to be rehabilitated in a shorter period of time. Contractors working in or wanting to work in the pipe rehabilitation sector can tap into great potential for the future by using bursting technology, especially as the versatile pulling rigs can also be used for rehabilitation processes such as relining, calibre bursting or tight-in-pipe
methods.
