Rehabilitation of the Wastewater Systems in Spittal/Drau

60 years that is roughly the service life of sewer systems. Why does that matter? When wastewater no longer flows properly, it can escape from the system and contaminants may enter the groundwater. This can have serious consequences for both people and the environment. To prevent this, the municipality of Spittal/Drau commissioned a comprehensive rehabilitation of its wastewater systems.

Precise preliminary work – the key to success
Under the direction of Ingenieurbüro Kronawetter GmbH (now HPC IBK), the entire combined sewer system was first examined, including pumping stations, combined sewer overflow structures and retention basins. This involved not only inspecting the existing sewer network but also measuring flow and precipitation volumes as well as assessing the impact on groundwater and surface water.

The result: significant hydraulic deficiencies had to be addressed immediately. Based on the hydraulic and structural assessment of the inspected sewers, the ecological situation and the possible future development of the system, a comprehensive rehabilitation plan was developed and implemented over a period of almost three years.

Implementation – Following the Path of the Sewers

Leaking and outdated sewer systems were rehabilitated using two different methods. In some sections, underground repairs were carried out using trenchless lining techniques (inliner method), which allow renewal within the existing pipes. In other areas, trenches were excavated and the pipes were completely replaced.

While these tasks themselves posed no difficulty for our experienced specialists, the team faced a very different challenge.

Clean into the Future

After only three years of planning and implementation, parts of the sewer system in Spittal/Drau are now operating like new again. The system has been upgraded to the latest state of the art and is therefore more sustainable than ever before.

No wastewater can enter the groundwater anymore, and in the long term the municipality will benefit from reduced operating and maintenance costs. Once again, our team has demonstrated that we combine technical expertise with a strong focus on sustainability.

The major challenge in this project lay in the extremely limited space and accessibility on site. In the western and eastern construction areas, the new daycare center building directly borders neighboring buildings that are still under construction. To the north and south, the excavation pit directly adjoins public spaces: on one side there is a tartan running track where neither construction vehicles can drive nor building materials can be stored. On the other side, the only access to the construction site is a one-way street with adjacent cycling and pedestrian paths. This means that extensive work, such as excavation, had to be organized under one-way traffic conditions.

This created major logistical challenges, not least when installing the water treatment plant required for groundwater lowering. Since there was very little space available around the excavation pit, the plant was installed 250 meters away on a plot of land where construction had not yet begun. A complex task in whose planning and implementation Ginger HPC was involved. In doing so, we made a significant contribution to preventing contamination of the Elbe River and the groundwater.

In the meantime, buoyancy protection for the new building is ensured by its own weight and additional structural load. As a result, the groundwater management system has been successfully completed and dismantled.

And Now? Moving into the Future with Sustainability

The space along the sides of the excavation pit is available for backfilling. It is planned to fill the southern shoring area, under the professional supervision of Ginger HPC, with flowable fill (liquid soil) up to 1.5 m below ground level. The sandy backfill to be placed above will be flushed in with water. During this process, the timber lagging will be gradually removed.

Finally, the public areas such as roads, pedestrian and cycle paths, as well as infrastructure including sewer lines for wastewater and stormwater, will be inspected through comprehensive elevation surveys, compaction tests and CCTV inspections of the pipelines. GingerHPC plans and initiates the required evidentiary safeguarding measures, carries out some of them directly, and evaluates the results.