Good results in the pre-study before the construction of the West Link

Project Olskroken is one part of a much larger regional infrastructure strategy, which also includes the rail connection through central Gothenburg known as the West Link.

During the construction of the West Link some of the existing properties along the current railroad line will be demolished or rebuilt, and electrical wiring will be reconstructed. The Swedish Transport Administration also builds a new electrical substation for the train traffic at Olskroken.

At the same time, PEAB, which is one of the leading construction companies in the project at Olskroken, explores new technologies for managing and treating storm water in the construction area. In November 2016, a preliminary study was commenced at Olskroken.

– We have considered different methods and techniques, but are in need of a simple solution that doesn’t need large amounts of project space and is easy to integrate into our production. Therefore, the choice of using Swedish Hydro Solutions’s unique water treatment technology was made, a choice that the Swedish Transport Administration also endorse, said Margaretha Ringström, block manager of Time Critical Works at Peab.

A challenge to manage incoming stormwater

The first challenge in the project was to handle the large volumes of stormwater collected in the construction area. During periods of heavy rain, both the ground at the construction site, as well as excavated shafts, can be filled with large amounts of stormwater, which then will create a bottleneck in the treatments systems that handle the stormwater.

– Usually we fill an entire sedimentation container with stormwater in one day. But If It rains a lot, that volume will increase quickly. That is why we need to have water treatment equipment that is able to manage the rapid changes in the volume of water.

Furthermore, the treatment system need to be easy enough to operate that one of our coworker are able to handle the whole treatment process, says Margaretha Ringström.

The next challenge in the project is to reduce the contamination that is present in the incoming stormwater at the site. Lead, arsenic, copper and mercury are some of the heavy metals that are both naturally occurring in the soil, and they also exist as residues in the surrounding ground because of earlier industrial activities at the site.

Suspended particles in the storm water, such as soil and clay, as well as various types of organic compounds also contribute to the problem with stormwater contamination.

Environmentally friendly process with strong results

With Swedish Hydro Solutions’ solution, the water at the Olskroken grade‑separation project is treated to meet the City of Gothenburg’s guideline values for stormwater. This means the water could have been returned to the stormwater system.

– We hope that the Environmental Department will eventually allow us to discharge the treated water into the system. It feels unfortunate to let it run onto the ground only to become contaminated again. But for now, we have to settle for infiltrating it as best we can, says Margaretha Ringström.

She is particularly pleased that the treatment process can be carried out without adding any hazardous chemicals.

– In times like these, environmental awareness is extremely important, especially when treating water that is already polluted. It feels good to be able to treat it in the most environmentally friendly way possible.

Considers more cooperation in the future

With the strong test results from early in the year, Peab is increasing the volume of water treatment, extending the test period throughout 2017.

If the full test phase for the West Link project proves successful, additional stakeholders are lined up to test chitosan‑based water treatment.

– We have had a visit from NCC, who are interested in how they can manage water volumes in tunnels and excavations around the central station. These are areas where you really do not want water to accumulate, says Margaretha Ringström.