Rehabilitation by CIPP liners of a sewer line through the Liseberg amusement park
iMPREG GmbH and their client Avloppsrallarna worked together to deliver this very technical and challenging project on the Sustainable Waste and Water department of the City of Gothenburg. Together we lined 1,120 metres of a DN 1500 mm combination sewer line stretching partly through Liseberg amusement park. Project engineer Antje Koppen from Gothenburg Sustainable Waste and Water commented ‘It was a difficult and unique project for both of us, we learned a great deal during the procurement process and implementation of the project.’
The history behind the project is that Gothenburg have been experiencing high volumes of groundwater ingress in its sewer lines, so consequently is actively working to remove the leakage problem. The ten-year mean value for groundwater ingress in Gothenburg is 57 % and the current mean value in the action plan is 50 %.
The current section of the project is within the Kodammarna pump station drainage basin where roughly one-fourth of the waste water from Gothenburg is pumped to the Ryaverket purification plant. The main flow is approximately one cubic metre per second. The combination sewer line stretches along and below the level of Mölndalsån. When flow measurements were taken in 2014 it was determined that there is a great deal of infiltration leakage in this area. The stretch of sewer line along Nellickevägen was chosen for close examination because its proven that infiltration leakage was at its worst along this section of sewer. The current sewer lines were installed during the 1940s, after cctv examination it shows the concrete sewers to be partially deteriorated. The estimated leakage into the sewer line was around 120 litres per second.
During the project iMPREG and Avloppsrallarna installed 1,120 metres of DN 1500mm iMPREG fibreglass-reinforced liners that was cured with UV light. The wall thickness was 17.6mm to 18.5mm and it weighed approximately 15 tons per 100 metres. At the same time, 15 manholes were flushed and sealed by injection.
The project was carried out by Avloppsrallarna from April to mid-June. The project was implemented as a second competition based on the framework agreement called Flexibelt Foder [Flexible Lining].
‘We chose the no-dig solution because it meant limited interference in the area. The contractor only needed to dig up two manholes. Ten excavations were done in our project and at that point the contractor was already battling inward leakage from the nearby river.’
In order to have full flexibility during the implementation, it was also necessary that the uncured liner material could remain intact for at least a month before it was installed and cured.
‘Part of the sewer line went through Liseberg amusement park and it was important that the contractor was there as little as possible. It was also a requirement that the work was carried out when the park was closed, and no events or renovation were in progress.’
Four procurement processes
At the start of the project, part of the section of sewer line was selected for cleaning and film application during the autumn of 2015. The project planning and procurement processes took place from 2016 to 2018 and four procurement processes were required in order to implement the overall project. As a result, the project was postponed a year due to budget and re-prioritisation. The last procurement process concluded with the signing of a contract at the beginning of December 2018 by Avloppsrallarna.
‘The contractor planned and organised implementation in the beginning of 2019. The plugging of the sewer line and pump installation took place in the beginning of April with the final inspection was carried out on 17th June.’
The total contract amount was 13.9 million kronor (1,32 Mio. €).
West Link added
‘We ordered an additional 95-metre section during the period, which is part of the 1,120 metres. This took place in connection with the renovation of the sewer line before the West Link at Örgrytemotet for 1.7 million kronor (162 Tsd. €). The flushing and cleaning of the line was much more complicated than we anticipated and it was merely an item listed in the tender. There was also considerably more inward leakage in the line and manholes than we had measured and estimated in 2015.’
The project total to date is 16.7 million kronor (1,59 Mio. €), but that figure is likely to rise nearer the end of the project.
Antje Koppen commented ‘It was a difficult and unique project for both us and a great deal was learnt during the procurement process and implementation of the project. We are very pleased with outcome and how the project was ultimately executed.’
‘The project required a great deal of coordination and good collaboration between our operations unit. Liseberg and the contractor considers it as a great success. The contractor also had to factor in a construction site for Peab’s new offices. The site was in operation during the project period and additional coordination was necessary to gain access to their work area. We tried to involve all parties at an early stage in the project planning in order to be able to execute the project as smoothly as possible.’
Test samples have been taken and sent to RISE for examination of three-point flexural bending, short time testing and residual styrene content.
‘We have not received all of the results yet, but the results for two sections have been approved.’