The background

In recent years, many urban sewerage systems have been undersized, which means that the water has not always been able to drain away quickly enough, eventually resulting in flooding. 

In 2020, Lars Knudsen and Christian Rosenvinge, both with 35 years of experience in rainwater management, therefore decided to establish the company, URBAN WATER RETENTION (UWR). In collaboration with The Municipality of Frederiksberg, UWR initiated a project where the goal was to find a sustainable solution to store and handle the increasing water volumes.

The process

“After the initial discussions with The Municipality of Frederiksberg, the next step was to find the right supplier of plastics and rubber,” says Lars Knudsen and continues: "We already had a dialogue with a supplier of plastics, but as fate would have it, we were introduced to AVK GUMMI by chance. As it turned out that AVK GUMMI had a sister company, AVK Plast, we quickly concluded that this synergy suited our project perfectly.”

Following a thorough review of the requirements for the rubber gasket, we determined which material was best suited for water and for withstanding the great physical stress that the plastic cassettes are exposed to.

"It was clear to us that UWR had an innovative and exciting project with lots of possibilities," says Peter Lorentzen, Managing Director at AVK GUMMI and adds: "The fact that the UWR system represents a consistent and responsible approach to climate and CO2 challenges with focus on sustainability is completely in line with our own values.”

”Throughout the entire process, we have always been met with a solution-oriented approach – not only from the management, headed by Peter Lorentzen, but also from Thomas Ulrich-Hansen, Senior Engineering Specialist at AVK GUMMI. With his many years of experience and immense knowledge within the field of rubber, Thomas has been an indispensable driving force for the project,” says Lars Knudsen.

The solution

“Together with The Municipality of Frederiksberg, we had a list of 40 items, of which we managed to solve 39," says Lars Knudsen. "The design means that we now have a system where the boxes are positioned as close to the pavement surface as possible, which means less stress, faster installation, fewer excavators and shortened construction time – with great importance for the parking facilities in the cities.”

The lifetime of the UWR system means that distribution companies and municipalities can achieve project cost savings compared to traditional basin solutions. Furthermore, the overall CO2 footprint is reduced.

The future

At UWR, there is no doubt that the collaboration with AVK will continue in the future. As soon as the first project is completed, the next tool will be launched.

”The potential is great, and the next step for us will be to market the product outside Denmark too. Therefore, we have decided to participate at the Ifat Munich 2024 on 13 – 17 May 2024 where we look forward to introducing the UWR system to the trade show visitors,” concludes Lars Knudsen.


Pipe system for handling rainwater


UWR is a team of experienced dedicated experts within water, geophysics, plastics, rubber, facilities and production who has developed an intelligent pipe system for more efficient rainwater management. With this innovative solution, the construction period and CO2 emissions as well as the total construction costs are reduced. The UWR System is patented and verified by a Danish approved technological service institute.

  • Near surface basins
  • A square pipe system designed as building blocks that can be connected and stacked. Maximum height is 2.46 m with 40 cm coverage. There is no limit to width and length
  • Pavement and foundation layer of 40 cm
  • CO2 accounting and traceability
  • Lifespan 75+ years
  • Significant savings in
  • construction costs and time
  • Attractive project economy
  • Produced in Denmark


Betty Nansens Alle

Boligforening Østerbro

Frederiksberg Kommune

The cooperation with the management and the technical team at AVK GUMMI has been the driving force behind the success of our project. Not for one single moment have we had any doubts as to the support and invaluable knowledge, which has helped us fulfil our goal and get this far.
Lars Knudsen, Partner at UWR