Bornsjön is a water conservation area and Stockholm Water and waste reservoir. Bornsjön is also of great significance for the entire Stockholm County as it is the only reserve water revenue of a reasonable size that can provide the county for a long period in the event that all or part of Lake Mälaren would become unfit for drinking water production. In order to ensure water quality in the lake and the supply of drinking water so that the lake can be used as water reservoir in the future, the problem of internal phosphorus loading needed to be addressed.
The main objective of the project was to secure Bornsjön as a reserve water area for the future by addressing the internal phosphorus load in the lake. The water treatment plant will be used every August-October for reducing the phosphorus in the lake with traditional cleaning processes. To use such a technique for cleaning a lake is world-class unique and will be an extremely interesting project to follow in the next 20-30 years.
The direct effect is that Bornsjöns ecological status is improved and that the lake will continue to be used as a reserve water supply and safe delivery of drinking water. Further effects are that Bornsjöverket will increase the maximum capacity and flexibility of Norsborgs waterworks. The temperature of outgoing drinking water at Norsborgs waterworks is sometimes close and sometimes just above the National Food Agency’s limit value of 20 degrees. A supplement of 1000 m3 / h from Bornsjön can reduce the temperature by barely a degree during the summer months. Alkalinity from Norsborgs waterworks is today below the recommended limit of 60 mg / l. The high alkalinity of Bornsjön would increase this, thus reducing corrosion on the pipeline. Another effect of the plant is that the recovered sludge from the cleaning process in Bornsjöverket will be used on fields in the area as fertilizer.
On the 7th of September 2017 Bornsjöverket was opened by politicians and the CEO of Stockholm water and waste. The project is end inspected and all the water tests are completed with very good results.
The project is very unique and is placed in an environment that placed extremely high demands on us as entrepreneurs. This has meant that it was very important with clear procedures and plans to prevent any negative environmental impacts in the project. An extensive risk list, project plan, waste and mass management plan and joint organizational plan was made early with the Client. The contract was a design build contract that was carried out in collaboration with both the Client and subcontractors. This has been important to make everyone move in the same direction. We have worked a lot with well-being and cohesion, which we believe has been a success factor for the CEEQUAL work.
We have placed high demands on our subcontractors and have replaced our machine suppliers not less than twice during the project because we did not feel safe in how they lived up to our environmental requirements. High demands also require careful follow-up which we worked hard with in the project. Weekly environmental and protection rounds and extensive personal introductions have been a cornerstone of our work.
The project has received some attention in the media and a number of articles have been published. Our Client has also twice been interviewed about the project on the radio. Monthly we have compiled a so-called progress report that clearly demonstrated the project progress in both image and text. This report has been highly appreciated and spread both internally within Skanska and at the customer. It has been important to engage the final user (those who are going to operate the plant) and through the progress report this has been possible throughout the construction period.
Early we set goals and structure for how to establish and operate the workplace. The project has achieved our internal eco labelling “Green Workplace” with the highest level “Gold”. In addition, we also work with a “green map” explaining how we moved on during the project in the areas of energy, materials, climate and water.
People and Communities
Close collaboration with the customer’s warden and network has contributed to good cooperation with the various associations and residents in the area. Since it is a rich nature and open-air area with many active people, it has been very important that the workplace and the finished plant melted well into nature and that it was not restricted to people’s ability to move around in the area. Several consultations and information meetings have been held during the project. This has been highly appreciated by the public.
During the production phase we have focused a lot on minimizing environmental disturbances. An example of this is that we used steered drilling instead of digging trenches, we have planned for “unloading pockets” to not stop traffic on delivery and we have monitored noise, dust, order and remedy. A challenge was the foundation of knocked piles at different levels. The production manager together with geotechnicians and designers worked out a method of joining piles in the air. This resulted in a shorter time for piling and avoided significant noise and vibration.
Land Use and Landscape
Very little temporary land use has been used in the project. The areas used temporarily have been carefully covered with geotextile and protective materials and then restored to their origin. The project has had the possibility of storing masses as we had several workplaces in the area with different time frames and material requirements. This has enabled us to reuse all the masses that did not contain too much clay. No soil contamination has been encountered or arisen during the project. The project applied and received grants early to try a portable method for testing contamination of masses and water. It was very interesting and instructive, a method that can provide major benefits for managing masses.
In the design of the project, great importance has also been given to handling stormwater and possible contamination from vehicles in the future. A gravel tank/storage and a “disaster well” to minimize the spread of any leakage have been built into the parking area in front of Bornsjöverket.
The Water Environment
Water issues have naturally been of the utmost importance for this project. Extreme focus has been placed on not affecting the aquatic environment during the construction period and in the future when Bornsjöverket is in operation. Precise water measurements have been made during the construction period, both to check turbidity and water quality in terms of drinking water production. Materials incorporated into the plant and especially those components that may come into contact with drinking water have undergone careful evaluation. Our principle has been that you can eat it, you can build it. In the shafts we designed grumbling ponds that caught cloudy particles before the water was led to the lake. Throughout the course of the work, we have put in the turbidity curtains, which efficiently collect particles and materials. In order to minimize the risk of spillage and leakage from tanks and parked vehicles, areas have been carefully secured with double protection (plastic sheets, gravel and geotextile) to easily collect polluted material if an accident would occur. Upon introduction, everyone has received a thorough review of how a possible environmental accident should be handled which we successfully tested during the project.
Ecology and Biodiversity
The Environmental Impact Assessment of the Project (EIA) has been a sacred script throughout the works. All routines, plans and preparations have been developed based on the EIA. A number of unusual bird and fish species lives in the area, which we took great care of during the course of the project. The work has been moved in time to avoid disturbing birds, techniques such as steered drilling have been used to minimize turbidity to not disturb playing pike and work boats used in the lake have been sprayed with before launching to remove any diseases.
We have had good contact with birdwatchers in the area and they also had an appreciated presentation of the birds around Bornsjön for the entire project. A happy news during the course of the project was that a sea eagles incubated an eagle near our jobs! This was the nicest receipt we could get that we showed consideration during this sensitive time.
The Historic Environment
An archaeological survey was conducted prior to construction start, and it was identified that the workplace could be designed without interfering with the cultural-historical remains in the area. During dive work, skilled and experienced personnel have been aware of whether remains such as bridges should be found near the beach edge, however this did not occur.
Physical Resources – Use and Management (Energy, Water, Materials, Waste)
During production we have managed to reach almost zero drinking water use, as the lake with its clean water could provide us with water for both the establishment and the workplace. This is unusual to succeed in projects with a large proportion of site casted concrete. The project has worked a lot with mass management, and since we had two workplaces, it has been possible to store masses to partly reuse and partly to water out – which also resulted in fewer transports for the masses that could not be reused. Establishment in Skanska environmental sheds has enabled energy savings, for example, through effective heating methods, seals between sheds and light relays. The project has only used “green electricity”. Climate calculations were made early and followed up at a later stage of the project. This gives us a good understanding of what big posts that are climate-influencing and how changes in design also affect our climate footprint.
Source sorting in fractions has been done at the workplace and almost zero percent has gone to landfill. Cut down trees we left as logs of wood for residents in the area, which became an appreciated gift for the winter.
Smart solutions such as changing the depth of the shaft to minimize sheet piling have also yielded results both environmentally and economically. As mentioned earlier, we have had high demands on what material we could build into the plant. For example, we did thorough investigation on form oils, injection hoses, injections products and sealants. Sometimes we managed to find approved alternatives and sometimes we simply needed to reconsider the performance and managed problems in new ways.
Thanks to the “unloading pocket” we managed to arrange early in the project, we have managed to minimize disturbances on traffic in the area. In cases where we needed to work in and around roads, we have primarily used steered drilling to avoid road breaking. Traffic arrangement plans have been carried out, monitored and successfully end inspected by authorities.
Our subcontractor managed to change a long-haul transport by lorry to be partly transported by boat and only the last bit of lorry, which meant a lower environmental impact.
What were the main challenges for the project and how were these overcome?
The big challenge has been to comply with the high demands of the many natural values and stakeholders in the area. It has also been a great challenge to work with drinking water and to research and submit proposals on products/materials that have to meet the high demands made by the client.
What were the drivers and perceived benefits for undertaking a CEEQUAL assessment on this project?
Economic benefits, a sense of pride to work towards a clear goal and then achieve it. Improved relationships with residents and associations. Brand Boost.
How did the use of CEEQUAL influence the outcomes of the project? What was done differently because of the CEEQUAL process?
The involvement of local communities and stakeholders was made to a greater extent than we did in previous projects.
What elements of this project highlight best practice and innovation?
Layout area for vehicles and leakage preparations. Involvement of stakeholders in the area. Design of building and workplace to minimize environmental impact. Interest and commitment to technical solutions that saved us time and resources as well as a high commitment to environmental issues throughout the project.
CEEQUAL insights and case studies
Browse the latest insights, thinking and case studies from CEEQUAL