With the current system, we sometimes have to release untreated wastewater into Lake Mälaren – known as overflow discharge – during periods of heavy rainfall that flood the drains. When we build the new wastewater tunnel between Bromma and Sickla, we will be reducing overflow discharges to Lake Mälaren by connecting the Årsta Tunnel overflow discharge tunnel and pumping stations.
The new treatment technology will reduce our nitrogen emissions into the Baltic Sea by 40 per cent. Membrane technology will also make it possible to remove microplastics, contaminants, particles and drugs from wastewater in the future Transportation of sewage sludge through residential areas in Bromma and Sickla will no longer be necessary when wastewater treatment has fully relocated to the mountain at Henriksdal.
The entire project will cost around SEK 9 billion.
To cover the cost of the investment, it will be necessary to increase water charges gradually from SEK 10 to SEK 12.50 per cubic metre.
But water charges in Stockholm will still be some of the lowest in Sweden even after the increase.
The Bromma plant was the first treatment plant in Stockholm and was opened back in 1934. A lot has happened since then – the area around the treatment plant has been filled with thousands of homes.
The treatment plant, which is above ground, requires a safe zone of 200 metres all around it, and it is located in a densely populated area with properties, roads and an underground railway line nearby, which limits expansion options.
Stockholm is growing quickly and more treatment capacity is needed, and so we need a different solution. The Henriksdal treatment plant can be expanded, and upgrading the treatment plant by means of new technology will allow capacity to be doubled, so it will be possible to close down the Bromma treatment plant.
It is rare for homes to be damaged during blasting operations. Even so, we carry out pre-inspections of the properties within the area expected to be impacted so as to ensure that our blasting operations do not cause damage to properties. And a post-inspection is carried out when our blasting work is complete. If you discover damage to your property after we have been blasting in your area, you can apply for compensation. An independent inspection company will then carry out an investigation into the damage in order to identify the causal link between the damage and the work done. You will be compensated in full for any damage deemed to be caused by our blasting operations.
Membrane technology is based on the principle of separating the sludge from the treated wastewater by filtering the water through a physical barrier – a membrane – with tiny pores. This allows smaller particles, microplastics and contaminants to be intercepted. The technology also paves the way for the option of removing drug residues.
Membrane technology also requires less space, which means we can relocate all treatment to the mountain at Henriksdal.
Greater water volumes can be treated, and the water released will be cleaner and surpass the world's most stringent emissions requirements by some margin.
The system is made up of modules, and in total 1008 membrane cartridges of this kind will be installed at the Henriksdal plant. Membrane technology is a tried and tested method that has been used successfully in a number of other major cities, but Henriksdal will be the first one on this scale.
We have also implemented a successful pilot project in order to test the technology.
The Sickla plant, part of the Henriksdal treatment plant, is blasted into the rock at Hammarbybacken. The existing plant will be extended and supplemented with another entirely new treatment plant. We will be blasting out around 530,000 cu m of solid rock in total – covering an area of around the same size as the Globe Arena – for a new plant that will accommodate primary treatment, grit chambers and chemical treatment with pre-sedimentation.
Our aim has been to build as short a tunnel as possible while impacting on people living along the tunnel route as little as possible. This is why the tunnel passes beneath the city's own land and under existing tunnels as far as possible. We also need to take geological conditions into account, because building tunnels in rock is better than building them in clay. Another prerequisite for the project is the fact that the tunnel has to pass the Eolshäll pumping station in Hägersten.
We will be starting to build the tunnel in 2020. The tunnel will be built from a number of directions simultaneously, working from the six establishment zones that will be constructed. The tunnel will be completed and ready to use by 2026.
There are all kinds of different tunnels underneath Stockholm – for vehicles, trains, electricity, gas, district heating, broadband, water and sewerage. There is an enormous amount of intelligence and experience available when it comes to building tunnels under Stockholm, and it is very rare for tunnel construction to result in damage or injuries.
We will be constructing establishment zones in six locations along the route of the tunnel, and we will be fencing these in when tunnel construction begins. These locations have been selected in order to impact on the environment as little as possible. We will be placing site huts, vehicles and materials required for the work in these zones. We are planning to construct the establishment zones in
Trucks carrying rock spoil will be travelling to and from the establishment zones. These trucks will have to follow specifically designated routes. The further away from the zone you are, the less disruptive noise you will hear. We will restore the area in consultation with the landowner when construction of the tunnel is complete.
Anyone living nearby will notice when we carry out blasting operations – you will hear structure-borne noise when we drill and the sound of the explosion itself. Disruption from blasting operations and drilling noises will peak when the tunnel front is nearest to homes. The noise will decline as work on the tunnel progresses.
Yes, heavy transport operations will be taking place in the areas where we are blasting as we will need to remove rock spoil from the areas. Our trucks will be based at the establishment zones and have to follow specifically designated routes. The number of transport movements will vary throughout the construction process.
We have permission to work between 7am and 10pm on weekdays. We will use that time so that work progresses more quickly. This will allow us to reduce the overall disruption to people living and working in the area. We will sometimes be carrying out blasting work late at night. This is because blasting fumes have to be allowed to escape after a blasting operation so that we can start working straight away next morning.
You may notice blasting fumes in the form of a "dust cloud" and odour that rapidly dissipate in the air – this is non-hazardous to health.
The basic rule is that anyone affected by noise above the Swedish Environmental Protection Agency's guideline value of 45 dBA during the day or 35 dBA during the evening for more than a week will be offered alternative accommodation. However, if you work at home, are retired or have a job that means you have to sleep during the daytime, for example, this can also be taken into account. If you feel that the disruption is so problematic that you cannot remain at home, you will be guaranteed alternative accommodation for the period of the excess noise.
It is rare for buildings to be damaged by blasting operations. To make sure your house will not be affected by the tunnel, an independent inspection company will carry out thorough inspections of buildings near our operations before, during and after our work. You will receive compensation in full if our work causes any damage to your property.
If you discover damage to your property after we have been blasting in your area, you can apply for compensation. An independent inspection company will then carry out an investigation into the damage in order to identify the causal link between the damage and the work done. You will be compensated in full for any damage deemed to be caused by our work.
To report any damage, please get in touch with us on 08 522 128 80 or send an email to firstname.lastname@example.org. We will record the matter and send a claims adjuster from an independent inspection company to visit you. A decision will then be posted to you. You will be compensated in full for any damage deemed to be caused by our work.
Yes, you can apply for compensation if anything you own is damaged as a result of our work; if something falls off the wall because of the vibration, for example. An independent inspection company will then carry out an investigation into the damage in order to identify the causal link between the damage and the work done. You will be compensated in full for any damage deemed to be caused by our work.
All buildings and facilities that may be affected by the project will be inspected by an independent inspection company both before and after work. We will inspect all buildings within a radius of 150 metres from the tunnel construction site, Henriksdalsberget and the Sickla plant. Information about inspection work will be posted to anyone affected well ahead of time before we start work. Inspections will be carried out as close to the start of construction as possible, approximately one month before construction work may start to affect the buildings.
If the tunnel is to be routed underneath your property, you will receive a one-off compensation payment from Stockholm Vatten och Avfall. Firstly, the value of the interference with your property will be assessed. You will then receive a proposal for a land leasing agreement that regulates how much compensation you will receive. The principles of compensation are regulated in the Expropriation Act, which states that the property owner must receive compensation for interference on the basis of an assessed reduction in market value, including a supplement of 25 per cent. We will also increase that amount by 20 per cent in the land leasing agreement that we offer.
If you decide not to conclude a land leasing agreement with us, the issue will be submitted to Lantmäteriet for a decision. You may also decide to sign the land leasing agreement without accepting the compensation we offer. In this case, we will agree on all the other terms of the agreement, and only the issue of compensation will be referred to Lantmäteriet.
Along the tunnel route there are properties with geothermal heating pumps that will be affected by the construction work. If you have a geothermal heating pump that is affected by the tunnel, we will contact you in order to investigate the extent to which your geothermal heating is affected and what compensation you should receive for this.