In December 2014 the Environmental court’s verdict limited the maximum allowable groundwater leakage into the permanent installations of E4 The Stockholm bypass.
A maximum of 3 800 000 liters of groundwater per day is allowed during 9 of 12 monthly averages per year. In the other 3 monthly averages the leakage can exceed this (no upper limit seems to be given in the verdict).
The water that infiltrates the tunnel system will be contaminated and pumped to a water treatment plant. The plant is still in the drafting stage and the Swedish Transport Administration does not know how well it can purify the water. If it is considered clean enough it will be pumped into lake Mälaren. If the water can not be cleaned to drinking quality it will be pumped out into the Baltic sea.
A protective barrier against water seepage will be in place where the tunnels pass under housing areas. Due to the cost our nature reserves will not get the same strong protection.
The Stockholm bypass tunnels under the island of Lovö. Lovö has been populated since the bronze age and today hosts a living farmland in a historical landscape. Swedish Transport Administration writes in the EIA about compensation for crop loss and how to handle wells running dry. In prestudies to the EIA they calculated the amount of water different farm animal drinks per day. The plan, if needed, is to bring in water by tankers for as long as the road is in use.
While many people may think groundwater is replenished by rain and melting snow the way lakes and rivers are, new Canadian research shows that underground water is actually renewed much more slowly.
Half of the Stockholm bypass is constructed within “East Mälaren Water Protection Area”.
Lake Mälaren is the freshwater supply for the Stockholm metropolitan area, about
2 million people. Our three water treatment works are all in danger from spills because of the intense traffic of barges and ferries during the 10 years of construction. When the expressway is operational the ventilation towers will spew out unfiltered exhaust full of PM10 particles and nitrogen over the drinking and fishing water.
The Swedish Transport Administration and the City of Stockholm already knows that the stormwater basin they are planning at Vinsta junction will neither hold nor clean all its water. The nitrogen rich wastewater will be siphoned off to a small recently restored lake that has its outlet into Lake Mälaren.
In the Sätra and Igelbäcken nature reserves creeks may run dry. The water from the project will not likely be clean enough so freshwater (tapwater) has to be pumped in, for as long as the road is in use.