In Myrsjön’s stormwater dam, nature’s own processes are used to purify the stormwater that comes from a nearby industrial area.
Myrsjön lake and its sediment used to contain high contents of heavy metals and oils as it is located close to an industrial area. In order to control pollution, the old storm water conduit has been replaced by an artificial wetland where the storm water winds its way through a winding ditch and a dam, before it enters into the lake.
The dam has several tasks:
– To equalize the water level between the steps so that the differences in flow do not become too large between, for example, “spring flood” and dry periods.
– Sedimentation: heavy particles sink to the bottom and bring with them various pollutants
– Removal of oil residues: the outlet from the trench is at the bottom, which means that the oil stays there and never reaches the polishing pond.
Stormwater Strategy in the Municipality
The Myrsjön lake is located in the municipality of Nacka, which has a comprehensive stormwater strategy. The strategy states, for example, that at an early stage the necessary areas for stormwater management should be reserved. Land and buildings must be laid at levels that allow stormwater to be diverted to the ground in extreme rain without damaging properties or other important social functions (elevation). The municipality must also set requirements that lead to builders, property owners and others handling their stormwater sustainably. Special stormwater investigations are carried out in the initial phase of almost all urban building projects.