The airport is located in the watershed of the Märsta River (Märstaån). Run-off occurs to two creeks, Kättstabäcken which runs west of the airport and Halmsjöbäcken which runs through the airport area. Stockholm Arlanda performs water testing in the airport’s surroundings on a continuous basis. Every five years, a study of the bottom-dwelling fauna and other small animals living in nearby waterways is also conducted. Quantity and species composition are a good indicator of water quality.
Based on this study of the bottom-dwelling fauna, ecological status can be assessed. Good ecological status means that the water may not demonstrate more than small divergences from what is regarded as natural conditions for the type of waterway in the area under study.
“Moderately good” status in 2008
A study in 1988 showed that Stockholm Arlanda had some of the most polluted waterways in Europe. Thanks to various improvements − water treatment, replacement of urea with potassium formiate and increasingly thorough collection of glycol − the 2003 study showed a clear improvement. The 2008 study indicated that the ecological status improved in every waterway. In 1988, the status was “poor”, and after the 2008 study, it was considered to be “moderately good”.
In another study carried out in 2008, the chemical PFOS was found to be present in the sediment of Lake Halmsjön and elsewhere. The substance has limited toxicity but is subject to bioaccumulation. Swedavia (formerly LFV) has taken the initiative to finance a five-year project, RE-PATH, which is being carried out by IVL Svenska Miljöinstitutet AB, to study and map the presence of PFAS (perifluoroalkyl sulfonate) in general and PFOS in particular as well as study suitable remedies.
Monitoring of groundwater
Four times a year, groundwater samples are taken at about 15 sampling points around the airport. In addition, samples are taken continuously at all water treatment units at the airport.
What samples should be taken, how often they should be taken and what should be analysed are regulated in the airport’s environmental inspection programme. The results of all samples are presented in special reports covering a time period or area, as well as in the airport’s annual environmental report.
Stockholm Arlanda also has plans to construct more water treatment units at the airport.