Application of flow and transport models to the polluted Honkala aquifer, Säkylä, Finland

High concentrations of tetrachloroethylene were discovered in groundwater samples taken from the Honkala aquifer in the municipality of Säkylä in southwestern Finland. The contamination was traced to a dry-cleaning laundry located close to a tributary esker which is connected to the Säkylänharju esker in the northeastern part of the area. The Weichselian and Holocene sediments of the area include till, sand and gravel and also glacial and postglacial clay deposits. The groundwater flows west towards Pyhäjärvi (a lake in the municipality of Säkylä). A study was launched to test the applicability of numerical groundwater models in developing an overview of groundwater flow and contaminant transport in the area and prediction of the timing of natural attenuation. Modelling was conducted with the MODFLOW, MODFLOWP and MT3D codes, the resulting simulations indicating a natural attenuation time of more than 30 years would be required for the aquifer. Active aquifer restoration would require pumping and treatment of the polluted groundwater.