The potential chemical impact of a treated sewage discharged from the ?Gdansk-Wschod? Sewage Treatment Plant to the Gulf of Gdansk was studied. A physical and chemical investigation of the sediments sampled in the area of the planned collector outlet as well as results of an earlier research were the basis for the present paper. A spatial distribution of majority of the studied sediment components shows a distinctive zoning that is clearly due to them being supplied by the Vistula River (Wisla River). This is particular for the mercury, lead, zinc and chromium as well as organic carbon and phosphorus. A distribution of the redox potential shows too a distinctive relation to the Vistula River mouth. Starting a sewage discharge through a new collector located between the two river mouths of the Wisla Smiala and the Wisla Przekop can move westwards the presently observed zoning of increased concentrations of some chemicals. However, most probably such changes will be small and they will not cumulate themselves over time.