[en] This Working Report presents the main results of Posiva Oy's environmental monitoring programme on Olkiluoto Island in 2006. This is the third annual report. The environmental monitoring system supervised by Posiva Oy produces input for biosphere modelling for long-term safety purposes as well as for monitoring the state of the environment during the construction (and later operation) of ONKALO underground characterization facility. Although some of the nuclear power production related monitoring studies by TVO (the power company) have been going on from the 1970s, the repository-related environmental monitoring of Olkiluoto Island has only recently been comprehensive. Consequently, the first Biosphere Description Report was written in 2006. This work further produced some analyses belonging to the environmental monitoring programme, namely the estimates of biomass in terrestrial vegetation (forests) and a preliminary estimate of the biomass in terrestrial fauna (moose). In the monitoring data, the ongoing construction work (OL3, ONKALO and related infrastructure) is seen for instance in raised noise levels and deposition of base cations and iron. The land-use continues to change, but where there is natural environment, it resembles other coastal locations. The nearby marine environment is affected by the cooling water from the nuclear power plant. (orig.)