The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between ¹³⁷Cs in discharge canal seawater and station discharged activity and correlation of ¹³⁷Cs, ⁶⁰Co, and ¹³¹I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of ¹³⁷Cs and ¹³¹I in seawater versus biota are discussed. A good correlation between ¹³⁷Cs in seawater and ¹³⁷Cs in liquid waste discharged was observed (R²=0.8, p < 0.001). Similarly, correlation
was good for Nerita and discharged concentration of ¹³⁷Cs, ¹³¹I and ⁶⁰Co (R² =0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean ¹³⁷Cs decreased from the pre-operational levels: 7.0e3.6 Bq kg^-1 in soil, 0.91-0.016 Bq L^-1 in milk and 0.28-0.036 Bq kg^-1 in vegetation. Similarly, the mean 90Sr in these matrixes decreased from 3.9 to 0.26 Bq kg^-1; 0.37-0.011 Bq L^-1 and 0.34-0.022 Bq kg^-1 respectively. Cesium-137 of about 700 microBq m^-3 was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.