The work here presents results from the study of the monitored data collected during a 2-year period at the viaduct of Grande Ravine at the Reunion Island. Based on the records collected by a set of anemometers, pressure sensors and accelerometers, it was possible to establish a wind model for the Grande Ravine implantation site, to estimate force coefficients for the deck, and to identify modal properties (vibration frequencies, damping and modal configurations). From the analysis of the structural response, it was possible specifically to identify a case of very slight vortex induced vibration, which is described in detail in this paper.