The material studied in this work was flooded in the city of S??o Luiz do Paraitinga, SP, Brazil on January 2010 during a record flood suffered by the river that pass through the region. The documentary collection belonging to the City Hall underwent emergency drying and recovery treatments including irradiation with gamma rays to the destruction of various cellulosic fungi. Seven record books with many pages in blank and presenting severe fungal and mold infestation were provided by the Public Archive of the State of S??o Paulo, in charge of the damaged official documents, as samples for the present investigation on the effects of gamma radiation in the recovery and preservation of paper supported collections that are victims of biological contamination. This study represents a very rare possibility of working with a real object of actual use, which suffered a real disaster, and not with material prepared in laboratory and subjected to a forged flood situation.