[en] The Sewage Treatment Plant (STP) in Barueri, Sao Paulo, Brazil, processes a significant part of sewage generated in Sao Paulo city. Due to economic and technical problems, all the residual sludges produced in the STP in Barueri from 1988 to 1996 were cumulatively disposed over the land, in piles and in open areas, resulting in a quantity of about 215000 m³ of residues, deposited directly on the soil. The STP has two ponds, which were built to landscape the place. In the present work, instrumental neutron activation analysis (INAA) was used to determine metals (Ba, Co, Cr, Cs, Fe, Hf, Mo, Rb, So, Ta, Zn), semi-metals (As, Sb, Se), actinides (U, Th) and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in bottom sediments from one of the ponds, in order to verify whether it was contaminated due to the wastes generated by the plant. The results obtained were compared to the concentration determined in a soil profile and in a sample of rock, in natura, representing the lithologies of the region, and showed a homogeneous distribution of the elements all along the pond and indicated that only As, Cr and Zn can have their origin associated with the residues disposed around the pond. (author)