A simple model is proposed for evaluating the dilution and other main characteristics of a dense boundaryattached 3-D plume, created by the disposal of heavier effluent into a quiescent homogeneous ambient. It is based on matching requirements between the near-and intermediate field, which allow the calculation of necessary quantities at the initiation of the bottom plume in terms of the initial discharge parameters. The subsequent spreading is described through a generalization of available data.