By the end of 2005, Valero Paulsboro Refinery partnered with Rowan University to find pollution prevention (P2) opportunities. Water characterization was the first step taken to evaluate current environmental performance of the plant and possible P2 improvements. In addition, the characterization aims to develop a water reuse/regeneration scheme. In this paper, the methodology to achieve the above goals and the major findings are presented. The units considered in this work are two crude units (desalter and distillation columns of crude oil), two benzene recovery units (BRU), one sour water stripper, and a system of several cooling towers. A detailed water balance of the current use was created in this work; 94% of the streams were accounted. The major water-consuming and wastewater-producing units were located.