The environmental manager at a West Coast refinery recently approached authorities at the local publicly owned treatment works (POTW) to determine what permit limits to expect if the refinery began discharging pretreated wastewater to the city sewer. Besides the usual limits on ammonia, oil and grease, and sulfide, the POTW staff presented the manager with a list of trace metals. The manager returned to the plant, uncertain of whether the discharge contained any of these metals, let alone whether their concentrations exceeded the limits. The manager’s counterparts at refineries in the Midwest and West have also found metals limits in their National Pollutant Discharge Elimination System (NPDES) permits. These managers were surprised to learn that their refinery wastewaters do contain some of these metals, albeit in trace concentrations. The metals enter the wastewater system at various points in the refinery. Methods are being developed to reduce their concentrations through pollution prevention, source control, and treatment.