The TSCA regulations state that "No provision specifying a PCB concentration may be avoided as a result of any dilution." Thus, if you mix waste containing >50 ppm PCB with non PCB waste, the resulting mixture must be treated as PCB waste (>50 ppm), regardless of the final PCB concentration of the mixture.

The TSCA regulations set slightly more stringent standards for PCBs >500 ppm. Thus PCB wastes with 50-500 ppm PCBs should not be mixed with waste >500 ppm PCBs since the mixture must be handled as >500 ppm PCBs (regardless of the final concentration).