Method and apparatus for equalizing the digital performance of multiple ADCs includes structure andor steps for coupling at least one global line between the ADC’s resistor ladders to allow current to flow therebetween to balance the reference voltages applied to the comparators of the ADCs. Contaminated surfaces may be classified as Class C, Class B, Class A, or high-level radioactive wastes prior to treatment. The second power source is at a second voltage. In yet another embodiment an access port assembly is included.