Final answer:
A soiled disposable underpad from a patient under contact precautions for C. diff should be disposed of in a biohazard waste container.
Step-by-step explanation:
A Patient Care Technician (PCT) dealing with a patient under contact precautions for Clostridium difficile (C. diff) infection must adhere to specific protocols when disposing of contaminated waste such as a soiled disposable underpad. Contaminated waste that includes blood and feces poses a biohazard risk and must be handled with extreme caution. The appropriate disposal method for heavily soiled underpads in this scenario is to place them in a container designated for biohazard waste. This is consistent with health and safety guidelines that aim to prevent the spread of infection and protect both healthcare workers and patients from exposure to potentially infectious materials. It is essential that the technician uses the correct protective clothing, as per the referenced prevention protocols, and follows facility policies for the handling and disposal of biohazardous materials.