Which of the following is not considered an acceptable cleaning method for cargo-contaminated walls?

Leaving cargo-contaminated walls as is is not an acceptable cleaning method because it fails to address the potential risks associated with residual contaminants. Cargo contamination can lead to several issues, including the risk of damage to future cargo, the possibility of cross-contamination, and even health hazards if the contaminants are hazardous substances. By not cleaning the walls, these risks remain unmitigated, which can affect the integrity of the shipping container and the safety of subsequent loads.

In contrast, the other methods mentioned—hot high-pressure washing, power grinding/painting, and scraping—are all active cleaning techniques that can help remove contaminants from the walls. Each of these methods is aimed at ensuring that the container meets cleanliness standards necessary for safe use. For instance, hot high-pressure washing can effectively remove stubborn residues, while scraping can help dislodge particulate contaminants. Power grinding/painting not only removes contaminants but can also help in restoring the surface of the container, ensuring it is clean and ready for future use.

Thus, leaving the walls dirty does not meet the required maintenance practices for cargo containers and compromises safety and efficiency in shipping operations.