The contamination field in the database is used to record an estimation of the possibility of modern contamination in a context. In KAP terminology, it does not refer to the possible mixing of ancient contexts during the process of excavation (which should be noted clearly in the context description). There are three options for marking estimates of contamination: unlikely, possible, and probable.
Once topsoil and evidence of modern intrusion(s) have been excavated and removed, most subsequent contexts should be marked as having unlikely contamination: they should be buried beneath strata, features, installations, or deposits that do not appear to have been disturbed; they should be closed within a few days of when they were opened; and they should bear little if any evidence of bioturbation.
Context should be marked as having possible or probable contamination when they have been exposed over the off-season or for a longer period, when there is evidence of bioturbation, and when they appear to be otherwise disturbed in some way by recent or present-day activities.
The contamination estimate is used by various specialists at Kaymakçı to help prioritize material analyses, so it is extremely important to make the estimates carefully and to remember that modern contamination is not the same thing as mixing between ancient contexts.