Cross contamination occurs when any non-potable or hazardous liquid comes in contact with our fresh water supply.
Some examples include sewage or hazardous material dumped into a lake, pond or reservoir. This is an example of direct cross contamination; when the contaminant comes directly in contact with the fresh water.
The prevention of direct cross contamination is fairly obvious. As with the above example, we simply should not dump sewage or hazardous material into our fresh water. However, cross contamination occurs in many lesser known situations. Please see Backflow Prevention for more details.