Twisted logic: You used chemical A. Chemical A is found in the groundwater; therefore, you are responsible for the contaminated groundwater.
Correlation does not equal causation. Those involved in science and statistics are familiar with this phrase. Correlation between two variables does not automatically imply that one causes the other. Correlation might provide us a clue, but all of the variables must be examined.
Examining all the potential causal factors is work, but it is where truth is found.