To keep any one spot from becoming too heavily contaminated?

You should not drink village well water as it is usually heavily contaminated with impurities.

Money recovered from police raids on the drugs trade are often heavily contaminated.

An August 2007 analysis found the water was heavily contaminated with faecal material.

The site was heavily contaminated and had to be cleaned up before use.

This area is still heavily contaminated and has no inhabitants.

Dealing with the more heavily contaminated water near the reactor building will be an even greater problem, officials said.

Soils at the site were also heavily contaminated prior to removal and treatment.

Because of that, the island remains heavily contaminated today.

Oil leak occurred and caused the both ports heavily contaminated.