Toxic chemicals and other hazardous materials such as oil, grease, and metals can be severely damaging to aquatic plants and animals. Over time these pollutants collect on streets, parking lots and driveways. During rain storms these substances are washed away with other pollutants and become concentrated in the runoff. In the Iron River watershed, these substances typically enter the streams via storm drain outlets and road crossings.

There is a corridor along the Iron River which spans roughly from M-73 to the US-2 bridge in Iron River.  Throughout this corridor many prime locations where toxic accumulation would be expected are present.  Heavy machinery equipment dealers and manufacturers, auto dealerships and maintenance facilities, and shopping area parking lots and city streets are all potential sources of toxic pollution.