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It is like finding a needle in a hay stack, Environmental Scientist Rafael Casanova told Action 4 News.
           
For months he and his team have been searching 8 miles of water—looking for something that they are not even sure is there.
           
Over the months they have been able to narrow down those 8 miles to 3 miles.
           
“We’re finding the highest contamination between the Arroyo Colorado and Valley View Road,” Casanova said. “So we’ve narrowed it down.”
           
But still, it is a lot of water to cover.
           
Since Monday crews have been up and down the canal at least eight times a day.
           
They are looking for PCB’s or Polychlorinated Biphenyls.
           
It is an environmental pollutant that causes cancer in fish and has other effects on children and adults. 

"The boat is carrying two coils in the back. One is a receiver and one's a transmitter. It transfers back to the receiver to tell us if there is any buried metallic objects that can contain chemicals."
           
So far they have not found anything. 
Reporter:
"What happens if you don't find anything?"
Rafael:
"We don't find the source the fish will continue to be contaminated. We need to find the source."
           
There are 209 types of PCB’s out there, Casanova said. While they are not testing for all of them—they will make sure all ground is covered to keep those living in the area safe.