Establishing a Starting Point
Let's begin by analyzing the health of the fish populations in Clearwater Lake. Since trout are the most sensitive to pollutants, I believe their health metrics will provide the most obvious clues.
Quality of Trout Populations by Location in Clearwater Lake

Change in Trout Length Throughout the Year

Plotted against the calculated average length.

Change in Trout Weight Throughout the Year

Plotted against the calculated average weight.

Length and weight (both indicators of health) seem fairly consistent.
A few blips(possibly natural variation) but nothing difinitive aside from what seems to be a decrease in both weight and length for the western population.

Let's put a pin in this for now and take a look at the water quality!

Change in Nitrogen Throughout the Year

Nitrogen and Phosphorus spike a few times during the year, but when you look at the weight and length graphs trout, the most sensitive of the species found in Clearwater Lake, are doing fine. Although it is interesting to see that the pH does not reflect this increased nitrogen. I would have thought that there would be an increase in acidity (or a lower pH) due to nitrification. But this phenomenon pales in comparision to rhe real concern: the spikes in heavy metals in the West, which go way beyond the what is permitted. The wild west is 2/2 right now... Let's see how the trout population is doing in terms of count:
Well it seems trout populations remain fairly consistent in every region of the lake aside from the west and south sides.... Something is going on over there in the west, for sure... Next we take a look at the suspects!

Documented Activity of the Suspects

Well it looks like ChemTech Manufacturing's maintenance shutdowns are somehow related to the heavy metal counts in the west... but how close is ChemTech Manufacturing to the western portion of the lake?

ChemTech's distance to each shore

Well... if ChemTech Manufacturing, located closest to the western shore, is documented to have maintenance shutdowns, which correspond to the increase in heavy metals...in the western portion of the lake... which also has a declining trout population, a species especially sensitive to pollution... I don't think it's a strech to say that ChemTech Manufacturing is responsible for the declining trout population in the west portion of Cleatwater Lake.