In the summer of 1970, I was employed as a labourer by National Parks in Jasper. Late in the summer we began mixing the calcium chloride and fine gravel to be used on the roads in the winter. We broke bags of calcium chloride over the edge of the loader bucket each time the loader scooped a bucket from one pile to the other. The gravel pile was along the Athabasca just upstream of the airport. I didn't have a thermos but we had canvas waterbags that we filled and took with us every day. The bags slowly seeped water and cooled the water quite well despite the hot dry summer.
For some reason I forgot the waterbag one day and as the river water was clearer in August than at the peak of runoff in July, I went to the river and got a drink. The next day during a break I got quite a shock as I observed raw sewage floating down the river. All summer we had been working along fire roads in remote areas of the park and thought nothing of taking a drink from tiny streams or from the slope drainage pipes along the paved roads.
Thirty-eight years later, Jasper has a state of the art sewage treatment system, but the fish in the river are still exposed to all the myriad pharmaceuticals and their metabolites that the sewage system doesn't change.