"Another barometer for the condition of the river is the condition of the life that lives on the bottom. Needless to say, in 1964 in pool 2 there wasn't much on the bottom with the exception of sludge worms. There is a worm that can live in sewage sludge, and that's about all that was present there in pool 2 at the lower end of the pool in the area where we found a lack of fish.
"But as the river recovered, one really wonderful thing that's happened is that the biota on the bottom has responded as well. The mayfly requires good water conditions and good bottom conditions. Now there are abundant hatches of mayflies in areas where they couldn't live in 1964. Some of the other pools of the river farther downstream in '64 the mayfly was even getting pretty scarce. If you go farther down the river towards Red Wing some of the work that I did about the same time show that the mayfly populations were low even down there. So there's been a wonderful recovery that has extended well up into pool 2 and up into the Twin Cities area."