187] FAUNA OF BIG VERMILION RIVER—BAKER 89 
pollutional, and (3) contaminated or contaminate; and to these we will 
add ‘clean-water’ to indicate the conditions and organisms substantially 
equivalent to those of the natural, uncontaminated stream.” 
Judging Salt Fork by these standards of impurity, we would say that 
from the Urbana sewage outlet to the first bridge below the Champaign 
sewer outlet, a distance of about two miles, the stream is in a septic condi- 
tion. From this point to about two miles below St. Joseph it is polluted. 
From this region to Homer Park, below the dam, it is contaminated. 
Below the dam there is probably some contamination at times, but the 
fauna is a clean water one and the stream would be classed as a clean water 
stream, being unmodified by sewage conditions. The lower part of Salt 
Fork near Middle Fork, and Middle Fork and the Big Vermilion as far as 
Danville are clean-water streams with a large and varied fauna of mussels, 
crayfish, and insect larvae. Below Danville there is sewage pollution, and 
conditions are again unfavorable. 
