35 Ill. Adm. Code 364.303
Population Factor
Section 364
Section 364.303 Population
Factor
a) Under this factor, populations are computed for each segment
and converted into an adjustment factor. The population of a segment is
defined by the 1980 U.S. census population of the segment except where
inter-segment transfers of sewage occur, in which case the estimated population
whose sewage is tributary to the segment is added to the resident population of
the segment. Population figures of the incorporated and unincorporated
communities are recorded for each segment. Where a segment boundary splits a
township, the unincorporated population within the segment is prorated by
applying a percentage of the township population equal to the ratio of the
segment area in the township to the total township area. The populations of
the various political subdivisions within each segment are totaled.
b) The following population factors are applied as multipliers to
the water quality index values:
Segment
Population
Population
Factor
0
-
20,000
1.00
20,001
-
50,000
1.05
50,001
-
100,000
1.10
OVER 100,000
1.20