Sec. 1. This chapter applies to the area consisting of the following counties:
(1) A county having a population of more than four hundred thousand (400,000) and less than seven hundred thousand (700,000).
(2) A county having a population of more than one hundred seventy thousand (170,000) and less than one hundred seventy-four thousand (174,000).
(3) A county having a population of more than one hundred twelve thousand (112,000) and less than one hundred twenty thousand (120,000).