The director shall designate marketing areas which he deems necessary or advisable to effectuate the purposes of this chapter, and in which he finds the conditions affecting the production, handling, and sale of market milk, are reasonably uniform.

The director may establish additional areas, or modify areas previously established, if he deems the establishment or modification of such areas necessary or advisble to effectuate the purposes of this chapter.

If the director finds, after a public hearing in and for each particular marketing area under consideration for consolidation, that conditions of production and handling are reasonably uniform in two or more such marketing areas in which stabilization and marketing plans are in effect, he may consolidate the areas.