The commissioners of the main district on their own initiative may, or, if the commissioners are presented with a petition of the landowners meeting the essential requirements as to signers and contents of either Section 3--3 or Section 3--27 so far as the same may be applicable, they shall, examine the lands proposed to be included in the subdistrict and upon which any portion of the drainage system is proposed to be constructed and determine upon the system of local drainage which will best provide more minute or complete drainage or protection to such lands.
70 ILCS 605/7-2