When it appears upon the written petition of a number of freeholders in the drainage district equal to 50% of the number of freeholders whose lands are traversed by said drain from the point where said dam or dams are located to the upper terminus, that such improvement is desired to be made by damming such drain and maintaining and operating such dam or dams to control flow, water levels and seepage or to provide for pumping the drainage where necessary from said drain or watercourse, and that such improvement and the maintenance and operation of such dam or dams is necessary to properly drain said lands and to protect the lands through which said drain runs, or to protect the rights of freeholders above such dam or dams, or the rights of freeholders of land adjacent or contiguous to the drainage district, or for the purpose of irrigation, said petition stating where it is desired to construct said dam or dams and the proposed method of operation of such dam or dams to control flow, water levels or seepage, or how the drainage is to be removed and where it is to be emptied, the commissioner shall, as soon as practicable after receipt of such petition, proceed to examine said drain and pass upon the necessity of such improvement and whether such improvement is practicable and conducive to the public health, convenience or welfare, or an improvement or necessity to preserve the adjoining lands thereto, or to protect rights in lands, or for the purpose of irrigation.