After the organization of any drainage district, the commissioners of such drainage district shall proceed as soon as they may deem expedient in the construction of said improvements; and in carrying on said construction or any extensions thereof they shall have the power to employ such assistance as they may deem necessary and purchase all materials that may be necessary in the construction and carrying on of the work of said improvements, and shall have power to let the whole or any portion of said work to any responsible contractor; and shall in such case enter into all agreements with such contractor that may be necessary in the premises.
Idaho Code § 42-2940