When the district board shall find the proposed project or projects to be necessary for the proper operation of the district and economically feasible and such finding is recorded in its minutes, the bonds therefor shall be authorized by resolution of the district board. The bonds may be issued in one (1) or more series, may bear such date or dates, may be in such denomination or denominations, may mature at such time or times, not exceeding forty (40) years from the respective dates thereof, may mature in such amount or amounts, may bear interest at such rate or rates to be determined by the district board, may be in such form, may carry such registration and such conversion privileges, may be executed in such manner, may be payable in such medium of payment, at such place or places, may be subject to such terms of redemption, with or without premium, as such resolution or other resolutions may provide. The bonds may be sold at a public or private sale at, above, or below par, as shall be determined by the district board, plus accrued interest, in a manner to be provided by the district board. The bonds shall be fully negotiable within the meaning and for all purposes of the uniform commercial code.