Contracts let by the board of township supervisors without advertising for bids shall also be in writing specifying the work to be done, the time in which it is to be completed, and the amount to be paid, and the board may require the contractor to furnish a bond with approved sureties in such sum as it shall deem sufficient, conditioned for the faithful performance of the contract according to the plans and specifications.
SDCL 31-13-7