The person to whom the contract may be awarded shall execute a bond in the penal sum of not less than twenty percent of the contract price, with surety to be approved by the board of directors, payable to the drainage district and conditioned upon the faithful performance of the contract. All work shall be done under the direction and to the satisfaction of the engineer employed by the drainage district and subject to approval by the board of directors.
C.R.S. § 37-31-154