Notwithstanding Section 12751, the board of a district which has owned and operated water distribution or sewage disposal systems for at least eight years and has a population of 250,000 or more may authorize the general manager to act for the board in determining the lowest responsible bidder and awarding a contract to that bidder where the expenditure required by the bid price is less than one hundred thousand dollars ($100,000). When acting pursuant to this section, the general manager shall, in each instance, promptly notify the board of the action

taken.