In any county that has appointed a road commissioner pursuant to Section 2006 of the Streets and Highways Code, or in any county that has abolished the office of road commissioner and complied with Section 2006.1 of the Streets and Highways Code, the board may authorize the road commissioner, or a registered civil engineer under the direction of the county director of transportation, to have any work upon county highways done under his or her supervision and direction. The work may be done in any of the following ways:
(a)
By letting a contract covering both work and material. In that event, the contract shall be let to the lowest responsible bidder as provided in this article.
(b)
By purchasing the material and letting a contract for the performance of the work. In that event, the material shall be bought at the lowest possible cost and the contract let to the lowest responsible bidder as provided in this article.
(c)
By purchasing the material and having the work done by day labor, in which case advertising for bids is not required.
(d)
(1)By authorizing the county road commissioner or a registered civil engineer under the direction of the county director of transportation to execute changes or additions to the work for any contract pursuant to this section in an amount not to exceed five thousand dollars ($5,000) for contracts of fifty thousand dollars ($50,000) or less, or 10 percent for contracts over fifty thousand dollars ($50,000) but not to exceed two hundred
fifty thousand dollars ($250,000). In no event shall any change or addition to the work exceed a net total addition of twenty-five thousand dollars ($25,000).
(2)
For contracts whose original cost exceeds two hundred fifty thousand dollars ($250,000), the extra cost for any change or addition to the work so ordered shall not exceed twenty-five thousand dollars ($25,000), plus 5 percent of the amount of the original contract cost in excess of two hundred fifty thousand dollars ($250,000). In no event shall any change or alteration exceed two hundred ten thousand dollars ($210,000).
(e)
By purchasing the material and letting a contract for the work or by letting a contract covering both work and material without advertising for bids when the estimated cost of emergency work necessitated by the imminence or occurrence of a landslide, flood, storm damage, or other emergency exceeds
twenty-five thousand dollars ($25,000) and the public interest and necessity demand immediate action to safeguard life, health, or property.