California Code, Public Contract Code - PCC § 21031

(a) In all work of improvement or repair of any of the works or property of the district and in the furnishing of materials or supplies therefor, when the expenditures required exceed twenty-five thousand dollars ($25,000), the work shall be done by contract, and shall be let to the lowest responsible bidder, after notice by publication in a newspaper of general circulation published in the district for at least two insertions in a weekly newspaper or at least 10 insertions in a daily newspaper;  the notices shall state the work contemplated or the materials or supplies required, or both.  The board of trustees may reject any bid presented and readvertise in their discretion.  The board may declare and determine that in its opinion the work in question can be performed more economically by day labor or the materials or supplies can be furnished at a lower price in the open market, and they may proceed to have the work done or the materials purchased without further observance of the foregoing provisions of this section.

(b) In case of an emergency, the board of trustees may declare a state of great public emergency and proceed to have all necessary work done and materials and supplies furnished without further observance of the foregoing provisions of this section.  If notice for bids to let contracts will not be given, the board shall comply with Chapter 2.5 (commencing with Section 22050).

(c) None of the foregoing provisions of this section apply to work done by contract with the United States, the State of California, or any political subdivision, or public agency thereof.  Any work of improvement or repair provided for in this article may be located, constructed and maintained in, along, or across any railroad, public road, or highway in the County of Sacramento, in a manner that ensures security for life and property.  The board of trustees shall restore or cause to be restored the road or highway to its former state as near as possible to preserve its usefulness.