California Code, Government Code - GOV § 25350

No purchase of real property, including any water right or other interest therein, of which the purchase price is in excess of the dollar limit established by ordinance adopted pursuant to Section 25350.60, or, if no ordinance is adopted, in excess of fifty thousand dollars ($50,000), shall be made unless a notice of the intention of the board of supervisors or, if applicable, the county officer authorized to purchase real property pursuant to Section 25350.60, to make the purchase is published in the county pursuant to Section 6063.  If no newspaper is published in the county, the notice shall be posted at least three weeks prior to the time the board meets to consummate the purchase in at least three public places in each supervisorial district.  The notice shall contain a description of the property proposed to be purchased, the price, the vendor, and a statement of the time the board will meet to consummate the purchase.

Nothing contained in this section shall be deemed to preclude the settlement of an action in eminent domain or the acquisition of any real property or interest therein for the uses and purposes of county highways without compliance with this section.