California Code, Government Code - GOV § 15640

(a) The State Board of Equalization shall make surveys in each county and city and county to determine the adequacy of the procedures and practices employed by the county assessor in the valuation of property for the purposes of taxation and in the performance generally of the duties enjoined upon the county assessor.

(b) The surveys shall include a review of the practices of the assessor with respect to uniformity of treatment of all classes of property to ensure that all classes are treated equitably, and that no class receives a systematic overvaluation or undervaluation as compared to other classes of property in the county or city and county.

(c) The surveys may include a sampling of assessments from the local assessment rolls.  Any sampling conducted pursuant to subdivision (b) of Section 15643 shall be sufficient in size and dispersion to ensure an adequate representation therein of the several classes of property throughout the county.

(d) In addition, the board may periodically conduct statewide surveys limited in scope to specific topics, issues, or problems requiring immediate attention.

(e) The board's duly authorized representatives shall, for purposes of these surveys, have access to, and may make copies of, all records, public or otherwise, maintained in the office of any county assessor.

(f) The board shall develop procedures to carry out its duties under this section after consultation with the California Assessors' Association.  The board shall also provide a right to each county assessor to appeal to the board appraisals made within the county assessor's county where differences have not been resolved before completion of a field review and shall adopt procedures to implement the appeal process.