Cal. Revenue and Taxation Code § 434

On or before September 1, 1976, the board, after consultation with the Timber Advisory Committee, shall prepare instructions setting forth temporary criteria and procedures for grading timberland on the basis of its site quality and operability. Five general site quality classes shall be established. These classes shall be the same as those adopted by the State Board of Forestry and Fire Protection pursuant to subdivision (d) of Section 4528 of, and Section 4551 of, the Public Resources Code. Within each of the five site quality classes, appropriate classes of operability shall be established, based on factors, such as accessibility, topography, and legislative or administrative restraints. On or before December 31, 1979, these classes shall be designated as operative or inoperative. Commencing with January 1, 1980, the board shall determine appropriate designations of operability. On or before March 1, 1977, each assessor shall grade all timberland within the county on the basis of these instructions. The assessor’s grading is subject to the appeals procedure established by law for other assessments, as provided in Chapter 4 (commencing with Section 721) of Part 2 and Chapter 1 (commencing with Section 1601) of Part 3.