As relates to this code and the ensuing regulations, a "Manual for Planning and Execution of State Permanent Improvements" may be published by the board or its designee for use by governmental bodies and included, by reference, in the regulations of the board. The manual may be revised as the board considers necessary, except that proposed changes are not effective until the board has provided the public at least sixty days to make written comments after notice of the proposed changes is published in South Carolina Business Opportunities.