In 1997, the California Governor signed into law Senate Bill 1320 (Sher), Chapter 295, statutes of 1997, which mandates that, before any CalEPA Board, Department, or Office adopts a final version of a rule-making, the scientific findings, conclusions, and assumptions on which the proposed rule are based must be submitted for independent external scientific peer review. This requirement is incorporated into the California Health and Safety Code Section 57004.
A copy of the California Statute can be downloaded here.
This law requires highly-qualified experts to perform impartial peer reviews to ensure that all proposed CalEPA rule-makings meet accepted standards of the relevant scientific disciplines and to prevent any influence on the rule-makings stemming from irrelevant findings, unwarranted claims, unacceptable interpretations, and personal views.
Update: In September of 2014, Governor Brown signed AB 1707, which amends Section 57004 of the Health & Safety Code. This amendment requires that the State Water Resource Control Board (the Water Board) and the 9 California regional Water Boards post on its website copies of the conducted reviews of proposed rulemakings.
A copy of this Amendment can be downloaded here.