California Public Resources Code 21166 – When an environmental impact report has been prepared for a project …
When an environmental impact report has been prepared for a project pursuant to this division, no subsequent or supplemental environmental impact report shall be required by the lead agency or by any responsible agency, unless one or more of the following events occurs:
(a) Substantial changes are proposed in the project which will require major revisions of the environmental impact report.
(b) Substantial changes occur with respect to the circumstances under which the project is being undertaken which will require major revisions in the environmental impact report.
(c) New information, which was not known and could not have been known at the time the environmental impact report was certified as complete, becomes available.
(Amended by Stats. 1977, Ch. 1200.)