Transport Mitigation

This page last reviewed September 2, 2010


The California Clean Air Act (CCAA or Act) requires the Air Resources Board (ARB or Board) to assess the contribution of ozone and ozone precursors from upwind regions on ozone concentrations that violate the State ozone standard in downwind areas. The Act also directs ARB to establish mitigation requirements for upwind districts designed to mitigate their impact on downwind districts.

ARB originally established mitigation requirements in 1990 which are contained in Title 17, California Code of Regulations, Sections 70600 and 70601. These regulations were amended in 1993 and more recently in 2003. The Board adopted amendments on May 22, 2003, which were approved by the Office of Administrative Law on December 4, 2003, and became effective on January 3, 2004.

These amendments included in the 2003 staff report added two new requirements for upwind districts. These amendments require upwind districts to (1) consult with their downwind neighbors and adopt "all feasible measures" for ozone precursors and (2) amend their "no net increase" thresholds for permitting so that they are equivalent to those of their downwind neighbors no later than December 31, 2004. The amendments clarify that upwind districts are required to comply with the mitigation requirements, even if they attain the State ozone standard in their own district, unless the mitigation measures are not needed in the downwind district.

Prior to adopting amendments to the transport mitigation regulations in 2003, ARB staff conducted an extensive public consultation process which included two public workshops. Below, is information from public workshops that were part of the rule development process:

Workshops / Meetings

Currently, there are no workshops or other meetings scheduled.


Program Contacts

For more information, please contact Gayle Sweigert at (916) 322-6923.


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