California’s tough rules for cleaning up contaminated property just got tougher.

In October, the Legislature amended the state’s Superfund Act to require health and environmental risk assessments of contaminated property slated for redevelopment. Assembly Bill 422 (AB 422) states that risk assessments must now analyze the impact of possible soil vapor intrusion into existing or proposed structures at the redeveloped site. In addition, AB 422 requires that the cleanup standards promulgated under the Porter-Cologne Water Quality Control Act be consistent with, and no less stringent than, those required under the California Superfund Act. The law seeks to harmonize the rules of the State Water Resources Control Board and Regional Water Quality Control Boards with the standards enforced by the Department of Toxic Substances Control.


AB 422 will affect brownfields redevelopers, many of whom operate at the margins of economic feasibility. Although this legislation may end jurisdictional issues regarding which agency’s standards apply to a brownfields site, the new law adds additional expenses and complexity to the assessment process.


Vapor intrusion has emerged as a health and safety issue due to recent studies showing that toxic chemicals can leach into indoor air. Vapor intrusion occurs when volatile organic compounds (VOCs) found at some brownfields sites, and at former toxic sites, leach into indoor air and threaten human health. The new law requires that risk assessments prepared as part of a Superfund cleanup include best estimates of exposure to VOCs that may enter nearby structures through vapor intrusion.

In addition, because the rule harmonizes cleanup standards, no longer will the source, type, and extent of contamination determine which agency has oversight of a particular site or whether the water code or hazardous waste law is applicable.


The new law provides that the methods by which health risks are calculated must now be consistently applied at all cleanups, regardless of whether the Water Resources Control Board or Department of Toxic Substances Control is overseeing the cleanup.

Risk assessments will be required to include the development of reasonable maximum estimates of exposure to VOCs that may enter structures that are on, or proposed for, a redevelopment site.


Assessments prepared in conjunction with a response action will be based upon Subpart E of the National Oil and Hazardous Substances Pollution Contingency Plan (40 C.F.R. 300.400 et seq.), federal EPA standards, and “the most current sound scientific methods, knowledge, and practices of public health and environmental professionals who are experienced practitioners in the fields of epidemiology, risk assessment, environmental contamination, ecological risk, fate and transport analysis, and toxicology.”


The new law applies to orders issued by a state or regional board on or after January 1, 2008. However, orders issued before January 1, 2008, could fall within the new rules if a state or regional board makes a specified determination requiring a site-specific assessment of human health or ecological risks at a brownfields site.