2023 California Code › Water Code - WAT › DIVISION 7 - WATER QUALITY › CHAPTER 5 - Enforcement and Implementation › ARTICLE 1 - Administrative Enforcement and Remedies › Section 13304.2.

13304.2. (a) For purposes of this section, “brownfield site” means a real estate parcel or improvements located on the parcel, or both that parcel and the improvements, that is abandoned, idled, or underused, due to environmental contamination and that is proposed to be redeveloped.
(b) The state board or a regional board may require a person conducting cleanup, abatement, or other remedial action pursuant to Section 13304 for a brownfield site to assess the potential human health or ecological risks caused or created by the discharge, using human health and environmental screening levels or a site-specific assessment of risks.
(c) In conducting a site-specific assessment of human health or ecological risks, the discharger shall address all of the following factors to the extent relevant based on site-specific conditions:
(1) An evaluation of risks posed by acutely toxic hazardous substances.
(2) An evaluation of risks posed by carcinogenic or other hazardous substances that may cause chronic disease.
(3) Consideration of possible synergistic effects resulting from exposure to, or interaction with, two or more hazardous substances.
(4) Consideration of the effect of hazardous substances upon subgroups that comprise a meaningful portion of the general population, including, but not limited to, infants, children, pregnant women, or other subpopulations that are identifiable as being at greater risk than the general population of adverse health effects due to exposure to hazardous substances.
(5) Consideration of exposure level and body burden level that alter physiological function or structure in a manner that may significantly increase the risk of illness and of exposure to hazardous substances in all media, including, but not limited to, exposures in drinking water, food, ambient and indoor air, or soil.
(6) The development of reasonable maximum estimates of exposure for both current land use conditions and reasonably foreseeable future land uses at the site.
(7) The development of reasonable maximum estimates of exposure to volatile organic compounds that may enter structures that are on the site or that are proposed to be constructed on the site and that may cause exposure due to accumulation of these volatile organic compounds in the indoor air of those structures.
(d) The state board or a regional board may document its decision to require a site-specific assessment of human health or ecological risks in a letter issued to the discharger pursuant to Section 13267, through amendment of the cleanup and abatement order issued pursuant to Section 13304, or through other written means that the board deems appropriate.
(e) (1) Except as provided in paragraph (2), this section applies only to an order issued by the state board or a regional board issued pursuant to Section 13304 on or after January 1, 2008.
(2) The state board or a regional board may require a site-specific assessment of human health or ecological risks at a brownfield site that is subject to an order issued before January 1, 2008, only if the state board or a regional board makes a determination that site-specific circumstances demonstrate the need for that assessment. A site-specific assessment pursuant to this paragraph shall be done in accordance with the authority granted to the state board or a regional board pursuant to this division, as it read on December 31, 2007.
(Added by Stats. 2007, Ch. 597, Sec. 2. Effective January 1, 2008.)