California Code of Regulations
Title 23 - Waters
Division 3 - State Water Resources Control Board and Regional Water Quality Control Boards
Chapter 15 - Discharges of Hazardous Waste to Land
Article 5 - Water Quality Monitoring and Response Programs for Waste Management Units
Section 2550.4 - Concentration Limits

Universal Citation: 23 CA Code of Regs 2550.4

Current through Register 2024 Notice Reg. No. 38, September 20, 2024

[Note: The special applicability of this section is described in § 2550.0(a) of this article; see also § 2510(a) of this chapter.]

(a) For each constituent of concern specified pursuant to section 2550.3 of this article (or for a hazardous constituent that is addressed by a cleanup and abatement action taken pursuant to SWRCB Resolution No. 92-49 [section 2907, Title 23 of this code]), the discharger shall propose one of the following for each medium (including ground water, surface water, and the unsaturated zone) that is monitored pursuant to section 2550.7 of this article (or that is included in a cleanup and abatement action under SWRCB Resolution No. 92-49):

(1) a concentration limit not to exceed the background value of that constituent as determined pursuant to subsection 2550.7(e)(11)(A) of this article;

(2) that the waste discharge requirements include a statement that, at any given time, the concentration limit for that constituent will be equal to the background value of that constituent, as determined pursuant to subsection 2550.7(e)(11)(B) of this article; or

(3) a concentration limit greater than background established pursuant to this section for a corrective action program.

(b) The regional board shall review the proposed concentration limits and statements and shall approve, modify, or disapprove each proposed limit and each proposed statement. Upon final approval by the regional board, each concentration limit and each statement shall be specified in waste discharge requirements. The regional board shall approve more than one concentration limit for different monitoring points in the same medium only if:

(1) more than one background condition exists within a particular medium;

(2) the statistical method approved for a constituent uses intra-well comparisons procedures; or

(3) concentration limits greater than background have been established for a corrective action program at the monitoring points in the zone affected by a release from the waste management unit.

(c) For a corrective action program, the regional board shall establish a concentration limit for a constituent of concern that is greater than the background value of that constituent only if the regional board finds that it is technologically or economically infeasible to achieve the background value for that constituent and that the constituent will not pose a substantial present or potential hazard to human health or the environment as long as the concentration limit greater than background is not exceeded. In making this finding, the regional board shall consider the factors specified in subsection (d) of this section, the results of the engineering feasibility study submitted pursuant to subsection 2550.9(c) of this article, data submitted by the discharger pursuant to subsection 2550.9(d)(2) of this article to support the proposed concentration limit greater than background, public testimony on the proposal, and any additional data obtained during the evaluation monitoring program.

(d) In establishing a concentration limit greater than background for a constituent of concern, the regional board shall consider the following factors:

(1) potential adverse effects on ground water quality and beneficial uses, considering:

(A) the physical and chemical characteristics of the waste in the waste management unit;

(B) the hydrogeological characteristics of the facility and surrounding land;

(D) the proximity and withdrawal rates of ground water users;

(E) the current and potential future uses of ground water in the area;

(F) the existing quality of ground water, including other sources of contamination or pollution and their cumulative impact on the ground water quality;

(G) the potential for health risks caused by human exposure to waste constituents;

(H) the potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to waste constituents; and

(I) the persistence and permanence of the potential adverse effects; and

(2) potential adverse effects on surface water quality and beneficial uses, considering:

(A) the volume and physical and chemical characteristics of the waste in the waste management unit;

(B) the hydrogeological characteristics of the facility and surrounding land;

(D) the patterns of precipitation in the region;

(E) the proximity of the waste management unit to surface waters;

(F) the current and potential future uses of surface waters in the area;

(G) the existing quality of surface water including other sources of contamination or pollution and the cumulative impact on surface water quality;

(H) the potential for health risks caused by human exposure to waste constituents;

(I) the potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to waste constituents; and

(J) the persistence and permanence of the potential adverse effects.

(e) In no event shall a concentration limit greater than background established under this section for a constituent of concern exceed the lowest concentration that the discharger demonstrates and the regional board finds is technologically and economically achievable. No provision of this section shall be taken to allow a concentration limit greater than background, for a constituent of concern, to exceed the maximum concentration that would be allowed under other applicable statutes or regulations (e.g., Maximum Concentration Limits established under the federal Safe Drinking Water Act [P.L. 93-523, codified as chapter XII of the Public Health Service Act at 42 USC 300f, et. seq.; regulations establishing MCL's are located in 40 CFR Part 141, Subpart B], etc.).

(f) For ground water, in evaluating risk pursuant to subsection (d) of this section to any biological receptor, the risk shall be evaluated as if exposure would occur at the point of compliance.

(g) Proposals for concentration limits greater than background shall include a demonstration that the aggregate of hazardous constituents in the environment will not result in excessive exposure to a sensitive biological receptor. In the absence of scientifically valid data to the contrary, theoretical risks from chemicals associated with the release from the waste management unit shall be considered additive across all media of exposure, and shall be considered additive for all chemicals having similar toxicological effects or having carcinogenic effects.

(h) A concentration limit greater than background may only be applied during corrective action, or during detection monitoring following corrective action, at monitoring points at which statistically significant evidence of the release has been determined.

(i) When a detection monitoring program incorporating a concentration limit greater than background is reinstated after a corrective action program has been terminated, each concentration limit greater than background shall be re-evaluated during each review of waste discharge requirements or at least every five years. If the regional board, upon re-evaluation, determines that the concentration of a constituent of concern in ground water, surface water, or the unsaturated zone is lower than its associated concentration limit by a statistically significant amount, the concentration limit for that constituent shall be lowered to reflect current water quality.

1. New section filed 5-24-91; operative 7-1-91 (Register 91, No. 22).
2. New first paragraph and amendment of subsection (a) filed 6-18-97; operative 7-18-97 (Register 97, No. 25).

Note: Authority cited: Section 1058, Water Code. Reference: Sections 13172, 13263, and 13267, Water Code.

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