Section 20400 - SWRCB -Concentration Limits. (C15: s2550.4) (California Code of Regulations)

§ 20400. SWRCB -Concentration Limits. (C15: s2550.4)

[Note: The special applicability of this section is described in s20380(a); see also s20080(a).]

(a) Proposal of Concentration Limits -For each Constituent of Concern (COC) specified pursuant to s20395 (or for a solid waste constituent that is addressed by a cleanup and abatement action taken pursuant to SWRCB Resolution No. 92-49), the discharger shall propose one of the following for each medium (under s20415, including ground water, surface water, and the unsaturated zone) monitored pursuant to s20415 of this article:

(1) Background Value -a concentration limit not to exceed the background value of that constituent as determined pursuant to s20415(e)(10)(A);

(2) Value Redetermined Each Time -that the WDRs include a statement that, at any given time, the concentration limit for that COC will be equal to the background value of that constituent, as determined pursuant to s20415(e)(10)(B); or

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

(b) Adoption of Concentration Limits -The RWQCB 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 RWQCB, each concentration limit and each statement shall be specified in WDRs. The RWQCB 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) CLGBs have been established for a corrective action program at the Monitoring Points in the zone affected by a release from the Unit.

(c) Establishing a CLGB -For a corrective action program, the RWQCB shall establish a CLGB [under ¶(a)(3)] only if the RWQCB 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 CLGB is not exceeded. In making this finding, the RWQCB shall consider the factors specified in ¶(d), the results of the engineering feasibility study submitted pursuant to s20425(c), data submitted by the discharger pursuant to s20425(d)(2) to support the proposed CLGB, public testimony on the proposal, and any additional data obtained during the evaluation monitoring program.

(d) Considerations -In establishing a CLGB for a constituent of concern, the RWQCB 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 Unit;

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

(C) the quantity of ground water and the direction of ground water flow;

(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 Unit;

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

(C) the quantity and quality of ground water and the direction of ground water flow;

(D) the patterns of precipitation in the region;

(E) the proximity of the 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) CLGB Ceiling -In no event shall a CLGB for a constituent of concern exceed the lowest concentration that the discharger demonstrates and the RWQCB finds is technologically and economically achievable. No provision of this section shall be taken to allow a CLGB 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 Subchapter XII of the Public Health Service Act at 42 USC 300 f, et. seq.; regulations establishing MCL's are located in 40 CFR Part 141, Subpart B), etc.].

(f) Receptor Location -For ground water, in evaluating risk pursuant to ¶(d) to any biological receptor, the risk shall be evaluated as if exposure would occur at the Point of Compliance.

(g) Additivity -Proposals for CLGBs 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 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) Applicability -A CLGB may only be applied during corrective action, or during detection monitoring following corrective action, at Monitoring Points at which "measurably significant" (see s20164) evidence of the release has been determined.

(i) Decreasing the CLGB -When a detection monitoring program incorporating a CLGB is reinstated after a corrective action program has been terminated, each CLGB shall be re-evaluated during each review of WDRs or at least every five years. If the RWQCB, 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 "measurably significant" (see s20164) amount, the concentration limit for that constituent shall be lowered to reflect current water quality.

(1. New section filed 6-18-97; operative 7-18-97 (Register 97, No. 25). 2. Change without regulatory effect amending subsections (a)(1), (a)(2) and (i) filed 5-19-2000 pursuant to section 100, title 1, California Code of Regulations (Register 2000, No. 20).)

Note: Authority cited: Section 1058, Water Code. Reference: Sections 13172, 13263 and 13267, Water Code; and Section 43103, Public Resources Code.

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