§ 66264.94. Concentration Limits.

(a) For each constituent of concern specified pursuant to section 66264.93, the owner or operator shall propose one of the following for each medium (groundwater, surface water and the unsaturated zone) monitored pursuant to section 66264.97:

(1) a concentration limit not to exceed the background value of that constituent as determined under section 66264.97(e)(11)(A);

(2) that the permit 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 section 66264.97(e)(11)(B); or

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

(b) The Department 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 Department, each concentration limit and each statement shall be specified in the facility permit. The Department shall only approve different concentration limits for different monitoring points in the same medium where necessary:

(1) to describe background conditions in multiple surface water bodies, multiple aquifers or geochemically dissimilar zones in the same aquifer;

(2) because the statistical method approved for a constituent uses intrawell comparisons procedures; or

(3) because 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 regulated unit.

(c) For a corrective action program, the Department shall establish a concentration limit for a constituent of concern that is greater than the background value of that constituent only if the owner or operator demonstrates and the Department 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 Department shall consider the factors specified in subsection (d) of this section, the results of the engineering feasibility study submitted pursuant to section 66264.99(c), data submitted by the owner or operator pursuant to section 66264.99(d)(2) 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 Department shall consider the following factors:

(1) potential adverse effects on groundwater quality, considering:

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

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

(C) the quantity of groundwater and the direction of groundwater flow;

(D) the proximity and withdrawal rates of groundwater users;

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

(F) the existing quality of groundwater, including other sources of contamination and their cumulative impact on the groundwater 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, considering:

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

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

(C) the quantity and quality of groundwater, and the direction of groundwater flow;

(D) the patterns of precipitation in the region;

(E) the proximity of the regulated 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 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.

(3) In making any determination under subsection (d) of this section about the use of groundwater in the area around the facility the Department shall consider any identification of underground sources of drinking water made under 40 CFR chapter 1 section 144.7.

(4) For groundwater, 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.

(e) In no event shall a concentration limit greater than background established under this section for a constituent of concern exceed any of the following:

(1) other applicable statutes or regulations (e.g., a maximum contaminant level (MCL) for that constituent promulgated under section 141.2 of the Safe Drinking Water Act (40 CFR Part 141 Subpart B) [P.L. 93-523, codified as Subchapter XII of the Public Health Service Act at 42 U.S.C. 300f; regulations establishing MCLs are located in 40 CFR Part 141, Subpart B]);

(2) the lowest concentration that the owner or operator demonstrates and the Department finds is technologically and economically achievable.

(f) 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 regulated 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.

(g) 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.

(h) When an owner or operator is conducting a detection monitoring program after a corrective action program has been terminated, each concentration limit greater than background shall be re-evaluated during each permit review. If the Department, upon re-evaluation, determines that the concentration of a constituent of concern in groundwater, 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.

HISTORY

1. New section filed 5-24-91; effective 7-1-91 (Register 91, No. 22).

2. Amendment of subsection (b)(1) and Note filed 4-12-2011; operative 5-12-2011 (Register 2011, No. 15).

Note

Note: Authority cited: Sections 25150, 25159 and 58012, Health and Safety Code. Reference: Sections 25150, 25159 and 25159.5, Health and Safety Code; and 40 CFR Section 264.94.