264.94—Concentration limits.
(a)
The Regional Administrator will specify in the facility permit concentration limits in the ground water for hazardous constituents established under § 264.93. The concentration of a hazardous constituent:
(1)
Must not exceed the background level of that constituent in the ground water at the time that limit is specified in the permit; or
(2)
For any of the constituents listed in Table 1, must not exceed the respective value given in that table if the background level of the constituent is below the value given in Table 1; or
| Constituent | Maximum concentration 1 |
|---|---|
| Arsenic | 0.05 |
| Barium | 1.0 |
| Cadmium | 0.01 |
| Chromium | 0.05 |
| Lead | 0.05 |
| Mercury | 0.002 |
| Selenium | 0.01 |
| Silver | 0.05 |
| Endrin (1,2,3,4,10,10-hexachloro-1,7-epoxy 1,4,4a,5,6,7,8,9a-octahydro-1, 4-endo, endo-5,8-dimethano naphthalene) | 0.0002 |
| Lindane (1,2,3,4,5,6-hexachlorocyclohexane, gamma isomer) | 0.004 |
| Methoxychlor (1,1,1-Trichloro-2,2-bis (p-methoxyphenylethane) | 0.1 |
| Toxaphene (C10H10Cl6, Technical chlorinated camphene, 67-69 percent chlorine) | 0.005 |
| 2,4-D (2,4-Dichlorophenoxyacetic acid) | 0.1 |
| 2,4,5-TP Silvex (2,4,5-Trichlorophenoxypropionic acid) | 0.01 |
| 1 Milligrams per liter. | |
(3)
Must not exceed an alternate limit established by the Regional Administrator under paragraph (b) of this section.
(b)
The Regional Administrator will establish an alternate concentration limit for a hazardous constituent if he finds that the constituent will not pose a substantial present or potential hazard to human health or the environment as long as the alternate concentration limit is not exceeded. In establishing alternate concentration limits, the Regional Administrator will consider the following factors:
(i)
The physical and chemical characteristics of the waste in the regulated unit, including its potential for migration;
(vi)
The existing quality of ground water, including other sources of contamination and their cumulative impact on the ground-water quality;
(viii)
The potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to waste constituents;
(vi)
The current and future uses of surface waters in the area and any water quality standards established for those surface waters;
(vii)
The existing quality of surface water, including other sources of contamination and the cumulative impact on surface water quality;
(ix)
The potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to waste constituents; and
(c)
In making any determination under paragraph (b) of this section about the use of ground water in the area around the facility the Regional Administrator will consider any identification of underground sources of drinking water and exempted aquifers made under § 144.8 of this chapter.