(a) The commission will specify in the compliance plan concentration limits in the groundwater for hazardous constituents established under §335.159 of this title (relating to Hazardous Constituents). The concentration of a hazardous constituent:
  (1) must not exceed the background level of that constituent in the groundwater at the time that limit is specified in the plan;
  (2) for any of the constituents listed in Table 1 of subsection (b)(1) of this section, 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
  (3) must not exceed an alternate limit established by the commission under subsection (b) of this section.
(b) The commission will establish an alternate concentration limit for a hazardous constituent if it 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 commission will consider the following:
  (1) potentially adverse effects on groundwater quality, considering the maximum concentration of constituents for groundwater protection described in the following Table 1 and:
Attached Graphic     (A) the physical and chemical characteristics of the waste in the regulated unit, including its potential for migration;
    (B) the hydrogeological characteristics of the facility and surrounding land;
    (C) the quantity of groundwater and the direction of groundwater follow;
    (D) the proximity and withdrawal rates of groundwater users;
    (E) the current and 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;
    (I) the persistence and permanence of the potentially adverse effects; and
  (2) potentially adverse effects of hydraulically-connected surface-water quality, considering:
    (A) the volume and physical and chemical characteristics of the waste in the regulated unit;
    (B) the hydrogeological characteristics of the facility and surrounding land;
    (C) the quantity and quality of groundwater, and the direction of groundwater flow;
    (D) the patterns of rainfall in the region;
    (E) the proximity of the regulated unit to surface waters;
    (F) the current and future uses of surface waters in the area and any water quality standards established for those surface waters;
    (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 potentially adverse effects.
(c) In making any determination under subsection (b) of this section about the use of groundwater in the area around the facility, the commission will consider any identification of underground sources of drinking water and exempted aquifers made under §331.13 of this title (relating to Exempted Aquifer).

Source Note: The provisions of this §335.160 adopted to be effective May 28, 1986, 11 TexReg 2347.