(a) The commission will specify in the compliance plan the hazardous constituents to which the groundwater protection standard of §335.158 of this title (relating to Groundwater Protection Standard) applies. Hazardous constituents are constituents identified in Appendix VIII of 40 Code of Federal Regulations Part 261 that have been detected in groundwater in the uppermost aquifer underlying a regulated unit and that are reasonably expected to be in or derived from waste contained in a regulated unit, unless the commission has excluded them under subsection (b) of this section.
(b) The commission will exclude an Appendix VIII constituent from the list of hazardous constituents specified in the compliance plan if it finds that the constituent is not capable of posing a substantial present or potential hazard to human health or the environment. In deciding whether to grant an exemption, the commission will consider the following:
  (1) potentially adverse effects on groundwater quality, considering:
    (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 follows;
    (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 on 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 §335.159 adopted to be effective May 28, 1986, 11 TexReg 2347; amended to be effective May 20, 1999, 24 TexReg 3726