Authority: IC 13-18-3-1; IC 13-18-4-1; IC 13-18-4-3; IC 13-18-4-4; IC 13-18-4-5; IC 13-18-17-5

Affected: IC 13-18-4; IC 13-18-17

Sec. 7. (a) Limited class ground water, classified according to section 4(c) of this rule, must meet the narrative criteria established in section 5 of this rule.

(b) Limited class ground water, classified according to section 4(d) of this rule, must meet the following requirements:

1. (1) A contaminant attributable to activities associated with coal mining, not including the disposal of coal combustion waste at a surface coal mine under IC 14-34, must meet the greater of the following:

   1. (A) The existing contaminant concentration.
   2. (B) The numeric criterion established in section 6(a) of this rule.
2. (2) A contaminant not attributable to activities associated with coal mining, including the disposal of coal combustion waste at a surface coal mine under IC 14-34, if the contaminant concentration exceeds the concentration attributable to a coal mining activity, must meet the numeric criterion established in section 6(a) or 6(d) of this rule.

(c) Limited class ground water, classified according to section 4(e) of this rule, must meet the following requirements:

1. (1) A contaminant attributable to pesticides, crop nutrients, or soil amendments that have been applied for agricultural purposes and used in a manner consistent with all applicable regulatory requirements shall meet the greater of the following:

   1. (A) The existing contaminant concentration.
   2. (B) The numeric criterion established in section 6(a) of this rule.
2. (2) A contaminant not attributable to pesticides, crop nutrients, or soil amendments that have been applied for agricultural purposes and used in a manner consistent with all applicable regulatory requirements must meet the numeric criterion established in section 6(a) or 6(d) of this rule.

(d) Limited class ground water, classified according to section 4(f) of this rule, must meet the following requirements:

1. (1) A contaminant with a drinking water class numeric criterion established in section 6(a) of this rule must have a numeric criterion of ten (10) times the drinking water class numeric criterion established in section 6(a) of this rule.

2. (2) If the commissioner determines that a numeric criterion for a contaminant without a drinking water class numeric criterion established in subsection 6(a) of this rule is necessary to protect human health, any natural resource, or the environment, a risk analysis shall be used to establish a numeric criterion for that contaminant and must:

   1. (A) receive approval from the commissioner; and
   2. (B) be based on appropriate toxicological data.

(e) The naturally occurring concentration of a contaminant in limited class ground water shall be the numeric criterion if that contaminant occurs at a concentration greater than the limited numeric criterion established in subsection (b), (c), or (d).

(f) If limited class ground water at a facility, practice, or activity is determined to have one (1) or more contaminant concentrations above the numeric criteria established in this section that are not attributable to the facility, practice, or activity under consideration, an agency shall manage the facility, practice, or activity or implement programs such that:

1. (1) the facility, practice, or activity causes no further increase in the concentration of the contaminant determined to be above the numeric criterion established in this section; and
2. (2) any design standard or management requirements that apply to the facility, practice, or activity are at least as stringent as the design standard and management requirements that would be applied to a facility, practice, or activity where ground water does not have one (1) or more contaminant concentrations above the numeric criteria established in this section.

(g) The commissioner may allow an appropriate site specific, risk based numeric criterion different from the numeric criterion established in this section to be applied to limited class ground water at and beyond the boundary of the ground water management zone established according to section 9 of this rule.

(Water Pollution Control Division; 327 IAC 2-11-7; filed Feb 4, 2002, 11:00 a.m.: 25 IR 1880; readopted filed Jun 4, 2008, 11:07 a.m.: 20080702-IR-327080207BFA; readopted filed Jul 30, 2014, 4:04 p.m.: 20140827-IR-327140189BFA; readopted filed May 27, 2020, 11:52 a.m.: 20200624-IR-327200186BFA; readopted filed Oct 18, 2024, 1:57 p.m.: 20241113-IR-327230810RFA)