Authority: IC 13-14-8-7; IC 13-15-2-1; IC 13-19-3-1

Affected: IC 13-30-2; IC 36-9-30

Sec. 11. (a) For each constituent listed in Table 2 in section 16 of this rule and for every secondary constituent, as identified in subsection (c), the ground water protection standard must be considered to be:

1. (1) the maximum contaminant level (MCL) for that constituent, if a maximum contaminant level has been established;
2. (2) the secondary maximum contaminant level for that constituent, if a secondary maximum contaminant level has been established; or

3. (3) the background ground water quality established for that constituent, based on background ground water monitoring data approved by the commissioner, if:

   1. (A) a maximum contaminant level or a secondary maximum contaminant level has not been established; or
   2. (B) for a given constituent, the background ground water quality is higher than the maximum contaminant level identified in subdivision (1), the secondary maximum contaminant level identified in subdivision (2), or the health-based levels identified in subsection (b).

(b) The commissioner may establish an alternative ground water protection standard for constituents for which an MCL has not been established in accordance with the following:

1. (1) The alternative ground water protection standards must be appropriate public health and environmental protection based concentrations that satisfy the following criteria:

   1. (A) The ground water protection standard is derived in a manner consistent with the federal United States Environmental Protection Agency guidelines for assessing risks of environmental pollutants in accordance with the following Federal Register notices published on September 24, 1986:

      1. (i) 51 FR 33992*.
      2. (ii) 51 FR 34006*.
      3. (iii) 51 FR 34014*.
      4. (iv) 51 FR 34028*.
   2. (B) The ground water protection standard is based on scientifically valid studies, conducted in accordance with the Toxic Substances Control Act (TSCA) Good Laboratory Practice Standards as defined in 40 CFR 792*.
   3. (C) For carcinogens, the ground water protection standard represents a concentration associated with an excess lifetime cancer risk level within the 1 × 10-5 to 1 × 10-6 range.
   4. (D) For systemic toxicants, the ground water protection standards represent a concentration to which the human population could be exposed on a daily basis that is likely to be without appreciable risk of deleterious effects during a lifetime.

2. (2) The commissioner may consider the following in establishing ground water protection standards:

   1. (A) Multiple contaminants in the ground water.
   2. (B) Exposure threats to sensitive environmental receptors.
   3. (C) Other site-specific exposure or potential exposure to ground water.

(c) For the purposes of this rule, secondary constituents are identified as the following:

1. (1) Ammonia.
2. (2) Chloride.
3. (3) Iron.
4. (4) Manganese.
5. (5) Sodium.
6. (6) Sulfate.

*These documents are incorporated by reference. Copies may be obtained from the Government Publishing Office, www.gpo.gov, or are available for review at the Indiana Department of Environmental Management, Office of Legal Counsel, Indiana Government Center North, 100 North Senate Avenue, Thirteenth Floor, Indianapolis, Indiana 46204.

(Solid Waste Management Division; 329 IAC 10-21-11; filed Mar 14, 1996, 5:00 p.m.: 19 IR 1873; filed Aug 2, 1999, 11:50 a.m.: 22 IR 3854; filed Apr 24, 2020, 4:48 p.m.: 20200506-IR-329190411FRA, eff Apr 24, 2020, see Executive Order 20-15, posted at 20200422-IR-GOV200234EOA; readopted filed Oct 16, 2024, 11:58 a.m.: 20241113-IR-329230812RFA)