Authority: IC 13-14-8; IC 13-15-1-2; IC 13-15-2-1; IC 13-18-3-1; IC 13-18-4-1

Affected: IC 13-11-2; IC 13-13-5-1; IC 13-18-2

Sec. 24. (a) The disinfection procedures described in this section must be performed with one (1) of the following approved forms of chlorine:

(1) Calcium hypochlorite.

(2) Sodium hypochlorite.

(b) Gravel installed in a new production well must be chlorinated by use of the following method:

(1) Silica gravel for gravel pack must be disinfected with calcium hypochlorite or sodium hypochlorite before installation in a well at a rate that will produce a liquid concentration of at least fifty (50) milligrams per liter (mg/l) as the gravel is installed.

(2) The gravel, disinfected according to subdivision (1), must be fed into a gravel chute or tremie to completely fill the annular void outside the well casing to the top gravel pack level.

(3) Chlorine must be added to the well, after the activity described in subdivision (2), and circulated until a chlorine concentration of not less than fifty (50) mg/l in the entire volume of fluid is achieved.

(c) Immediately before placement in the void caused by settled gravel in a well, replacement gravel must be soaked in a chlorine solution of at least fifty (50) mg/l for a duration not less than thirty (30) minutes during initial construction or subsequent repairs.

(d) Permanent equipment and material used in a production well must be chlorinated before installation by spraying exposed areas with a solution containing a chlorine residual of not less than two hundred (200) mg/l.

(e) A new or modified well proposed to be a production well must be chlorinated in accordance with one (1) of the following:

(1) The water in the well casing must be treated with a disinfectant as follows:

(A) To create a chlorine residual of one hundred (100) mg/l to the entire volume of water in the casing, well screen, and rock hole, if present.

(B) The well must be:

(i) chlorinated using the compound requirements in Table 24-1; and

(ii) surged at least three (3) times after chlorination.

(C) The chlorinated water must remain in the well casing at least twelve (12) hours after the surging activity of clause (B)(ii).

(2) The water in the well casing must be treated with a disinfectant as follows:

(A) To create a chlorine residual of fifty (50) mg/l to the entire volume of water in the casing, well screen, and rock hole, if present.

(B) The well must be:

(i) chlorinated using the compound requirements in Table 24-1; and

(ii) surged at least three (3) times after chlorination.

(C) The chlorinated water must remain in the well casing at least twenty-four (24) hours after the surging activity of clause (B)(ii).

The following table demonstrates the amount of disinfectant needed for chlorination of wells:

Notes:

¹Quantities of Ca (OCl)₂ based on 65 percent (65%) available chlorine by dry weight (16 oz = 1 lb).

²Quantities of NaOCl based on 12 trade percent available chlorine by U.S. liquid measure (1 gal = 4 qt = 8 pt = 128 fl oz).

^‡"Trade percent" is a term used by chlorine manufacturers; trade percent × 10 = grams of available chlorine in 1 liter of solution.

(f) After disinfection is accomplished in accordance with subsection (e), a new or modified PWS production well and a flowing well must be sampled for the presence of coliform at least twice, with sampling done not less than twenty-four (24) hours apart, by a laboratory certified by the Indiana department of health or the United States Environmental Protection Agency using methods specified in 40 CFR 141.21*. If the presence of coliform is indicated by the sample results, the disinfection of the well must be repeated.

(g) Disposal of chlorinated water from well disinfection must be to one (1) of the following:

(1) A sanitary sewer with the approval of the local sewer authority.

(2) A location other than a sanitary sewer in accordance with local, state, and federal regulations.

*This document is 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, IN 46204.

(Water Pollution Control Division; 327 IAC 8-3.4-24; filed Jun 17, 1999, 1:50 p.m.: 22 IR 3377; readopted filed Jan 10, 2001, 3:23 p.m.: 24 IR 1518; filed Apr 24, 2006, 3:00 p.m.: 29 IR 2969; readopted filed Nov 21, 2007, 1:16 p.m.: 20071219-IR-327070553BFA; readopted filed Jul 29, 2013, 9:21 a.m.: 20130828-IR-327130176BFA; readopted filed Jun 14, 2019, 1:59 p.m.: 20190710-IR-327190246BFA; readopted filed Oct 18, 2024, 1:57 p.m.: 20241113-IR-327230810RFA; filed Nov 24, 2025, 9:07 a.m.: 20251224-IR-327240428FRA)