Authority: IC 14-10-2-4; IC 14-37-3

Affected: IC 14-37

Sec. 21. (a) This section establishes requirements for setting a top plug in a well.

(b) An owner or operator must set a top plug beginning from a depth of at least fifty (50) feet below the lowermost underground source of drinking water and extending to a depth of three (3) feet below ground elevation.

(c) Within seventy-two (72) hours after setting a top plug under subsection (b), an owner or operator must confirm the level of the top of the cement inside the casing and outside the casing. If the cement top cannot be confirmed visually, the operator shall measure the depth to the top of the cement using a wireline or other suitable distance measuring method. The owner or operator must fill the casing and well annulus to within three (3) feet of the ground elevation with cement or other plugging material as provided in subsection (d).

(d) When the cement top has fallen no more than one hundred (100) feet below ground elevation, the well may be filled with bentonite or cement poured from the surface into the well and the well annulus. However, if there is a column of water greater than ten (10) feet on top of the cement, cement must be placed using the circulation method.

(e) The use of bentonite chips under subsection (d) shall comply with the following:

1. (1) The bentonite shall be of a grade commercially marketed for use in sealing or plugging earthen bore holes.
2. (2) Unless authorized by the division of reclamation, the bentonite shall have a typical particle size of not less than three-eighths (3/8) inch. Unless the bentonite chips are compressed or specially coated to retard the rate of hydration when poured through standing water, the chips shall be screened prior to placement in the well to remove fine particles.
3. (3) When using bentonite chips to fill the annulus, the chips shall be poured directly into the annular space from the top of the well provided the hole diameter outside the annular space to be filled is at least one and one-half (1 1/2) inches greater than the outside diameter of the casing.
4. (4) The total volume of bentonite chips used shall be calculated to completely fill the intended top plug interval when fully hydrated. Sufficient water shall be placed into the well to ensure full hydration of the bentonite.
5. (5) Bentonite chips shall not be used in water containing an excess of twelve thousand (12,000) mg/L of total chlorides.
6. (6) Bentonite chips shall be poured into the well at a rate that prevents bridging in the well. It is recommended the chips be poured at a rate of two (2) to three (3) minutes per fifty (50) pound bag.

(f) To facilitate identifying the location of the plugged well in the future, if no surface casing or production casing remains in a well, the owner or operator must place a steel plate at least one-fourth (1/4) inch thick and not less than eight (8) inches in diameter at the top of the cemented well bore. The steel plate shall be encased or incorporated in the cement within one (1) foot of the top of the cement and approximately three (3) feet below ground elevation.

(Natural Resources Commission; 312 IAC 29-33-21; filed Dec 1, 2017, 10:35 a.m.: 20171227-IR-312160230FRA; readopted filed Jan 17, 2023, 1:53 p.m.: 20230215-IR-312220328RFA; errata filed Mar 18, 2026, 9:59 a.m.: 20260325-IR-312260094ACA)