Section 327IAC2-10-6. Storage outside a building

   (a) Aboveground storage tanks or storage areas containing hazardous materials that are located outside a building must have secondary containment.

  (b) Secondary containment must be designed and constructed consistent with current engineering standards with materials that are compatible with the hazardous materials being stored and which will prevent a release from entering waters of the state for a seventy-two (72) hour period. The design requirements of secondary containment must be met in one (1) of the following ways:

(1) A secondary containment area with dikes, berms, retaining walls, or trenches, and a floor that must cover the entire area within the dikes, berms, retaining walls, or trenches.

(2) A tank designed and built with an outer shell and an interstitial space between the tank wall and the outer shell that allows for monitoring.

(3) Diversionary systems that direct the discharges to treatment or temporary holding areas.

(4) Other methods approved by the commissioner that have been demonstrated to be equally protective of human health and the environment.

  (c) A secondary containment area must have a volume, considering displacement, to contain at least one hundred ten percent (110%) of the volume of the largest aboveground tank, or portable tank in the secondary containment area, or the volume of the largest aboveground tank, or portable tank plus enough freeboard to contain precipitation generated by a twenty-five (25) year/twenty-four (24) hour rain event. A tank designed and built with an outer shell for secondary containment is an acceptable alternative. At a minimum, secondary containment for storage areas holding only drums must be capable of holding or diverting one hundred twenty (120) gallons.

  (d) A secondary containment area must be properly maintained to protect the integrity and capacity of the secondary containment.

  (e) Liquid that collects within the secondary containment area must be removed within seventy-two (72) hours of its discovery in order to maintain the available capacity of the secondary containment area at one hundred percent (100%) of the largest aboveground tank, or portable tank in the secondary containment area. Ice must be removed as soon as weather permits. Liquid that collects within the secondary containment area must meet all applicable requirements of this article if discharged to waters of the state. (Water Pollution Control Division; 327 IAC 2-10-6; filed May 28, 1999, 11:42 a.m.: 22 IR 3101; errata filed Jun 8, 1999, 9:23 a.m.: 22 IR 3108; readopted filed Jan 10, 2001, 3:23 p.m.: 24 IR 1518; readopted filed Nov 21, 2007, 1:16 p.m.: 20071219-IR-327070553BFA; readopted filed Jul 29, 2013, 9:21 a.m.: 20130828-IR-327130176BFA)