(1) Owners and operators of hazardous substance UST systems must provide release detection that meets the following requirements:

(a) Release detection at existing UST systems must meet the requirements for petroleum UST systems in ARM 17.56.402. By December 22, 1998, all existing hazardous substance UST systems must meet the release detection requirements for new systems in (1)(b).

(b) Release detection at new hazardous substance UST systems must meet the following requirements as provided in 40 CFR 264.193, adopted by reference in this rule:

(i) secondary containment systems must be designed, constructed, and installed to:

(A) contain regulated substances released from the tank system until they are detected and removed;

(B) prevent the release of regulated substances to the environment at any time during the operational life of the UST system; and

(C) be checked for evidence of a release at least every 30 days.

(ii) double-walled tanks must be designed, constructed, and installed to:

(A) contain a release from any portion of the inner tank within the outer wall; and

(B) detect the failure of the inner wall.

(iii) external liners (including vaults) must be designed, constructed, and installed to:

(A) contain 100% of the capacity of the largest tank within its boundary;

(B) prevent the interference of precipitation or ground water intrusion with the ability to contain or detect a release of regulated substances; and

(C) surround the tank completely (i.e., it is capable of preventing lateral as well as vertical migration of regulated substances).

(iv) underground piping must be equipped with secondary containment that satisfies the requirements of (1)(b)(i) (e.g., trench liners, jacketing of double-walled pipe). In addition, underground piping that conveys regulated substances under pressure must be equipped with an automatic line leak detector in accordance with ARM 17.56.408(1). The department adopts and incorporates by reference 40 CFR 264.193, which sets forth standards for secondary containment and detection of releases of UST systems, a copy of which may be obtained from Superintendent of Documents, Government Printing Office, Washington, DC 20402, (202) 783-3238.