1. (1) A method, or combination of methods, of leak detection must be provided that:

   1. (i) can detect a leak from any portion of the tank and the piping that is in contact with the ground and routinely contains hazardous substance;
   2. (ii) is installed and calibrated in accordance with the manufacturer’s instructions; and
   3. (iii) meets the requirements of subdivisions (c) and (d) of this section, as applicable. In addition, the methods listed under paragraphs (c)(1), (d)(1), and (d)(2) of this section must be capable of detecting the leak rate or quantity specified for that method with a probability of detection of 95 percent and a probability of false alarm of 5 percent.

2. (2) If a method of leak detection that complies with the requirements of this section cannot be implemented, the UST system must be permanently closed in accordance with section 598-2.6(b) of this Subpart.

   (b) Specific leak detection requirements for tanks and piping.

3. (1) Tank leak detection. Every tank must be monitored for leaks at weekly intervals in accordance with paragraph (c)(2) of this section. Continuous electronic monitoring satisfies the weekly monitoring requirement.

4. (2) Piping leak detection. All piping in contact with the ground must be monitored for leaks at weekly intervals in accordance with paragraph (c)(2) of this section. Additionally, all piping in contact with the ground that conveys hazardous substance under pressure must be equipped with an automatic line leak detector that is operated in accordance with paragraph (d)(1) of this section.

   (c) Tank leak detection methods.

   Tank leak detection methods used to meet the requirements of paragraph (b)(1) of this section must be conducted in accordance with the following:

5. (1) Tank tightness testing.

   1. (i) A tightness test is a test acceptable to the department which will determine if a tank and piping system is tight or not tight. This shall include a test capable of detecting a tank leak of 1/10th gallons per hour (gph) with a probability of detection of 95 percent and probability of false alarm of five percent or less with a maximum threshold for declaring a leak of five hundredths of a gallon in one hour accounting for variables such as vapor pockets, thermal expansion and contraction of product, temperature stratification, groundwater level, evaporation, pressure and tank deformation.
   2. (ii) If it is technically impossible to perform a meaningful tightness test, then an alternative test or inspection which is acceptable to the department must be performed.
   3. (iii) Qualification of technicians. All tightness tests must be performed by a qualified technician who has an understanding of the variables which affect the test and is trained by the manufacturer or their representative to perform the test.

6. (2) Interstitial monitoring. Interstitial monitoring between the primary and secondary containment may be used if the monitoring equipment is designed, constructed and installed to detect a leak from any portion of the tank that routinely contains hazardous substance, and if the monitoring equipment meets the requirements of either subparagraph (i) or (ii) of this paragraph:

   1. (i) For a double-walled tank or double-walled piping, the sampling or testing method:

      1. (a) can detect a leak through the inner wall in any portion of the tank and/or piping that routinely contains hazardous substance; and
      2. (b) is capable of detecting a breach in both the inner and outer walls of the tank and/or piping if using continuous vacuum, pressure, or liquid-filled methods of interstitial monitoring.

   2. (ii) For a UST system with secondary containment within the excavation zone, the sampling or testing method can detect a leak between the primary and secondary containment, and the following conditions are met:

      1. (a) the secondary containment consists of artificially constructed material that is sufficiently thick and impermeable (i.e., with a permeability rate to water equal to or less than 1×10-6 cm/sec) to direct a leak to the monitoring point and permit its detection;
      2. (b) the secondary containment is compatible with the hazardous substance stored so that a leak from the UST system will not cause a deterioration of the secondary containment, allowing a leak to pass through undetected;
      3. (c) for cathodically protected tank systems the secondary containment must be installed so that it does not interfere with the proper operation of the cathodic protection system;
      4. (d) the groundwater, soil moisture, or rainfall will not render the testing or sampling method inoperative so that a leak could go undetected for more than seven days;
      5. (e) the site is assessed to ensure that the secondary containment is always above the groundwater and not in a 25-year flood plain, unless the secondary containment and monitoring designs are for use under such conditions;

      6. (f) Monitoring wells are clearly marked in accordance with section 598-2.2(b)(1)(v) of this Subpart and secured to avoid unauthorized access and tampering.

         (d) Piping leak detection methods.

         Piping leak detection methods used to meet the requirements of paragraph (b)(2) of this section must be conducted in accordance with the following:

7. (1) Automatic line leak detectors. Methods which indicate the presence of a leak by restricting or shutting off the flow of hazardous substance through piping, or triggering an audible or visual alarm, may be used only if they detect leaks of 3 gallons per hour at 10 pounds per square inch line pressure within one hour.

8. (2) Line tightness testing.

   1. (i) A tightness test is a test acceptable to the department which will determine if a tank and piping system is tight or not tight. This shall include a test capable of detecting a piping leak of one tenth gallons per hour (gph) with a probability of detection of 95 percent and probability of false alarm of five percent or less with a maximum threshold for declaring a leak of five hundredths of a gallon in one hour accounting for variables such as vapor pockets, thermal expansion and contraction of product, temperature stratification, groundwater level, evaporation, pressure and tank deformation.
   2. (ii) If it is technically impossible to perform a meaningful tightness test, then an alternative test or inspection which is acceptable to the department must be performed.

   3. (iii) Qualification of technicians. All tightness tests must be performed by a qualified technician who has an understanding of the variables which affect the test and is trained by the manufacturer or their representative to perform the test.

      (e) Recordkeeping.

      Records of the tests and inspections required by this section must meet the following requirements:

9. (1) The results or records of any sampling, testing, or monitoring must be retained for at least three years.

10. (2) The results of tank and line tightness testing must be retained for three years or until the next test, whichever is later, and include the following information:

    1. (i) facility registration number;
    2. (ii) tank system identification number as shown on the registration certificate for the tank or piping tested;
    3. (iii) date of test;
    4. (iv) results of test;
    5. (v) test method;
    6. (vi) certification by the technician that the test complies with paragraph (c)(1) or paragraph (d)(2) of this section;
    7. (vii) statement of technician’s qualifications;
    8. (viii) address of technician; and
    9. (ix) signature of technician.
11. (3) Written performance claims pertaining to any leak detection system used, and the manner in which these claims have been justified or tested by the equipment manufacturer or installer, must be retained for five years after the date of equipment installation.

12. (4) Written documentation of all calibration, maintenance, and repairs of leak detection equipment installed on-site must be retained for at least three years after the servicing work is completed. Schedules of required calibration and maintenance provided by the leak detection equipment manufacturer must be retained for five years after the date of equipment installation.

    (f) Uninspected tank systems.

    If any portion of a tank system is not tested or inspected as required by this section, the owner or operator must take the uninspected portion of the tank system out-of-service pursuant to the requirements of section 598-2.6(a) of this Subpart.

(a) General leak detection requirements.