1. (a) Requirements for release detection equipment. The owner or operator of an UST system shall ensure that equipment used for release detection complies with and is operated in accordance with the following requirements:

   1. (1) The release detection equipment shall be:

      1. (A) Able to detect a release from any portion of the UST system that routinely contains product;
      2. (B) Installed and calibrated in accordance with the instructions from the manufacturer of the release detection equipment;
      3. (C) Operated and maintained in accordance with the following, provided the requirements are no less stringent than the provisions of this section:

2. (i) The instructions from the manufacturer of the release detection equipment; or(ii) A code of practice developed by a nationally recognized association or independent testing laboratory;

   1. (D) Capable of detecting the leak rate or quantity with a probability of detection of 0.95 and a probability of false alarm of 0.05;

   2. (2) The owner or operator shall test the electronic and mechanical components of such release detection equipment for proper operation at least once annually. The annual test shall:

      1. (A) Be performed in accordance with:
3. (i) The instructions from the manufacturer of the release detection equipment; or(ii) A code of practice developed by a nationally recognized association or independent testing laboratory; and(B) Include the following UST system components and test criteria if utilized as part of the UST system:

4. (i) Automatic tank gauging and other controllers. The owner or operator shall test alarm(s); verify system configuration; and test battery backup;

   1. (ii) Probes and sensors. The owner or operator shall inspect for residual buildup; ensure floats move freely; ensure shaft is not damaged; ensure cables are free of kinks and breaks; and test alarm operability and its communication with controller;
   2. (iii) Automatic line leak detector. The owner or operator shall test operation to meet criteria in subsection (b)(4) of this section by simulating a leak; and(iv) Vacuum pumps and pressure gauges. The owner or operator shall ensure proper communication with sensors and controller.
   3. (C) If an annual test reveals that any release detection equipment is not functioning properly, the owner or operator shall:
5. (i) Comply with the requirements of section 22a-449(d)-105 of the UST regulations; and(ii) (I) Immediately repair or replace all malfunctioning equipment; or(II) Remove all regulated substances from such UST system so that no more than 2.5 centimeters (one inch) of such substances, or residue from such substances, remain in the UST system and, not later than 90 days after the test revealing malfunctioning release detection equipment is performed, repair or replace all malfunctioning equipment or begin permanent closure of such UST system; and(3) For a petroleum UST, daily measurements for any water level in the bottom of the tank to the nearest one-eighth of an inch shall be taken and recorded. Measurements that detect a loss or gain of water exceeding 0.5 percent of the volumetric capacity of the tank shall constitute a failure. This subdivision shall not apply to a double walled UST conducting interstitial monitoring in accordance with subsections (b)(1)(B) and (b)(1)(C) of this section.

6. (b) Release detection requirements for petroleum UST systems.The owner or operator of a petroleum UST system shall provide release detection for tanks and piping as follows:

   1. (1) Methods of Release Detection for Double-Walled Petroleum USTs. The owner or operator of a petroleum UST system with a double-walled UST shall use interstitial monitoring that complies with the requirements of this subdivision:

      1. (A) For a double-walled UST installed before October 1, 2003, the owner or operator shall perform release detection using any method that complies with the requirements of this subsection, provided that on or after May 7, 2027, such owner or operator shall use monitoring that complies with subparagraphs (B) or (C) of this subdivision.
      2. (B) For a double-walled UST installed on or after October 1, 2003, but before May 7, 2025, the release detection shall continuously monitor the interstitial space between the walls of the UST or comply with subparagraph (C) of this subdivision.
      3. (C) For a double-walled UST installed on or after August 5, 2025, the release detection shall continuously monitor the integrity of the walls of the tank for a potential failure of the primary and the secondary containment such that both the inner and outer walls of such tank, are monitored using technology such as inert gas, liquid, or a vacuum.

   2. (2) Methods of Release Detection for Single-Walled Petroleum USTs. Except as provided for in subdivision (3) of this subsection, the owner or operator of a petroleum UST system with a single-walled UST shall use automatic tank gauging with inventory control that complies with the following requirements.

      1. (A) For automatic tank gauging with inventory control:

7. (i) Perform an automatic product level monitor test that can detect a 0.2 gallon per hour leak rate from any portion of each tank that routinely contains product. This test shall be conducted and passed at least once every 30 days; and(ii) Have an inventory control method that:

   1. (I) Accurately records, on a daily basis, the amount of regulated substances removed from and added to the tank or interconnected tanks, the level of water and petroleum in the UST, and ensures that the measurement of any water level in the bottom of the tank is made to the nearest one-eighth of an inch;

      1. (II) Reconciles the daily readings on a weekly basis per tank or interconnected tanks to determine whether an abnormal loss or gain has occurred in accordance with subparagraph (B) of this subdivision. Such reconciliation shall be recorded on a form prescribed by the commissioner or a form that contains the information on the form prescribed by the commissioner;
      2. (III) Uses equipment capable of measuring the level of water and petroleum in the tank to the nearest one-eighth of an inch;
      3. (IV) Ensures that deliveries of petroleum are made through a drop tube that extends to within one foot of the tank bottom and by May 7, 2026, such drop tube shall extend no more than six inches from the tank bottom; and(V) Measures and verifies all amounts of petroleum delivered into the tank by comparing delivery receipts with measurements of the tank inventory volume immediately before and immediately after delivery.
   2. (B) When a weekly reconciliation indicates an abnormal loss or gain, the owner or operator shall immediately investigate and correct the source of the abnormal loss or gain and take as many of the steps listed in this subparagraph as are necessary to determine the source of the abnormal loss or gain. If, after taking such steps, the source of such abnormal loss or gain has not been identified, then the owner or operator shall comply with the requirements of subparagraph (C) of this subdivision.

8. (i) When an inventory record error is not apparent, perform a recalculation to determine whether an abnormal loss or gain has occurred using existing inventory records starting from the point where such records do not indicate an abnormal loss or gain;

   1. (ii) Conduct a detailed visual inspection of the components of the UST system which are readily accessible for evidence of failure; and(iii) Check the dispensers associated with the UST for proper calibration.
   2. (C) The owner or operator shall perform a tank tightness test and a line tightness test, and any other test designated by the commissioner in writing to identify a release from the UST system if:

9. (i) A weekly reconciliation indicates an abnormal loss or gain and there were 4 consecutive days of loss or 4 consecutive days of gain during the 10-day period prior to reconciliation;

   1. (ii) An abnormal loss or abnormal gain is measured during 2 consecutive weekly reconciliations; or(iii) The owner or operator cannot identify the source of the abnormal loss or gain using the methods identified in subparagraph (B) of this subdivision.

   2. (3) Manual Tank Gauging for USTs Storing Used Oil.

      1. (A) Manual tank gauging may only be used as the method of release detection for an UST that contains 550 gallons or less of used oil.
      2. (B) The owner or operator using manual tank gauging shall ensure that:

10. (i) The water level in the bottom of the tank shall be measured daily. Such measurements shall be in increments of no more than one-eighth of an inch; and(ii) UST liquid level measurements, of all liquids in the tank, shall be taken and recorded, including date and time of measurements, at the beginning and ending of a period of at least 36 hours during which no used oil is added to or removed from the tank. The liquid level measurements shall be based on an average of 2 consecutive stick readings taken at both the beginning and ending of the period. Such measurements shall be in increments of no more than one-eighth of an inch. If such measurements detect a variation of 10 gallons a week or 5 gallons a month based on the average of 4 weekly tests, such variation shall constitute a failure and the owner or operator shall comply with section 22a-449(d)-105 of the UST regulations.

    1. (4) Pressurized Piping.

       1. (A) Underground piping that conveys or contains petroleum under pressure shall utilize an automatic line leak detector capable of detecting the presence of a release of 3 gallons per hour at 10 pounds per square inch line pressure within 1 hour and restricting or shutting off the flow of regulated substances through piping.
       2. (B) The owner or operator shall conduct an annual test of the automatic line leak detector in accordance with the manufacturer’s requirements, provided that there are at least 9 months between such tests. If an annual test reveals that equipment is not functioning, the owner or operator shall:

11. (i) Immediately repair or replace all malfunctioning equipment; and(ii) If the equipment malfunction could have prevented the UST system from detecting a release and if the piping associated with such UST system does not use interstitial monitoring, the owner or operator shall perform a line tightness test. If such UST system fails a line tightness test, the owner or operator shall comply with the requirements of section 22a-449(d)-105 of the UST regulations.

    1. (C) Except for piping utilizing continuous interstitial monitoring, pressurized piping shall be tested annually using a line tightness test capable of detecting a 0.1 gallon per hour leak rate at one and one-half times the operating pressure of such piping, provided there is at least 9 months between such tests. A measurement that detects a leak rate equal to or greater than 0.1 gallons per hour at one and one-half times the operating pressure of piping being tested shall constitute a failure; and(D) Pressurized piping installed on or after October 1, 2003 shall utilize interstitial monitoring that, at a minimum, has sensors at both ends of the piping run or a vacuum that provides continuous interstitial monitoring.

    2. (5) Suction piping.

       1. (A) The owner or operator shall ensure that underground piping that conveys or contains petroleum under suction shall be tested once every 3 years using a line tightness test capable of detecting a 0.1 gallon per hour leak rate at one and one-half times the operating pressure of such piping. A measurement that detects a leak rate equal to or greater than 0.1 gallons per hour at one and one-half times the operating pressure of piping being tested shall constitute a failure.
       2. (B) A line tightness test shall not be required for suction piping that:

12. (i) Utilizes interstitial monitoring that has a sensor capable of detecting a release or has a vacuum that provides continuous interstitial monitoring; or(ii) Is designed and constructed to meet the following standards and the owner or operator maintains documentation demonstrating that:

    1. (I) The piping is sloped so that the contents of the pipe drain back into the tank if the suction is released;

       1. (II) Only one check valve is included in each suction line; and(III) The check valve is located directly below and as close as practical to the suction pump.
    2. (C) Underground piping that conveys or contains petroleum under suction, installed on or after October 1, 2003, shall be double-walled and shall utilize interstitial monitoring that has a sensor capable of detecting a release or has a vacuum that provides continuous interstitial monitoring.

13. (c) Release detection requirements for hazardous substance UST systems.The owner or operator of a hazardous substance UST system shall provide release detection for tanks and piping as follows:

    1. (1) The interstitial space of the tank and piping used for secondary containment, depending upon date of installation, shall be:

       1. (A) Checked for equipment malfunctions, such as whether liquid is present, at least once every 30 days if the UST system was installed before October 1, 2003 and does not have continuous interstitial monitoring;
       2. (B) Continuously monitored using inert gas, liquid, a vacuum, electronic monitoring, or mechanical monitoring for a release from the primary containment, such as the inner wall, if the UST system was installed:

14. (i) On or after October 1, 2003, but before August 5, 2025; or (ii) Before October 1, 2003, if such system has continuous interstitial monitoring; or(C) Continuously monitored such that both the inner and outer walls of such tank are monitored using technology such as inert gas, liquid, or a vacuum if the UST system was installed on or after August 5, 2025.

    1. (2) For a hazardous substance UST system that utilizes underground piping that conveys or contains hazardous substances under pressure, the owner or operator shall conduct an annual test of the operation of the automatic line leak detector in accordance with subsection (b)(4) of this section.

15. (d) Additional UST system testing.

    1. (1) If the owner or operator fails to undertake release detection for an UST system in compliance with this section, the owner or operator shall perform a tank tightness test capable of detecting a 0.1 gallon per hour leak rate from any portion of the tank while accounting for the effects of thermal expansion or contraction of the product, vapor pockets, tank deformation, evaporation or condensation, and the location of the water table.
    2. (2) If the owner or operator fails to undertake release detection for piping in compliance with this section, and during such non-compliance the owner or operator would have been prevented from detecting a release, in addition to any other requirements of this section, the owner or operator shall perform a line tightness test capable at one and one-half times the operating pressure of such piping.
    3. (3) Any testing required by subdivision (1) or (2) of this subsection is in addition to any other testing required by the UST regulations and does not otherwise constitute compliance with any other testing requirement.
16. (e) Failures.If any monitoring, test, or check required by this section detects a malfunction, release, or a suspected release, unless otherwise specified in this section, the owner or operator of the UST system shall comply with section 22a-449(d)-105 of the UST regulations.

(Effective July 28, 1994; Amended May 7, 2025)