# COMAR Title 26 — Department of the Environment

## Subtitle 10 — Oil Pollution Control and Storage Tank Management

### Chapter 05 — UST Systems: Release Detection

**Authority:** Environment Article, §§4-401, 4-402, 4-405, 4-407—4-411.2, 4-415.1, 4-417, 4-701 et seq., and 7-201 et seq., Annotated Code of Maryland

**Administrative History:** Effective date: February 4, 1991 (18:2 Md. R. 151)

**Administrative History:** Chapter revised effective November 4, 1996 (23:22 Md. R. 1498)

**Administrative History:** Regulation .01 amended effective February 18, 2002 (29:3 Md. R. 224)

**Administrative History:** Regulation .01A amended effective January 12, 2009 (36:1 Md. R. 25)

**Administrative History:** Regulation .02B amended effective June 29, 1998 (25:13 Md. R. 997)

**Administrative History:** Regulation .02C amended effective January 16, 2006 (33:1 Md. R. 39)

**Administrative History:** Regulation .02D amended effective January 12, 2009 (36:1 Md. R. 25)

**Administrative History:** Regulation .04 amended effective January 12, 2009 (36:1 Md. R. 25)

**Administrative History:** Regulation .04B amended effective June 29, 1998 (25:13 Md. R. 997)

**Administrative History:** Regulation .04C amended effective February 18, 2002 (29:3 Md. R. 224); January 16, 2006 (33:1 Md. R. 39)

**Administrative History:** Regulation .06 amended effective January 16, 2006 (33:1 Md. R. 39)

**Administrative History:** Regulations .01—.06 repealed and new Regulations .01—.06 adopted effective June 13, 2022 (49:12 Md. R. 642)

#### Regulation .01 Release Detection: General Requirements for All UST Systems.

*COMAR 26.10.05.01*

A. An owner and an operator of a UST system shall provide a method, or combination of methods, of release detection that:

  (1) Can detect a spill, release, or discharge from any portion of the UST and the connected underground piping;

  (2) Is installed and calibrated in accordance with the manufacturer’s instructions;

  (3) Is operated and maintained in accordance with:

    (a) The manufacturer’s instructions;

    (b) A code of practice incorporated by reference under COMAR 26.10.01.03; or

    (c) Requirements determined by the Department to be not less protective of human health and the environment than §A(3)(a) or (b) of this regulation;

  (4) Meets the performance requirements in Regulations .02 and .05 of this chapter, or COMAR 26.10.12 for a UST system with a field-constructed tank or an airport hydrant system, as applicable, with performance claims verified by the manufacturer’s specifications; and

  (5) Is capable of detecting a leak at a rate or quantity specified in this chapter with a probability of detection of not less than 0.95 and a probability of false alarm of not more than 0.05.

B. Beginning January 12, 2009, an owner and an operator of a UST system installing a new or replacement UST system shall monitor the UST system for a spill, release, or discharge at least monthly by interstitial monitoring in accordance with Regulation .05G of this chapter.

C. Release Detection Operability Test. An owner and an operator of a UST system shall:

  (1) Have the electronic and mechanical components of a release detection method tested for proper operation in accordance with:

    (a) The manufacturer’s instructions;

    (b) A code of practice incorporated by reference under COMAR 26.10.01.03; or

    (c) Requirements determined by the Department to be not less protective of human health and the environment than §C(1)(a) or (b) of this regulation;

  (2) Perform an operability test of each electronic and mechanical component of a release detection method used at a regulated substance storage facility in accordance with the following criteria:

    (a) For the automatic tank gauge and other controllers:

      (i) Test the alarm;

      (ii) Verify the system configuration; and

      (iii) Test the battery backup;

    (b) For the probes and sensors:

      (i) Inspect the equipment for residual buildup;

      (ii) Ensure the floats move freely;

      (iii) Ensure the shafts are not damaged;

      (iv) Ensure the cables are free of kinks and breaks; and

      (v) Test the alarm operability and communication with the controller;

    (c) Test the operation of the automatic line leak detector to meet the criteria in Regulation .02D(2) of this chapter by simulating a leak;

    (d) Ensure the proper communication of the vacuum pumps and pressure gauges with the sensors and controller; and

    (e) Ensure the proper operation of the hand-held electronic sampling equipment associated with groundwater monitoring;

  (3) Perform the operability tests required by §C(1) and (2) of this regulation at least annually; and

  (4) Maintain the following records to show compliance with §C(1)—(3) of this regulation:

    (a) A list of each component tested;

    (b) Whether each component tested meets criteria specified or needs to have action taken; and

    (c) A description of any action taken to correct an issue.

D. Notifications.

  (1) An owner and an operator of a UST system shall notify the Department in accordance with COMAR 26.10.08.01 when a release detection method operated in accordance with one of the following performance standards indicates that a spill, release, or discharge may have occurred:

    (a) Regulation .05 of this chapter; or

    (b) If the UST system has a field-constructed tank or an airport hydrant system, COMAR 26.10.12.

  (2) If an owner, an operator, and a person in charge of a UST system changes the method of release detection used, the owner, the operator, and the person in charge of the UST system shall provide the Department written notification within 30 days of the change.

E. An owner and an operator of a UST system that cannot apply a method of release detection that complies with the requirements of this chapter shall close the UST system in accordance with procedures in COMAR 26.10.10.

F. An owner and an operator of a previously deferred UST system described in COMAR 26.10.02.01A(4)—(6) and COMAR 26.10.12 shall meet the requirements of this chapter not later than October 13, 2022.

G. A person may not tamper with, or render inaccurate, any monitoring device or method required to be maintained under this chapter.

#### Regulation .02 Requirements for UST Systems.

*COMAR 26.10.05.02*

A. An owner and an operator of a petroleum UST system or a hazardous substance UST system, unless otherwise provided in this regulation, shall provide release detection for USTs and piping as described in this regulation.

B. An owner and an operator of a UST system shall monitor the UST system for releases of a regulated substance by:

  (1) Conducting inventory control in accordance with Regulation .04 of this chapter; and

  (2) At least monthly, conducting one of the methods of release detection described in Regulation .05B—H of this chapter.

C. An owner and an operator of a UST system with a UST capacity of 550 gallons or less and that is not metered may use weekly manual tank gauging conducted in accordance with Regulation .05C of this chapter as a method of release detection.

D. Underground Piping.

  (1) An owner and an operator of a UST system shall monitor underground piping that routinely contains petroleum vapor or a regulated substance in accordance with §D(2)—(4) of this regulation.

  (2) Pressurized Piping.

    (a) An owner and an operator of a UST system with underground piping that conveys regulated substances under pressure shall equip the underground piping with an automatic line leak detector that is tested annually in accordance with Regulation .01C of this chapter, and which will:

      (i) Alert the operator to the presence of a leak or a spill, release, or discharge by restricting or shutting off the flow of a regulated substance through piping or triggering an alarm; and

      (ii) Detect a leak or a spill, release, or discharge of a regulated substance of at least 3 gallons per hour at 10 pounds per square inch line pressure within 1 hour; and

    (b) An owner and an operator of a UST system with underground piping that conveys regulated substances under pressure shall:

      (i) At least annually, perform a precision tightness test on the piping for a minimum of 1 hour that is capable of detecting a 0.1 gallon per hour release at 1.5 times the pipe operating pressure; or

      (ii) At least monthly, perform one of the methods of release detection described in Regulation .05B and F—H of this chapter.

  (3) Suction Piping.

    (a) An owner and an operator of a UST system with underground piping that conveys regulated substances under suction shall:

      (i) At least every 2 years, perform a precision tightness test on the piping for a minimum of 1 hour that is capable of detecting a 0.1 gallon per hour release at a pressure between 5 and 15 pounds per square inch; or

      (ii) At least monthly, monitor for a spill, release, or discharge using one of the methods of release detection described in Regulation .05B and F—H of this chapter.

    (b) An owner and an operator of a UST system with underground suction piping are not required to perform the release detection and precision tightness testing required in §D(3)(a) of this regulation on the piping when:

      (i) The piping operates at less than atmospheric pressure;

      (ii) The piping is sloped so that the contents of the pipe will drain back into the UST if the suction is released;

      (iii) A single check valve is included in each suction line;

      (iv) The check valve is located directly below and as close as practicable to the suction pump; and

      (v) The owner and operator of the UST system provide a method of visual inspection to determine compliance with §D(3)(b)(ii)—(iv) of this regulation.

  (4) An owner and an operator of a UST system with secondary containment piping shall test that piping:

    (a) After completing installation of the piping but before operation of the UST system, for new, upgraded, or replaced piping;

    (b) At least every 5 years, for piping installed on or after January 12, 2009; and

    (c) In accordance with manufacturer’s specifications or a method approved by the Department.

#### Regulation .03 Requirements for Hazardous Substance UST Systems.

*COMAR 26.10.05.03*

A. In addition to the UST system requirements in Regulation .02 of this chapter, an owner and an operator of a hazardous substance UST system shall:

  (1) Provide containment that meets the requirements of this regulation; and

  (2) Monitor the containment systems using interstitial monitoring pursuant to Regulation .05G of this chapter at least monthly.

B. An owner and an operator of a hazardous substance UST system shall ensure the hazardous substance UST system meets the following requirements:

  (1) A secondary containment system is designed, constructed, and installed to:

    (a) Contain hazardous substances spilled or released from the primary containment until the spill or release is detected and removed;

    (b) Prevent the spill, release, or discharge of hazardous substances to the environment at any time during the operational life of the UST system; and

    (c) Be checked for evidence of a spill, release, or discharge at least monthly;

  (2) A double-walled UST is designed, constructed, and installed to:

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

    (b) Detect the failure of the inner wall;

  (3) An external liner, including a vault, is designed, constructed, and installed to:

    (a) Contain 100 percent of the capacity of the largest UST within its boundary;

    (b) Prevent precipitation or groundwater from entering the liner; and

    (c) Surround the UST completely;

  (4) Underground piping is equipped with secondary containment that satisfies the requirements of §B(1)—(3) of this regulation; and

  (5) Underground piping that conveys hazardous substances under pressure is equipped with an automatic line leak detector in accordance with Regulation .02D(2) of this chapter.

C. An owner and an operator of hazardous substance UST system may use other methods of release detection in conjunction with interstitial monitoring as required in §A(2) of this regulation if the owner and an operator of the UST system:

  (1) Demonstrates to the Department in writing that an alternate method can detect a release of the stored hazardous substance as effectively as any of the methods allowed in Regulation .05B—H of this chapter,

  (2) Provides the Department with information regarding effective corrective action technologies, health risks, and chemical and physical properties of the stored hazardous substance, and the physical characteristics of the regulated substance storage facility; and

  (3) Obtains approval from the Department to use the alternate release detection method before the installation and operation of the UST system.

#### Regulation .04 Inventory Control.

*COMAR 26.10.05.04*

A. Inventory Variations.

  (1) An owner and an operator of a UST system shall review the reconciled inventory records required by COMAR 26.10.04.01 for the following:

    (a) Inventory variations exceeding 1 percent plus 130 gallons of the metered quantity of a regulated substance each calendar month; and

    (b) Daily inventory records that show 7 consecutive days of shortage totaling 80 gallons or more.

  (2) An owner and an operator of a UST system shall conduct a review of reconciled inventory records at the following frequencies:

    (a) Review inventory variation as required under §A(1)(a) of this regulation monthly; and

    (b) Review daily inventory records as required under §A(1)(b) of this regulation daily.

  (3) Reporting and Investigating Inventory Variations.

    (a) An operator of a UST system shall report a variation or shortage as described in §A(1) of this regulation to the owner of the UST system;

    (b) Upon discovery of an inventory variation, an owner and an operator of a UST system shall immediately investigate the cause of the variation or shortage;

    (c) If the investigation required under §A(3)(b) of this regulation reveals no indication of a discharge or release from a UST system, an owner and an operator of a UST system shall state the cause of the inventory variation or shortage in the daily inventory records; and

    (d) If the investigation required under §A(3)(b) of this regulation reveals a discharge or release from a UST system, an owner and an operator of a UST system shall follow the procedures established under COMAR 26.10.08.

B. The Department may require an owner and an operator of a UST system to perform a precision tightness test of the UST system:

  (1) If the owner and the operator fail to reconcile daily inventory records as specified in COMAR 26.10.04.01 and review the reconciled records in accordance with §A of this regulation;

  (2) If the owner and the operator fail to comply with monthly release detection requirements of Regulation .05 of this chapter; or

  (3) For any other good cause as determined by the Department.

C. The Department may require an owner and an operator of a UST system to perform a precision tightness test of the UST system and install monitoring wells or conduct a site assessment if there is reason to believe there is or may have been a discharge or release of a regulated substance from the UST system.

#### Regulation .05 Method of Release Detection.

*COMAR 26.10.05.05*

A. In addition to the inventory control requirements in Regulation .04 of this chapter, an owner and an operator of a UST system shall perform one or a combination of the methods of release detection described in §§B—H of this regulation at least monthly.

B. Statistical Inventory Reconciliation. An owner and an operator of a UST system utilizing statistical inventory reconciliation as a monthly method of release detection:

  (1) May only use statistical inventory reconciliation if the UST system is a metered UST system;

  (2) Shall use statistical inventory reconciliation to detect a spill, release, or discharge through application of statistical principles to inventory data, or another test of equivalent performance, with a probability of detection of not less than 0.95 and a probability of false alarm of not more than 0.05;

  (3) Shall use a method of statistical inventory reconciliation that meets the following requirements:

    (a) Uses inventory volume measurements collected in accordance with COMAR 26.10.04.01;

    (b) Produces a quantitative result with a calculated leak rate;

    (c) Is capable of detecting:

      (i) A leak rate of 0.2 gallon per hour; or

      (ii) A spill, release, or discharge of 150 gallons within a month; and

    (d) Uses a threshold that does not exceed one-half the minimum detectible leak rate; and

  (4) Shall have a Department-approved third party conduct the statistical inventory reconciliation.

C. Manual Tank Gauging.

  (1) At least weekly, an owner and an operator of a UST system shall perform manual tank gauging using a storage tank gauging stick maintained in accordance with COMAR 26.10.04.01 as follows:

    (a) Take UST liquid level measurements at the beginning and ending of an at least 36-hour period, during which liquid may not be added to or removed from the UST;

    (b) Base the level measurements on an average of two consecutive stick readings at both the beginning and ending of the period; and

    (c) Using a UST gauge chart specific to the UST gauged, convert the liquid levels to the gallons present in the UST and review for any variations between the starting and ending measurements.

  (2) An owner and an operator of a UST system shall report a suspected spill, release, or discharge and follow the investigation and confirmation procedures in COMAR 26.10.08 if the variation between beginning and ending manual tank gauging measurements performed in accordance with §C(1) of this regulation exceeds the weekly or monthly standards in the following table:

  (3) An owner and an operator of a UST system may use manual tank gauging:

    (a) As the sole method of release detection if the nominal capacity of a UST is 550 gallons or less; and

    (b) For a UST with a nominal capacity of 551 to 2,000 gallons only in conjunction with conducting a precision tightness test, as defined in COMAR 26.10.02.02, at least every 5 years in accordance with the requirements of COMAR 26.10.03.05.

  (4) An owner and an operator of a UST system may not use manual tank gauging to meet the requirements of this chapter for a UST that has a nominal capacity of more than 2,000 gallons.

D. Precision Tightness Testing. At least monthly, an owner and an operator of a UST system shall conduct a precision tightness test, as defined in COMAR 26.10.02.02, as a method of release detection in accordance with the requirements of COMAR 26.10.03.05.

E. Automatic Tank Gauging. At least monthly, an owner and an operator of a UST system shall perform automatic tank gauging using equipment that tests for the loss of regulated substance and conducts inventory control and that meets the following requirements:

  (1) The automatic regulated substance level monitor test is capable of detecting a 0.2 gallon per hour leak rate from any portion of the UST;

  (2) The automatic tank gauging equipment meets the inventory control, or another test of equivalent performance, requirements of COMAR 26.10.04.01, and Regulation .04 of this chapter; and

  (3) An automatic tank gauging system tests for loss of a regulated substance by operating in one of the following modes:

    (a) In-tank static testing conducted at least once monthly; or

    (b) Continuous in-tank leak detection operating on an uninterrupted basis or operating within a process that allows the automatic tank gauging system to gather incremental measurements to determine the leak status of the UST at least once monthly.

F. Groundwater Monitoring.

  (1) Beginning June 13, 2022, an owner and an operator of a UST system may only use groundwater monitoring as a monthly method of release detection with prior written approval from the Department.

  (2) An owner and an operator of a UST system shall conduct groundwater monitoring in accordance with the following requirements:

    (a) Perform a site assessment 60 days before the implementation of the groundwater monitoring method;

    (b) Provide a written report of the site assessment to the Department upon request and, beginning June 13, 2022, ensure the written report is signed by a professional engineer or professional geologist, or equivalent licensed professional with experience in environmental engineering, hydrogeology, or other relevant technical discipline acceptable to the Department; and

    (c) Demonstrate that the testing or monitoring to detect a regulated substance on the groundwater meets all of the following requirements:

      (i) The regulated substance stored is immiscible in water and has a specific gravity of less than one;

      (ii) Groundwater is never more than 15 feet from the ground surface and the hydraulic conductivity of the soil or soils between the UST system and the monitoring wells or devices is not less than 0.01 centimeter/second, with the soil consisting of gravels, coarse to medium sands, coarse silts, or other permeable materials;

      (iii) The slotted portion of the monitoring well casing is designed to prevent migration of natural soils or filter pack into the well and to allow entry of regulated substance on the water table into the well under both high and low groundwater conditions;

      (iv) Monitoring wells are sealed from the ground surface to the top of the filter pack;

      (v) Monitoring wells or devices intercept the UST excavation zone or positioned as close to the excavation zone as is technically feasible;

      (vi) The method of measuring the contents of the well, whether automatic or manual, is capable of detecting the presence of at least 1/8 of an inch of free product on top of the groundwater in the monitoring wells;

      (vii) At least monthly, the contents of the groundwater monitoring well are measured;

      (viii) Within and immediately below the UST system excavation zone, the site is assessed to ensure compliance with the requirements in §F(2)(c)(i)—(v) of this regulation and to establish the number and positioning of monitoring wells or devices that will detect discharges or releases from any portion of the UST system;

      (ix) Monitoring wells are clearly marked and secured to avoid unauthorized access and tampering; and

      (x) A key, a lock combination number, or access tool for all monitoring wells is provided to the Department upon request and made available on the site where the UST system is located.

G. Interstitial Monitoring.

  (1) Beginning June 13, 2022, an owner and an operator of a UST system may only use interstitial monitoring as a monthly method of release detection between a UST system and a secondary barrier as described in §G(2)(b) of this regulation with prior written approval from the Department.

  (2) An owner and an operator of a UST system may use interstitial monitoring between the UST system and a secondary barrier immediately around or beneath the UST system as a method of release detection if the UST system is designed, constructed, and installed to detect a spill, release, or discharge from any portion of the UST system and one of the following conditions are met:

    (a) For a double-walled UST system, the owner and operator of the UST system uses a sampling or testing method that can detect a spill or release through the inner wall in any portion of the UST system;

    (b) For a UST system with a secondary barrier within the excavation zone, the owner or operator of the UST system uses a sampling or testing method that can detect a spill, release, or discharge between the UST system and the secondary barrier, provided that:

      (i) The secondary barrier around and beneath the UST system consists of artificially constructed material that is sufficiently thick and impermeable, at least 1×10-6 centimeter/second for the regulated substance stored, to direct a spill, release, or discharge to the monitoring point and allow the detection of the regulated substance;

      (ii) The barrier is compatible with the regulated substance stored so that a spill, release, or discharge from the UST system will not cause a deterioration of the barrier and allow a spill, release, or discharge to pass through the barrier undetected;

      (iii) For cathodically protected UST systems, the owner and the operator installs a secondary barrier so that it does not interfere with the proper operation of the cathodic protection system;

      (iv) The groundwater, soil moisture, or rainfall will not make the testing or sampling method used inoperative so that a spill, release, or discharge could go undetected for more than 30 consecutive days;

      (v) The site is assessed to ensure that the secondary barrier is always above the groundwater and not in a 25-year flood plain, unless the barrier and monitoring designs are for use under these conditions; and

      (vi) Monitoring wells are clearly marked and secured with bolts or a lock to avoid unauthorized access and tampering; and

    (c) For USTs with an internally fitted liner, the owner and operator of the UST uses an automated device that can detect a spill or release between the inner wall of the UST and the liner, and the liner is compatible with the regulated substance stored.

H. Other Methods.

  (1) Upon the approval of the Department, an owner and an operator of a UST system may use one or combination of alternative methods of monthly release detection if:

    (a) The method can detect a 0.2 gallon per hour leak rate or a release of 150 gallons within a month with a probability of detection of not less than 0.95 and a probability of false alarm of not more than 0.05; or

    (b) The owner and the operator of the UST system can demonstrate to the Department that the method can detect a spill, release, or discharge as effectively as any of the methods allowed in §§B and D—G of this regulation.

  (2) If an alternative method of monthly release detection proposed by an owner and an operator of a UST system is approved by the Department, the owner and the operator of the UST system shall comply with any conditions imposed by the Department on the use of the method to ensure the protection of human health and the environment.

I. Vapor Monitoring. Except as provided in §H of this regulation, an owner and an operator of a UST system may not use vapor monitoring as a monthly method of release detection after April 1, 2009.

#### Regulation .06 Release Detection Recordkeeping.

*COMAR 26.10.05.06*

A. An owner and an operator of a UST system shall maintain records demonstrating compliance with the applicable requirements of this chapter:

  (1) In accordance with COMAR 26.10.04.05;

  (2) For at least 1 year at the regulated substance storage facility;

  (3) For at least 5 years at a location designated by the owner of the UST system; and

  (4) That include the following information:

    (a) Written performance claims pertaining to any release detection system used, and the manner in which these claims have been justified or tested by the equipment manufacturer or installer;

    (b) The results of any sampling, testing, or monitoring including:

      (i) The results of annual operability tests required in Regulation .01C of this chapter; and

      (ii) The results of precision tightness testing conducted in accordance with Regulation .05D of this chapter; and

    (c) Written documentation for all calibration, maintenance, and repair of release detection equipment permanently located on-site, and any schedules of required calibration and maintenance provided by the release detection equipment manufacturer.

B. An owner and an operator of a UST system shall maintain records of site assessments required under Regulation .05F of this chapter for as long as the groundwater monitoring method is used.