Not later than October 13, 2022, an owner and an operator of a UST system with a field-constructed tank or an airport hydrant system shall provide a method of release detection in accordance with the requirements of this regulation. Field-Constructed Tanks. An owner and an operator of a UST system with a field-constructed tank with a capacity less than or equal to 50,000 gallons shall meet the UST system release detection requirements in COMAR 26.10.05. An owner and an operator of a UST system with a field-constructed tank with a capacity greater than 50,000 gallons shall comply with the following release detection requirements: If a metered UST system, perform monthly inventory control in accordance with COMAR 26.10.05.04 or an equivalent procedure that can detect a leak less than or equal to 0.5 percent of the monthly flow-through; and Perform release detection in accordance with COMAR 26.10.05 or by using at least one of the following alternative methods of release detection: Conduct an annual tank tightness test that can detect a 0.5 gallon per hour (gph) leak rate; Use an automatic tank gauging system to perform monthly release detection that can detect a leak rate of less than or equal to 1.0 gph, and conduct a tank tightness test that can detect a 0.2 gph leak rate at least every 3 years; Use an automatic tank gauging system to perform monthly release detection that can detect a leak rate of less than or equal to 2.0 gph, and conduct a tank tightness test that can detect a 0.2 gph leak rate at least every 2 years; Perform vapor monitoring in accordance with §C(2)(b) of this regulation; Perform monthly inventory control in accordance with COMAR 26.10.05.04 or an equivalent procedure that can detect a leak less than or equal to 0.5 percent of the monthly flow-through, and in conjunction perform either a tank tightness test that can detect a 0.5 gph leak rate at least every 2 years or groundwater monitoring as a monthly method of release detection in accordance with COMAR 26.10.05.05F; or Perform another method of release detection approved by the Department if the owner and an operator of the UST system can demonstrate that the method can detect a spill, release, or discharge as effectively as any of the methods allowed under §B(2)(b)(i)—(v) of this regulation. Piping. An owner and an operator of a UST system with a field-constructed tank that has a capacity greater than 50,000 gallons or an airport hydrant system shall comply with the release detection requirements of this section if underground piping is associated with the field-constructed tank or the airport hydrant system. If the UST system is metered, the owner and the operator of the UST system shall perform monthly inventory control in accordance with COMAR 26.10.05.04 or an equivalent procedure that can detect a leak less than or equal to 0.5 percent of the monthly flow-through. The owner and the operator of the UST system shall perform a method of release detection provided in COMAR 26.10.05 or at least one of the alternative methods of release detection specified in paragraphs(a)—(d) of this subsection. Line Tightness Test. Perform a semiannual or annual line tightness test at or above the piping operating pressure in accordance with Table 1. If a piping segment with a volume of greater than or equal to 100,000 gallons is not capable of meeting the maximum 3.0 gph leak rate for a semiannual test, perform a line tightness test using a leak rate up to 6.0 gph in accordance with the schedule established in Table 2. Agency Note: The leak detection rate for a test section volume may not exceed the maximum leak detection rate identified for the corresponding semiannual test or annual test. Vapor Monitoring. Perform vapor monitoring for a tracer compound placed in the UST system that is capable of detecting a 0.1 gph leak rate at least every 2 years according to the following criteria: Test for the tracer compound within the soil gas of the excavation zone; Use materials as backfill that are sufficiently porous, such as gravel, sand or crushed rock, to readily allow diffusion of tracer compound vapors released from the UST system into the excavation zone; Place a tracer compound in the UST system that is sufficiently volatile to result in a vapor level that is detectable by the monitoring devices located in the excavation zone in the event the tracer compound vapors are released from the UST system; Use a method to detect tracer compound vapors that is not rendered inoperative by groundwater, rainfall, or soil moisture or other known interferences so that a release could go undetected for more than 30 days; Ensure that the level of background contamination in the excavation zone will not interfere with the method used to detect the tracer compound if released from the UST system; Use a method to detect tracer compound vapors in the excavation zone that is designed and operated to detect any significant increase in the concentration of the tracer compound vapor above background; In the excavation zone, assess the site to ensure compliance with the requirements §C(2)(b)(ii)—(v) of this regulation and to establish the number and positioning of testing locations that will detect tracer compound vapors released within the excavation zone from any portion of the UST system; and Clearly mark and secure the testing locations to avoid unauthorized access and tampering. Inventory Control. Perform monthly inventory control in accordance with COMAR 26.10.05.04 or an equivalent procedure that can detect a leak less than or equal to 0.5 percent of the flow-through and perform one of the following methods of release detection: Perform a line tightness test at least every 2 years in accordance with Table 1 of §C(2)(a)(i) of the regulation using the leak rates for the semiannual test; or Perform groundwater monitoring as a method of monthly release detection in accordance with COMAR 26.10.05.05F. An owner and an operator of a UST system with a field-constructed tank or an airport hydrant system may use another release detection method approved by the Department if the owner and an operator of the UST system can demonstrate that the method can detect a spill, release, or discharge as effectively as any of the methods allowed §C(2)(a)—(c) of this regulation. When comparing alternative methods of release detection for approval, as provided in §§B(2)(b)(vi) and C(2)(d) of this regulation, the Department shall consider the size of release that the method can detect and the frequency and reliability of detection. Recordkeeping for Release Detection. An owner and an operator of a UST system with a field-constructed tank or an airport hydrant system shall maintain release detection records in accordance with COMAR 26.10.05.06. Notifications. When a release detection method operated in accordance with this regulation indicates that a spill, release, or discharge may have occurred, an owner and an operator of a UST system with a field-constructed tank or an airport hydrant system shall notify the Department in accordance with COMAR 26.10.08.01. If an owner, an operator, and a person in charge of a UST system with a field-constructed tank or an airport hydrant 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.