Defining a High Risk Underground Oil Storage Facility. An oil storage facility is defined as a high risk underground oil storage facility under this chapter if the facility has: An underground storage capacity that includes: One or more UST systems constructed with a single-walled UST or single-walled product piping; and A total underground oil storage capacity of 80,000 gallons or greater, not including underground oil storage capacity used to store heating oil for onsite consumptive use; or As determined by a throughput review conducted in accordance with §A(2) of this regulation, a combined monthly oil throughput for all products stored in UST systems of: 750,000 gallons or more when averaged over a rolling 12-month period; or 1,000,000 gallons or more in any single month. Throughput Review Procedures. To determine if an underground oil storage facility meets the definition of a high risk underground oil storage facility on a throughput basis, an owner of an underground oil storage facility shall have a throughput review performed in accordance with §A(2)(b) of this regulation: At least once every three years during a certified inspection of a UST system required under COMAR 26.10.03.10; or If directed by the Department to perform a throughput review. Using a form provided by the Department, a certified UST system inspector or a person in charge of an underground oil storage facility performing a throughput review shall determine the combined monthly oil throughput for all products by evaluating inventory records that document: The average combined monthly oil throughput for all products over the preceding 12 months; and The highest combined monthly oil throughput for all products in the preceding 12 months. An owner of an underground oil storage facility shall submit to the Department the throughput review: As part of the inspection report required under COMAR 26.10.03.10D if the throughput review was performed during a certified inspection of a UST system; or As directed by the Department. An owner of a high risk underground oil storage facility may demonstrate that the oil storage facility no longer meets the definition of a high risk underground oil storage facility by submitting documentation, such as an updated throughput review, to the Department that proves the oil storage facility no longer meets the conditions under §A(1) of this regulation. Upon review of documentation provided to the Department pursuant to §A(3) of this regulation, the Department may determine: The oil storage facility no longer meets the definition of a high risk underground oil storage facility; and The owner of the oil storage facility is no longer required to comply with the requirements of this regulation. Compliance with Monitoring Methods. An owner of a high risk underground oil storage facility shall: Select, and upon receipt of Department approval, implement one of the following monitoring methods: Groundwater monitoring method specified under §C of this regulation; Enhanced testing method specified under §D of this regulation; or An alternative monitoring method specified under §E of this regulation; and Begin implementing the monitoring method in accordance with the following schedule: Within 6 months of June 13, 2022, if the facility meets the size and construction conditions of §A(1)(a) of this regulation; Within 6 months of determining that the facility meets the throughput conditions of §A(1)(b) of this regulation; or On a schedule determined by the Department. Groundwater Monitoring Method. An owner of a high risk underground oil storage facility choosing to implement the groundwater monitoring method shall: Install a minimum of three groundwater monitoring wells: That are constructed in accordance with the well construction requirements of COMAR 26.04.04 and Department specifications; Outside of the excavation zone; In locations that will allow for the determination of groundwater flow; and In areas that are most likely to detect a spill, release, or discharge from the UST system; Within 60 days of installing the groundwater monitoring wells, and annually thereafter: Sample each groundwater monitoring well and analyze collected samples: For full suite volatile organic compounds, including naphthalene and fuel oxygenates, in accordance with USEPA Test Method 8260 or another method approved by the Department; and For total petroleum hydrocarbons, including diesel and gasoline range organics, in accordance with USEPA Test Method 8015 or another method approved by the Department; and If present at the high risk underground oil storage facility, sample each site supply well and analyze collected samples for full suite volatile organic compounds, including naphthalene and fuel oxygenates, in accordance with USEPA Test Method 524.2 or another method approved by the Department; and Within 60 days after conducting a sample collection required under §C(2) of this regulation, submit the following documents to the Department: A complete laboratory report that includes a copy of the laboratory sample acceptance form, sample chain-of-custody, and laboratory analytical results; and A site map identifying each site supply well and groundwater monitoring well located at the oil storage facility. Enhanced Testing Method. This method may only be implemented by an owner of a high risk underground oil storage facility if all of the UST systems at the facility are installed with double-walled USTs and all of the piping systems are installed in accordance with COMAR 26.10.03.02A. An owner of a high risk underground oil storage facility choosing to implement the enhanced testing method shall: Perform UST and piping release detection by interstitial monitoring and perform at least one additional method of UST release detection in accordance with COMAR 26.10.05; Perform annual primary line precision tightness testing; Perform annual piping interstice precision tightness testing; Equip all containment sumps, except the vent riser containment sump, with sensors programmed for positive UST system dispensing and pumping shut down; and Every three years or at an alternative frequency under the direction of the Department, perform precision tightness testing of: The UST in a manner that minimizes isolation of UST system components, such as the vent and vapor piping and risers, to the greatest extent possible; and The UST interstice, except for a brine filled interstice. Alternative Monitoring Method. Subject to Department approval, an owner of a high risk underground oil storage facility may implement an alternative monitoring method if the owner demonstrates the alternative method is designed to detect a spill, release, or discharge from the UST system in a manner that is not less protective of human health and the environment than a method described under §C or D of this regulation. If an owner of a high risk underground oil storage facility detects a spill, release, or discharge at the facility, the owner shall comply with the spill, release, or discharge reporting and corrective action requirements of COMAR 26.10.08 and 26.10.09.