Inventory Variations. 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: Inventory variations exceeding 1 percent plus 130 gallons of the metered quantity of a regulated substance each calendar month; and Daily inventory records that show 7 consecutive days of shortage totaling 80 gallons or more. An owner and an operator of a UST system shall conduct a review of reconciled inventory records at the following frequencies: Review inventory variation as required under §A(1)(a) of this regulation monthly; and Review daily inventory records as required under §A(1)(b) of this regulation daily. Reporting and Investigating Inventory Variations. 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; 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; 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 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. The Department may require an owner and an operator of a UST system to perform a precision tightness test of the UST system: 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; If the owner and the operator fail to comply with monthly release detection requirements of Regulation .05 of this chapter; or For any other good cause as determined by the Department. 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.