Unless corrective action is initiated in accordance with COMAR 26.10.09, an owner and an operator of a storage tank system and a responsible party shall use the steps described in §§B and C of this regulation, or other procedures required by the Department to: Immediately but not later than 48 hours from the time a suspected spill, release, or discharge is discovered under Regulation .01 of this chapter or from the time an owner and an operator of a storage tank system and a responsible party is directed by the Department under Regulation .02 of this chapter, investigate a suspected spill, release, or discharge of a regulated substance; and Within 7 days of beginning the investigation, or another time period specified by the Department, confirm: All suspected spills, releases, and discharges of regulated substances requiring reporting under Regulation .01 of this chapter; and The source of off-site impacts if directed by the Department, as required under Regulation .02 of this chapter. System Test. An owner and an operator of a storage tank system and a responsible party shall conduct a system test to determine whether a leak exists in the storage tank, the piping, the secondary containment, or another component of the storage tank system by conducting: Precision tightness testing in accordance with COMAR 26.10.03.05; As appropriate, secondary containment testing in accordance with COMAR 26.10.04.04D; or A testing procedure required by the Department. When a storage tank system fails a system test required by §B(1) of this regulation or another test for tightness, an owner and an operator of a storage tank system and a responsible party shall take the following steps: Immediately discontinue use of the storage tank system and notify the Department; Within 48 hours, begin an investigation to determine whether the leak is occurring in the storage tank, the piping, the secondary containment, or another component of the storage tank system; If the storage tank is determined to be leaking, immediately remove the regulated substance from the storage tank; If the piping system is determined to be leaking, immediately drain and discontinue the use of the piping system; If the system test confirms a release into the interstice or a spill, release, or discharge to the environment: Repair the storage tank system in accordance with COMAR 26.10.04.04; Replace or upgrade the storage tank system in accordance with COMAR 26.10.03; or Close the storage tank system in accordance with COMAR 26.10.10; If another component of the storage tank system is determined to be leaking, perform the necessary repairs to the storage tank system in accordance with COMAR 26.10.04.04 within a time period approved by the Department; and After repairing or replacing the storage tank system and before placing the storage tank system back in service, conduct a system test on the storage tank system in accordance with §B(1) of this regulation to verify that the condition that caused the original test failure has been corrected. In addition to complying with the steps in §B(2) of this regulation, an owner and an operator of a storage tank system and a responsible party shall begin corrective action in accordance with COMAR 26.10.09 if the system test results for the storage tank system, storage tank, or piping indicate the existence of a spill, release, or discharge to the environment. An owner and an operator of a storage tank system and a responsible party are not required to conduct further investigation if the system test results for the storage tank system, storage tank, and piping do not indicate the existence of a spill, release, or discharge and environmental contamination was not the basis for suspecting a spill, release, or discharge. An owner and an operator of a storage tank system and a responsible party shall conduct a site check as described in §C of this regulation if the system test results for the storage tank system, storage tank, and piping do not indicate the existence of a spill, release, or discharge, but environmental contamination was the basis for suspecting a spill, release, or discharge. Site Check. An owner and an operator of a storage tank system and a responsible party shall measure for the presence of a spill, release, or discharge where contamination is most likely to be present. In selecting sample types, sample locations, and measurement methods, an owner and an operator of a storage tank system and a responsible party shall consider: The nature of the stored substance; The type of initial alarm or cause for suspicion; The type of backfill; The depth to groundwater; and Other factors appropriate for identifying the presence and source of a spill, release, or discharge. If the test results for the excavation zone or the site indicate that a spill, release, or discharge has occurred, an owner and an operator of a storage tank system and a responsible party shall begin corrective action in accordance with COMAR 26.10.09. If the test results for the excavation zone or the site do not indicate that a spill, release, or discharge has occurred, the Department will determine if further investigation is required. If required by the Department, an owner and an operator of a storage tank system and a responsible party shall construct observation, monitoring, and recovery wells: In compliance with COMAR 26.04.04; Of polyvinylchloride or another material approved by the Department; With a proper grout seal and locking cap; and As required in an approved corrective action plan developed in accordance with COMAR 26.10.09.07.