Before applying for an extension for temporary closure or completing a permanent closure or change-in-service of a UST system, an owner and an operator of a UST system shall: Perform a site assessment to determine if there is evidence of a spill, release, or discharge where contamination would most likely be present; and In selecting sample types, sample locations, and measurement methods consider: The method of closure; The nature of the stored regulated substance; The type of backfill; The depth to groundwater; and Other factors appropriate for identifying the presence of a spill, release, or discharge. If contaminated soil, contaminated groundwater, free product, or vapor is discovered while performing the actions under §A of this regulation or by any other manner during a UST system closure or change-in-service activities, an owner, an operator, and a person in charge of a UST system shall: Notify the Department within 2 hours of the discovery, as required in COMAR 26.10.08; and Begin performing the response and corrective actions required in COMAR 26.10.09.