An owner and an operator of a UST system shall properly install the UST system in accordance with: The requirements of this regulation; The applicable technical codes and standards incorporated by reference under COMAR 26.10.01.03; The manufacturer’s instructions; The requirement to have a certified UST system technician perform or supervise the installation in accordance with COMAR 26.10.02.03D; and Any alternative installation methods approved by the Department under Regulations .01B(1)(d), .02B(1)(c), and .03C(1) of this chapter. Monitoring Pipes. An owner and an operator of a UST system shall: Install two permanent monitoring pipes or, if a UST system is constructed in a high risk groundwater use area or well head protection area as defined in COMAR 26.10.07.02B, four permanent monitoring pipes: Vertically and in opposing corners of a new or replacement UST system excavation zone; That extend to a minimum depth of 2 feet below the bottom of the UST in the excavation zone; Constructed of schedule 40 polyvinyl chloride (PVC); That are a minimum of 4 inches in diameter; Constructed with PVC screened pipe from the bottom to within 2 feet of the top of a monitoring pipe, with the remaining 2 feet being constructed of solid PVC; and That have a minimum slot size of 0.020 inches and maximum slot size of 0.025 inches with not less than 30 slots per foot; and Complete the installation of the monitoring pipes required under §B(1) of this regulation by: Backfilling around the outside of the monitoring pipes with fine pea gravel or wrapping the monitoring pipes in an appropriate filter cloth to prevent clogging; Sealing around the top 8 inches to ground surface with a bentonite clay and concrete mixture or by other means to prevent the entrance of surface water runoff; Capping the monitoring pipes with a liquid-tight threaded cap or removable liquid-tight plug; Protecting the monitoring pipes from traffic with a manhole and cover; Locking or bolting closed the monitoring pipes; Identifying the monitoring pipes to avoid confusion with product fill lines; and Having a key or locking tool for the monitoring pipes kept at the regulated substance storage facility. Excavations. An owner and an operator of a UST system shall perform an excavation for the UST system that is: A minimum distance of 5 feet from the base of adjacent structures or property lines; If installing a steel UST, a minimum 12-inch distance between other USTs and a minimum 12-inch clearance between a UST and all sides of the excavation zone; and If installing a fiberglass-reinforced plastic UST, a minimum 18-inch distance between other USTs and a minimum 18-inch clearance between a UST and all sides of the excavation zone. An owner and an operator of a UST system shall place a UST upon a minimum 12-inch bedding made of backfill material. Backfill Material. An owner and an operator of a UST system: Shall use backfill material composed of: Pea gravel not larger than 3/4 of an inch; or Crushed stone not larger than 1/2 of an inch; May use clean sand as backfill material for protected steel and steel-clad USTs; Shall use the same material for backfilling operations that is used for bedding; and May not use backfill material with debris, foreign matter, or frozen matter. Except where there is, at a minimum, 48 inches of clearance between a UST and shoring, an owner and an operator of a UST system shall remove shoring from the UST system excavation zone when the installation of the UST system is complete. In an area of high groundwater or where UST movement is possible, an owner and an operator of a UST system shall safeguard a UST against movement from high groundwater or a flood by: Anchoring the UST in compliance with the UST manufacturer’s instructions; or Other means acceptable to the Department. When using a hold-down pad or anchors made of concrete to prevent the movement of a UST, an owner and an operator of a UST system shall allow the concrete to cure for a minimum of 48 hours before: Placing a new UST and associated backfill on freshly poured concrete; or Anchoring a UST to the hold-down devices. An owner and an operator of a UST system may not install a groundwater drain system in the UST system excavation zone without prior written approval by the Department.