Sec. 26.10.03.04. UST System Installation

A. All tanks and piping shall be properly installed in accordance with:

(1) The codes incorporated under COMAR 26.10.02.06A, B, C, and H;

(2) The manufacturer's instructions;

(3) COMAR 26.10.06; and

(4) Alternative installation methods determined by the Department to be as protective of human health and the environment.

B. Two permanent monitoring pipes shall be installed vertically and in opposing corners of new or replacement storage system installations unless the storage system is constructed in a high risk groundwater use area, as defined in COMAR 26.10.02.03, for which four monitoring pipes are required. The monitoring pipes shall:

(1) Extend to a minimum depth of 2 feet below the bottom of the tanks in the tank field;

(2) Be constructed of schedule 40 PVC;

(3) Be a minimum of 4 inches in diameter;

(4) Be screened from the bottom to within 2 feet of ground surfaces with the remaining 2 feet being solid PVC;

(5) Have a minimum slot size of 0.020 inch and maximum slot size of 0.025 inch with not less than 30 slots per foot;

(6) Be completed by:

(a) Backfilling around the outside with fine pea gravel or wrapping the pipe in an appropriate filter cloth to prevent clogging, and

(b) Sealing around the top 8 inches to ground surface with a bentonite clay, concrete mixture, or other means to prevent the entrance of surface runoff;

(7) Be capped by a liquid-tight threaded cap or removable liquid-tight plug and protected from traffic by manhole and cover;

(8) Be locked or bolted closed and identified to avoid confusion with product fill lines; and

(9) Have a key or locking tool for the monitoring pipes which shall be kept at the tank site.

C. Excavations.

(1) The tank excavation shall be a minimum distance of 5 feet from the base of adjacent structures or property lines.

(2) For steel tanks, excavations shall have a minimum 12-inch distance between tanks and 12-inch clearance between the tanks and all sides of the excavation.

(3) For fiberglass-reinforced plastic tanks, excavations shall have a minimum 18-inch distance between tanks and 18-inch clearance between the tanks and all sides of the excavation.

D. Tanks shall be placed upon a 12-inch bedding of backfill.

E. Backfill Material.

(1) Backfill material shall be:

(a) Pea gravel not larger than 3/4 inch; or

(b) Crushed stone not larger than 1/2 inch.

(2) Clean sand may be used for protected steel and steel-clad tanks.

(3) The same material used for bedding shall also be used for backfilling operations.

(4) There may not be debris or foreign or frozen matter in the backfill.

F. Except where there are 48 inches of clearance between the tanks and all shoring, shoring shall be removed from the tank excavation at the completion of the UST system installation.

G. In areas of high ground water or where tank movement is possible, underground storage tanks shall be safeguarded against movement from high ground water or flood by anchoring, or by other means acceptable to the Department and in compliance with tank manufacturer instructions.

H. When a hold-down pad or anchors made of concrete are used to prevent the movement of an underground storage tank, the new tank and associated backfill cannot be placed on freshly poured concrete or anchored to the hold-down devices until the concrete has cured for 48 hours.

I. A groundwater drain system may not be installed in a tank excavation area without prior written approval by the Department.