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Maryland operates an OSHA-approved State Plan covering most private sector workers and all state and local government workers. The Maryland Occupational Safety and Health (MOSH) State Plan is part of the Maryland Division of Labor and Industry.
MOSH has adopted all federal OSHA standards that would relate to public and private sector employer operations, which are incorporated by reference. In addition, MOSH has adopted unique standards for excavation and requirements for protective systems.
The intent of these excavation standards is to protect underground facilities to prevent death or injury to individuals, private and public property damage, and loss of services provided to the public.
These standards do not apply to an excavation six inches or less in depth or demolition performed by an owner or lessee of a private residence when the excavation or demolition is performed entirely on the land on which the private residence of the owner or lessee is located and without the use of machinery.
Marking requirements
Location of markings. An owner-member or its contract locator must mark its underground facility if a proposed excavation or demolition that is specified in the extent of work contained in the ticket:
- Is within 5 feet of the horizontal plane of the underground facility; or
- Because of planned blasting, is so near to the underground facility that the underground facility may be damaged or disturbed.
An owner-member or its contract locator must mark the location of its underground facility by marking on the ground within 18 inches on a horizontal plane on either side of the underground facility.
Use of color codes. When marking the location of an underground facility, an owner-member or its contract locator must use the color codes established by the American Public Works Association for marking underground facilities. If two or more owner-members share the same color code, each owner-member or its contract locator must include information with the marking that indicates the owner-member of the marked underground facility.
Due care requirement. A person performing an excavation or demolition must exercise due care to avoid interference with or damage to an underground facility that an owner-member or its contract locator has marked or where clear evidence of an unmarked underground facility exists.
Use of mechanized equipment. Before using mechanized equipment for excavation or demolition within 18 inches of an underground facility marking, a person must expose the underground facility to its outermost surfaces by hand or other nondestructive techniques.
Trenchless technology. When utilizing a trenchless technology method, to prevent the occurrence of a cross-bore, a person must expose by nondestructive techniques intersecting underground facilities to the depth of the excavation plus 18 inches in the path of the trenchless technology operation during the entire trenchless installation operation.
A person may not use mechanized equipment to excavate within 18 inches of the outermost surface of an exposed underground facility.
UST system installation standards (COMAR 26.10.03.04)
An owner and an operator of an underground storage tank (UST) system must properly install the UST system in accordance with:
- The requirements of COMAR 26.10.03.04;
- 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 of the Environment under regulations .01B(1)(d), .02B(1)(c), and .03C(1) of COMAR 26.10.03.
Monitoring pipes. An owner and an operator of a UST system must:
- 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 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; o 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 must perform an excavation for the UST system that is:
- A minimum distance of five 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.
Bedding. An owner and an operator of a UST system must place a UST upon a minimum 12-inch bedding made of backfill material.
Backfill material. An owner and an operator of a UST system:
- Must 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;
- Must 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.
Removal of shoring. 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 must remove shoring from the UST system's excavation zone when the installation of the UST system is complete.
High groundwater areas. In an area of high groundwater or where UST movement is possible, an owner and an operator of a UST system must safeguard a UST against movement from high groundwater or a flood by:
- Anchoring the UST in compliance with the UST manufacturer instructions; or
- Other means acceptable to the Department.
Use of hold-down pad or anchors. 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 must 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.
Groundwater drain installation. 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.
Piping installation (COMAR 26.10.03.06)
An owner and an operator of a UST system must install piping in accordance with the requirements of COMAR 26.10.03, including the following:
- Place underground piping on a 6-inch bedding of appropriate backfill material as described in COMAR 26.10.03.04.
- Maintain the following clearances when installing piping:
- Twice the nominal diameter of the pipe but at least 4 inches between all piping;
- At least 6 inches between piping and electrical conduits related to the UST system;
- At least 6 inches between piping and excavation zone sidewalls; and
- At least 18 inches between piping and the surface of the ground.
- Unless otherwise approved by the Department, ensure piping rises 1/8 of an inch for each lateral foot from the UST to the piping endpoint.
- Follow the manufacturer's specifications and installation requirements when installing piping.
- In accordance with manufacturer specifications, use a UL listed flexible connector to connect piping as follows:
- Except for a direct fill line, to connect a pipe carrying a regulated substance to a UST at the end of a piping run; and
- To connect a pipe carrying a regulated substance to a dispenser system.
- Unless otherwise approved by the Department, an owner and an operator of a UST system may not use a flexible connector to connect piping carrying petroleum vapor or a regulated substance at any other point in the piping system not listed above.
- Place a UL listed shear valve on pressurized product piping dispensing motor fuel and properly anchor the shear valve at the dispenser.
- Install appurtenances such as water or air piping in a separate piping trench.
- Ensure vent lines above the ground surface are:
- Constructed with at least schedule 40 steel;
- Protected from traffic;
- Properly anchored; and
- Protected from weather and debris.
- Ensure the vents of a UST system storing a flammable or combustible liquid meet the following conditions:
- If the UST system stores a flammable liquid, the vents terminate 12 feet above the ground surface and 2 feet above an attached building; and
- If the UST system stores a combustible liquid, the vents terminate at least 3 feet above the ground surface.