151.1. When more than 10 tires or more than 2,000 kg (4,409 lb) of other combustible materials, such as conveyor belts or ventilation ducts, are stored underground in the same location, the tires or materials must be stored in a depot or enclosure that(1) is identified;
(2) has a fire hose or fire extinguishing system; and
(3) is located at least 15 m (49.2 ft) from any place where welding or cutting work is carried out.
In addition, no person may park an unsupervised motorized vehicle less than 15 m (49.2 ft) from a depot or enclosure referred to in the first paragraph or carry out repair or maintenance work inside the depot or enclosure.