Shafts, Pits & Bell-Bottom Holes

A shaft or pit is an excavation that goes down deeper than it is wide. A bell-bottom hole is a drilled pier with a widened base. Workers who enter these have little room to escape, face cave-ins, bad air, falling objects and difficult rescue. Deaths in pits and shafts often involve more than one victim, when co-workers climb in to help and are also overcome.

• Foundation Crews
• Utility & Pipeline Workers
• Underground Contractors

What these excavations are

• Shafts: vertical or steeply inclined excavations used for access to tunnels, pump stations, elevators, utility vaults and deep foundations. Depth is greater than width.
• Pits: excavations for equipment, tanks, valve vaults, pump rooms and basements.
• Drilled shafts and caissons: large-diameter holes for piers and foundations, which may be cased with steel or concrete, or dug with a slurry.
• Bell-bottom pier holes: a drilled hole with a flared bottom, where workers sometimes enter to clean or inspect the bell before concrete is poured. They are especially dangerous.
• Some are covered by OSHA’s excavation rules (29 CFR 1926 Subpart P), and some by the underground construction rules (Subpart S, 1926.800 and following), which cover shafts and caissons, depending on the work. A competent person must determine the right requirements. See Competent & Qualified Persons.

Main hazards

• Cave-ins and wall collapse: deep, narrow cuts concentrate soil pressure. A small slide can bury a worker. See Cave-In Warning Signs.
• Bad air: low oxygen, carbon monoxide from engines, hydrogen sulfide, methane and other gases collect at the bottom and don’t clear without ventilation. Many are confined spaces. See Trench Atmospheres, Confined Spaces and Oxygen-Deficient & Enriched Atmospheres.
• Falling objects and people: tools, soil and equipment dropped from the surface can strike workers below. Workers can fall in at the edge. See Excavation Edge Protection.
• Water and flooding: groundwater and rain can fill a pit quickly, and weaken walls. See Dewatering.
• Difficult access and rescue: ladders in deep shafts are tiring, and it’s hard to lift an injured person out.
• Hoisting hazards: buckets, cranes and hoists moving people and materials, with the risk of dropped loads or rigging failure. See Rigging Basics.
• Electrical hazards: wet conditions, temporary power and buried utilities. See Utility Strikes and GFCI Protection.
• Heat, noise, poor lighting and fatigue.

Planning and protective systems

• Plan the job with a competent person, including soil classification, depth, ground water, nearby loads and structures, utilities, shoring design, hoisting, ventilation and rescue. See Soil Classification and Deep Excavations.
• Call 811 and locate and protect utilities before digging. See Call 811.
• Use a protective system for any entry: shoring, shielding, sloping (where space allows) or, for drilled shafts, steel casing, liners or slurry that keeps the hole stable, designed by a registered professional engineer for depths over 20 feet. See Protective Systems, Hydraulic Shoring and Timber Shoring.
• Bell-bottom holes: workers should not enter an unsupported bell. Entry typically requires a casing or lining through the shaft and engineered support for the bell, with a harness, lifeline and a standby. Many companies prohibit entry and use cameras and remote inspection instead.
• Keep spoil and equipment back from the edge, at least 2 feet or farther as designed. See Surcharge Loads.
• Cover or guard openings when not in use, and fence the area to keep people and animals out. Mark and light the area.
• Control water with pumps or well points, and keep drainage away from the opening.

Air quality and ventilation

• Test the air before entry and continuously while workers are in the hole, for oxygen, flammable gas, carbon monoxide, hydrogen sulfide and other likely gases. See Gas Detectors.
• Ventilate with blowers that draw clean air to the bottom. Keep engines and exhaust away from intake air. Don’t run gas engines in or near the hole. See Carbon Monoxide.
• Use a permit system where the shaft is a permit-required confined space, with an attendant, entry log and rescue. See Manholes & Underground Vaults.
• Provide respiratory protection when ventilation can’t control hazards. See Respiratory Protection.

Access, hoisting and communication

• Provide safe access: ladders, stairs or ramps within 25 feet of workers in trenches 4 feet deep or more, and in shafts follow the applicable rule. For deep shafts, use a hoist or lift designed for people, with proper rigging and inspection. See Access, Egress & Spoil Piles.
• Hoists and buckets: use rated equipment and rigging, inspect before use, and keep workers from under suspended loads. A trained signal person and a reliable communication system are essential.
• Lighting and communication: provide enough light, and a way for workers at the bottom to talk to the surface (radio or phone). Use a standby person at the top for entry.
• Limit entry to those who need to be there, and keep a count.

Rescue planning

• Plan rescue before entry. Know who will perform it, what equipment they have and how long it takes. A harness and retrieval line with a winch or hoist can save time for non-entry rescue.
• Never enter to rescue without proper protection. Many deaths are of would-be rescuers. Call 911 and trained rescuers. See Trench Emergencies and Emergency Action Plans.
• Keep rescue equipment ready at the site, including a stretcher or basket suitable for vertical lifts, and run drills.
• Use first aid trained staff, and know the route for emergency vehicles. See First Aid Basics.

Shaft and pit checklist

• A competent person planned the work, classified the soil and identified the applicable rules
• 811 was called; utilities are located; spoil and equipment are set back from the edge
• A protective system (shoring, shield, casing or liner) is in place, and bell-bottom holes are not entered unsupported
• The air is tested and ventilated; permits and attendants are used where required
• Safe access and rated hoisting, lighting and communication are provided
• A rescue plan with equipment is ready before anyone enters

Last updated: October 5, 2026