Safe Work in Trenches

1. Most trenches are dug to lay pipe, form foundation walls or place concrete footings. It is easy to try to work fast in a trench and get out without taking safety steps. Don’t! Each year, more than 40 construction workers are killed in trenching accidents.

2. A trench is a confined space with many special problems. Most deaths in trenches are from cave-ins. Other risks are falls, electrocution, being struck by falling objects (or a backhoe), and bad air. Bad air can hurt your breathing, help cause a fire, or poison you. Many workers die trying to rescue other workers.

3. OSHA says every contractor must train workers about hazards and how to protect yourself.

4. If a trench will be dug, the contractor must name a competent person. OSHA says a competent person must know the OSHA excavation standards, be trained in soil analysis and protective systems, can identify hazards, and has authority to stop them right away.

5. OSHA has special rules to protect workers in trenches and excavations. You must follow the OSHA rules unless: The trench is in stable rock, is less than 5 feet deep and a competent person finds no reason to expect a cave-in.

6. The contractor must have all utilities marked before digging. The contractor must call utility companies and shut off all electricity, gas, and water pipes in the trench.

7. Do not use a boom near overhead power lines. If you must operate a boom, ask the competent person to make sure power has been cut off and the lines have been grounded.

8. A trench can be in stable rock, or type A, type B, or type C soil.

9. Stable rock and type A soils are the safest. Most soils are type B. Sand and trenches with water are type C soils.

10. Clay can be type A, B, or C soil; it depends on how much water is in the clay. Many cave-ins happen in clay, because people think it looks safe.

11. You will need to use sloping, benching, shoring, or a trench box to prevent injuries or deaths.

12. Keep the spoil pile 2 feet or more from the edge of the trench. Prevent materials, rocks, or soil from falling into the trench; use barriers, if needed. A competent person should test the air as often as needed to make sure it is safe.

13. A competent person must check the soil. This check helps the competent person choose the right worker-protection system.

14. A competent person must inspect a trench or excvation: before every work shift.

15. A competent person must inspect a trench: If bad air is expected such as, the trench is in a sewer or near a dump or stored chemicals

16. If bad air is expected, OSHA says there must be a rescue plan and rescue equipment on the job site. Rescue teams must have special training. The best way is to follow OSHA rules for rescues from confined spaces. OSHA says the air must have 19.5 to 23.5% oxygen. OSHA says substances that can burn or explode — like gasoline or methane — should be at less than 20% of the lower explosive limit (or lower flammability limit).

17. If bad air is expected, a competent person must test the air: OSHA says substances that can burn or explode, like gasoline or methane — should be at less than 20% of the lower explosive limit (or lower flammability limit).

18. Check the air for toxics like chlorine, carbon monoxide, sewer gases, and hydrogen sulfide. These toxics can kill. Carbon monoxide has no smell. Hydrogen sulfide smells like rotten eggs. The competent person will decide if blowers can keep the air safe.

19. A competent person must inspect a trench: After anything that can increase hazards, such as: Every rainstorm. Vibration (such as, from a passing truck or train).

20. A competent person must inspect a trench: if the trench wall moves, causing cracking, scaling, or bulging. Or a heavy load near the trench moves or gets heavier.

21. Make sure all equipment is in good condition. This includes ladder, water pumps and ventilators.

22. You must have a way to get out, like a ladder within 25 feet of you (if the trench is 4 feet deep or more).

23. Water in a trench means workers are in danger.

24. IF A TRENCH CAVES IN: Get out of the trench. Call 911 (or emergency services). Help your co-workers from outside the trench, if you can. Never go into a trench that is caving in or has bad air — even to rescue co-workers. You can be killed.

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