Trenching and Shoring 29 CFR 1926.650. A Trenching Tragedy. False sense of security Knew they were out of compliance Thought the soil was stable Conditions changed overnight A worker died. Trenching Statistics. About 400 U.S. workers die in trench-related accidents each year
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1. Describe two signs of soil distress:__________________________________________,__________________________________________.
2. Describe why a worker buried up to the neck would not be able to breathe:__________________________________________.
3. When working in a 4-foot trench, there must be an exit within 25 feet. True or False
4. Shielding is designed to prevent an excavated wall from caving in. True or False
5. Name a portable device used for shielding:__________________________________________.
6. How does water or rain impact the classification of soil? ___________________________________
7. Trenches near landfills may not contain enough oxygen to support life. True or False
8. Describe a way to protect trench workers from falling soil or objects:_______________________________
9. Excavations need to be inspected only right after they are first dug. True or False
10. If you don’t know the soil type, what slope angle should you use to be safe?_____________________________
1. Signs of soil distress include cracks, slumping, bulging, sinking edge, or trickling pebbles.
2. The soil exerts about 800 lbs. of pressure on the chest, which prevents expansion.
4. False. Shoring prevent cave-ins and shielding protects workers from a cave-in.
5. A trench box is a portable device that is usedfor shielding.
6. Rain or water decreases the stability of soil. Saturated soil can be very unstable.
7. True. The trench might be filled with a heavy gas (from the landfill) that displaces oxygen.
8. Remove loose soil by scaling, provide protective barriers, keep material 2 feet from trench’s edge.
9. False. Inspect excavations daily, throughout the shift, and after conditions change.
10. 1-1/2 feet horizontal for every vertical foot. So a 10-foot-deep-trench would slope out 15 feet.