Risk Management Department

1. Risk Management Department Excavation Safety May, 2008

2. Excavation Safety Introduction In order to prevent injuries and improve work productivity, APS has developed this training to provide you the knowledge to stay safe when working in and around excavations.

3. Excavation Safety Introduction • About 400 U.S. workers die in trench-related accidents each year • About 6,400 are seriously injured For this reason it is important to understand how to stay safe in and around excavations

4. Excavation Safety Introduction In this training we will cover: • What is a trench? • Soil characteristics • Collapse types • Shoring techniques • Safety requirements

5. Excavation Safety What is a Trench? • A narrow excavationthat is deeper than it is wide • No more than 15 feet wide at bottom • Walls will eventually fail

6. Excavation Safety What is a Trench? Failure of trench walls results in cave-in: • Soil or rock that suddenly falls or slides into an excavation • Sufficient quantity to entrap, bury, injure, or immobilize • Soil gravitates downward, pressure pushes soil inward toward the trench • Bottom third of wall typically fails first • Soil above the collapsed lower wall follows

7. Excavation Safety What is a Trench? Cave-ins are dangerous to workers: • Soil weighs 125 lbs. per cubic foot • A worker can be crushed by soil, rock, or an object • Suffocation—even if worker’s head is not buried, soil prevents chest expansion • Worker becomes immobilized by soil’s suction effect

8. Excavation Safety Soil Characteristics • Type A (most stable) — dense and heavy clay • Type B — silt, sandy loam, medium clay • Type C (least stable) — gravel, loamy sand, soft clay

9. Excavation Safety Soil Characteristics Factors affecting soil strength: • Water • Vibrations • Erosion and Weathering • Excavation Depth • Slope Steepness • Degree of Soil Compaction

10. Excavation Safety Soil Characteristics Signs of impending collapse: • Fissures or cracks on excavation face • Slumping of material from excavation face • Bulging or heaving of material at the bottom of excavation wall • Sinking of excavation’s edge • Ravelling, or small amounts of material (e.g., pebbles) trickling into excavation

11. Excavation Safety Collapse Types There are four types of trench collapses: Spoil Pile Slide Side Wall Shear Slough–in Rotation

12. Excavation Safety Collapse Types Spoil Pile Slide - Collapse of material that has been removed from the trench back into the trench

13. Excavation Safety Collapse Types Side Wall Shear - Collapse of side wall from the top into trench

14. Excavation Safety Collapse Types Slough-in - Collapse of side wall from middle of wall

15. Excavation Safety Collapse Types Rotation - Collapse of bottom third of trench wall causing secondary wall collapse

16. Excavation Safety Shoring Techniques Engineers are often required to design shoring, which is a construction procedure used specifically to maintain the stability of the walls of an excavation and provide protection to workers who may enter the excavation

17. Excavation Safety Shoring Techniques To mitigate the danger of cave-ins, there are 4 main techniques to shore trench walls: Wood Support Screw Jacks Hydraulic Shores Trench Cages

18. Excavation Safety Shoring Techniques Wood Support

19. Excavation Safety Shoring Techniques Screw Jacks

20. Excavation Safety Shoring Techniques Hydraulic Shores

21. Excavation Safety Shoring Techniques Trench Cages

22. Excavation Safety Safety Requirements At least one worker in each work crew must be experienced in the type of work being performed in excavations At least one worker should be trained in first aid

23. Excavation Safety Safety Requirements Protecting the area around the excavation: • All work areas must be adequately guarded or barricaded by fences, guardrails or a covering sufficient to prevent persons from falling into the excavation • Excavations might endanger stability of buildings, walls, other structures • Sidewalks, pavement not undermined unless supported to prevent collapse on excavation workers

24. Excavation Safety Safety Requirements Protecting workers in excavations: • Protect workers from loose rock/soil that may fall from an excavation face • Use scaling to remove loose soil • Use protective barricades, such as shoring or shields • Protect workers from material or equipment that could fall into the excavation • Keep material/equipment at least 3 feet from edge • Use retaining devices

25. Excavation Safety Safety Requirements Protecting workers in excavations: • Excavation sites cannot be covered with anything such as piles of excavated material or excavation equipment which might accidentally fall into the excavation

26. Excavation Safety Safety Requirements Protecting workers in excavations: • Trenches 4 feet deep or more must have exit means within 25 feet of every worker • Use fall protection • Do not work on sides of sloped or benched excavation above other workers • For parallel construction have a worker on top to watch excavation walls to warn trench workers of potential hazards

27. Excavation Safety You are finished! You have finished the Excavation Safety training. Download the quiz from the Risk Management website’s training page. Print the form and be sure to write your name, location and employee number in the spaces provided. Complete the ten questions and have your supervisor send it to the Risk Management office