Before digging, verify locations of existing pipes. Know where gas, water, power, sewer, or other existing lines are. Puncturing lines can create other hazards not initially expected. Designate a competent person for the jobsite.
Have a competent person verify the type of soil on site. The following is a general classification of the soil. Each soil type determines the mandated slope and dimensions for digging a trench.
|Soil Classification||Soil Types|
|Stable Rock||Natural solid material|
|A||Clay, silty clay, sandy clay, and clay loam|
|B||Angular gravel, silt, silt loam, and sandy clay loam|
|C||Gravel, sand, and loamy sand|
The following are the guidelines for sloping according to soil type:
|Soil Classification||Maximum Allowable Slopes- Height:Vertical|
|Stable Rock||Vertical (90Щ)|
|A||3/4:1 or 53м/span>|
|B||1:1 or 45м/span>|
|C||1 1/2:1 or 34м/span>|
When selecting to shore trenches, be certain that all needed equipment is present. Do not attempt to assemble and place shoring without all the appropriate components. Inspect all the shoring pieces and verify the integrity of the shores. Do not use shores as a means of ingress or egress; doing so can weaken the integrity of the shores. Install first from the top and then the bottom. Upon removal, bottom pieces should be removed first. Watch for pinch points that may exist on the shoring or shield protection.
Place boxes in trench where work is to be done. Do not ever work outside the trench box. As your work progresses in the trench, move the trench box to protect workers in the area where work is being done. Do not move trench box while employees are inside the trench area.
Ingress and Egress
A worker should have an access/egress within 25 feet of their workspace. When the trench is more than four feet deep, a 25-foot access way is mandatory.
Check the air quality within the trench daily. Test for oxygen levels, toxic gases, and hazardous fumes. Do not allow running motor vehicles near the opening of a trench.
Water can weaken the soil and cause a possible cave-in. Understand the water table and where water levels may rise. In some cases, water will need to be pumped out of the trench while employees are working.
Do not place spoils within two feet of the edge. It poses the potential of falling back in and burying a worker. Also, the added weight may compromise the strength of the trench wall.
Tools and Equipment
If tools that cause vibration are used, ensure that they will not weaken the walls of the trench. Keep all tools and equipment at least two feet away from the edge of the trench opening. Remind employees that vibration of equipment may affect the stability of trench walls.
NOTICE: This guide may make reference to the Occupational Safety and Health Administration (OSHA) regulations; however the guide is not legal advice as to compliance with OSHA or other safety laws, codes, or regulations. Compliance with OSHA and other safety laws codes or regulations, and maintaining a safe work environment for your employees remains your responsibility. WCF Insurance does not undertake to perform the duty of any person to provide for the health or safety of your employees. WCF Insurance does not warrant that your workplace is safe or healthful, or that it complies with any laws, regulations, codes, or standards.