Solution Summary: Trench Boxes
Trench boxes are designed to protect workers from cave-ins when work must be completed below the earth’s surface.
Description:
Trench boxes, along with techniques such as sloping, shoring, and benching, use engineering controls to create safer in-ground working environments. Trench boxes are lowered into trenches and use fixed solid walls made from heavy-duty metal to protect workers from cave-ins while work is performed below ground level. With a protected work environment, tasks can be completed more confidently and efficiently as less time and energy will be spent worrying about trench structure failure.
Excavations must be inspected by a competent person and cave-in protection, such as trench boxes, must be used when there is a potential for a cave-in or a trench is greater than five feet deep. Using trench boxes protects workers from cave-ins and reduces the risk of injury or death. Working in trenches with unprotected walls as much as five feet below ground surface may be allowed if in stable rock or if determined by a competent person to not pose a risk of cave-ins. The competent person may still recommend use of trench boxes for some soil and work conditions, even though the trench is not greater than 5 feet deep. If soil slopes towards the trench, the box must extend at least 18 inches above the trench surface. Protection for trenches that are 20 or more feet deep must be designed or approved by a registered professional engineer. The excavation may extend two feet below the trench box if the box is designed to handle the force and weight of the soil for the entire depth of the trench. Even with trench boxes in place, workers still need to be observant of their surroundings and exit any trenches that they believe to be unstable until the problem is corrected.
Efficiency Production Trench Shields
| Model | XLSM3 | XLDM | HT6 | HT8 | HT10 |
| Weight (pounds) | 1,450 – 4,080 | 1,460 – 6,082 | 4,090 – 17,630 | 6,150 – 20,570 | 9,180 – 25,940 |
| Height (feet) | 4, 6, or 8 | 4, 6, or 8 | 4, 6, 8, or 10 | 4, 6, 8, or 10 | 4, 6, 8, or 10 |
| Length (feet) | 8, 10, 12, 14, or 16 | 6, 8, 10, 12, 14, or 16 | 8, 12, 14, 16, 18, 20, 22, 24, 26, or 27 | 14, 16, 18, 20, 22, 24, 27, or 30 | 20, 24, 27, 30, or 32 |
| Wall Thickness | 3 inches, single wall | 4 inches, double wall | 6 inches, double wall | 8 inches, double wall | 10 inches, double wall |
| Pipe Clearance (inches) | 22 or 36 | 22 or 36 | 22, 41, 64, or 85 | 22, 41, 64, or 85 | 22, 41, 65, or 85 |
| Shield Rating (pounds per square foot) | 360 – 960 | 840 – 2,400 | 780 – 2,880 | 840 – 2,640 | 840 – 2,820 |
Trench Shoring Company Trench Boxes
| Model | TS 3 inch | TS 4 inch | TS 6 inch | TS 8 inch |
| Weight (pounds) | 1,671 – 4,518 | 3,950 – 12,949 | 6,859 – 20,400 | 11,920 – 29,008 |
| Height (feet) | 4, 6, or 8 | 4, 6, 8, or 10 | 4, 6, 8, or 10 | 4, 6, 8, or 10 |
| Length (feet) | 6, 8, or 10 | 14, 16 or 20 | 20 or 24 | 24, 28, or 32 |
| Wall Thickness (inches, single wall) | 3-3/8 | 4-3/8 | 6-½ | 8 |
| Shield Rating (pounds per square foot) | 954 – 1,800 | 808 – 1,415 | 770 – 1,340 | 994 – 1,340 |
Trench Shoring Services Trench Boxes
| Model | 8 Foot Box | 10 Foot Box | 12 Foot Box |
| Weight (pounds) | 1,550 – 19,500 | 6,390 – 17,350 | 1,550 – 24,950 |
| Height (feet) | 8 | 10 | 12 |
| Length (feet) | 4, 6, 8, 10, 12, 16, 20, 24, or 28 | 16, 20, 24, or 28 | 6, 16, 20, 24, or 28 |
| Shield Rating (pounds per square foot) | 440 – 1,300 | 440 – 1,200 | 440 – 1,300 |
- Wall Thickness: single and double wall options available
Pro-Tec Trench Shields
| Model | Pro 4 Series | Pro 6 Series | Pro 8 Series | Pro HD Series |
| Weight (pounds) | 2,920 – 11,820 | 4,650 – 15,000 | 6,250 – 18,070 | 13,100 – 18,007 |
| Height (feet) | 4, 6, 8, or 10 | 4, 6, 8, or 10 | 4, 6, 8, or 10 | 8 or 10 |
| Length (feet) | 10, 12,16, 20, or 24 | 16, 20, 24, 26, or 28 | 16, 20, 24, 28, or 30 | 16, 20, 24, 28, 30 or 32 |
Wall Thickness (inches, double wall) | 4 | 6 | 8 | 6 or 8 |
| Shield Rating (pounds per square foot) | 775 – 3,000 | 769 – 2,500 | 200 – 2,520 | 1,058 – 2,396 |
Risks Addressed:
An excavation is a man-made cavity in the ground and a trench is an excavation that is deeper than it is wide. Working in trenches increases the risk of injury and death and a significant number of worker injuries and fatalities are directly related to trench cave-ins. Many factors must be considered when the creation of a trench begins, including soil type, amount of moisture present, effect of vibration from equipment and nearby traffic, surcharge load (i.e. excessive weight that can put pressure on the walls of the trench), previous excavation, and weather for the area. Many methods may be used to protect against cave-ins, including the use of trench boxes. Trench boxes protect workers from cave-ins and create a safer work environment (Trenching Safety, 2010).
According to NIOSH, Bureau of Labor Statistics data from 2000 to 2009 indicate that an average of 35 workers per year died in trenching or excavation cave-ins in the United States (NIOSH, 2011). The NIOSH report also noted a study based on an analysis of OSHA data from 1997−2001 that showed 64 percent of fatalities in trenches occurred at depths of less than 10 feet (Arboleda and Abraham 2004). Another study that used OSHA inspection data showed that lack of a protective system was the leading cause of trench-related fatalities (Deatherage et al. 2004).
OSHA has focused heavily on excavation and trenching operations over the past decade. Such operations can be dangerous past four feet deep with cave-ins causing serious injury or death. More serious incidents are likely to occur when work is performed at a depth of six to nine feet. With the average cubic yard of dirt weighing approximately one ton, a person will likely not be able to breathe due to the pressure of the dirt on his or her chest. Even if a person maintains the ability to breathe during a cave-in, it is not guaranteed that the victim will survive injuries from compression of the lungs and other organs. OSHA reviewed cases from 2004 and found they had issued over $7 million in penalties for accidents that most likely could have been avoided (Griffin, 2005).
How Risks are Reduced:
Trench boxes are lowered into trenches to protect workers from cave-ins. Two large, typically steel, plates make up the walls of the trench box. The walls of the box are fixed and positioned to be parallel to the walls of the trench. Horizontal bars cross the structure to keep the two wall plates from compressing. The box sits along the bottom of the trench bed, while the upper edges rise above the trench opening. The walls of the box will stop dirt from collapsing on workers if the trench begins to cave in. To ensure optimal safety, the trench box is pulled through the trench as work advances (Texas A&M University, 1992).
Even with trench boxes in place, workers still need to be observant of the surroundings and exit any trenches that do not seem stable until the problem is corrected.
While there are no peer-reviewed data on these specific controls, manufacturers’ testing indicates accidents can be significantly reduced through the proper use of trench boxes. The extent of the reduction is dependent on the type of work being performed, the depth and width of the trench, the soil composition, and the trench box being used.
Trench boxes create a safer work environment by protecting workers from cave-ins. Without the use of a trench box the probability of worker injury due to trench collapse rises. Trench boxes help protect workers by preventing collapsing trench walls from reaching workers while they perform tasks on underground utilities, roadways and foundations. Work can therefore be safely accomplished below grade level (OSHA Technical Manual, 1999).
Effects on Productivity:
Trench box use has helped to reduce the number of injuries and fatalities in trench work areas. Trench boxes help to protect workers from cave-ins and provide a safer work environment. Avoiding injuries from cave-ins ensures production will not be disrupted by a potentially catastrophic event that can significantly damage a company. A safer work climate greatly improves company morale, reduces absenteeism and ensures company viability.
Contributors:
Andrew Kingston and Michael R. Cooper - Aria Environmental, Inc.
Bruce Lippy - CPWR
Availability
NIOSH Workplace Solutions Sheet
The National Institute of Safety and Health (NIOSH) has published a series of “Workplace Solutions”, which are easy-to-understand recommendations from NIOSH research results. Related to this Construction Solution, please find more information on:
Preventing Worker Deaths from Trench Cave-ins
Pro-Tec Trench Shields
To obtain information, visit http://www.pro-tecequipment.com
or contact 1-800- 292-1225
Efficiency Production Trench Shields
To obtain information, visit http://www.efficiencyproductihttp://www.efficiencyproduction.com
or contact 1-800-552-8800
Trench Shoring Company Trench Boxes
To obtain information, visit http://www.trenchshoring.com
or contact 1-800-423-4411
Trench Shoring Services Trench Boxes
To obtain information, visit http://shoring.com
or contact 1-800-746-7464
