Trench box violation

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## Case 24. 18-year-old male carpenter killed when 10-foot excavation wall collapsed burying him. An 18-year old male carpenter was part of a work crew installing a 4-inch sewer line to a new residence. He was working in a trench that was approximately 52 feet long and 10 feet deep. The east wall collapsed approximately midway in the trench, completely covering him. The excavation did not have a trench box, proper sloping or shoring. He was found with his head against the west wall of the excavation. After digging him out of the excavation, emergency personnel transported him to a local hospital where he was declared dead. He died of compression asphyxia and blunt force injuries to his head. MIOSHA issued the following Serious citations to the employer: 1. The employer had an inadequate safety program in place that does not meet the minimum requirements set forth in MIOSHA Construction Safety Standard Part One General Rules. (General Rules, Part 1, Rule 114(1)) 2. The employer did not have any persons at the work place with a valid first aid training certificate, exposing employees to lack of medical procedures to be followed if needed. (General Rules, Part 1, Rule R408.[redacted postal code](3)) 3. The employees were not wearing head protection while installing a sewer line and were exposed to being struck by clumps of heavy damp excavated clay at the edge of the excavation an were also exposed to being struck by the back hoe while working in the swing radius. (Personal Protective Equipment, Part 6, Rule R408.[redacted postal code](1)) 4. A 10-foot deep excavation with vertical sides was not cut consistent with a proper evaluation by a qualified person during the installation of a sewer line. (Excavation, Trenching, and Shoring, Part 9, Rule R408.[redacted postal code](5)) 5. Excavated materials were at the edge of the 10-foot deep excavation, exposing employees installing a sewer line to a cave-in hazard by the added weight of the soil pile. (Excavation, Tr…

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# 19-Year-Old Construction Laborer Crushed in Trench Collapse While Laying Sewage Pipe (cont.) ## CONTRIBUTING FACTORS The investigation identified the following factors that may have contributed to the fatality: • No soil test was performed Spoil pile was too close to the edge of the trench and soil retaining system was not used • Failure to perform scaling the spoil pile to remove unstable rock • The trench box was not high enough for the excavation site • Vibrations from heavy equipment use and a nearby active railway may have destabilized the soil • Previous excavation projects where the trench work was taking place may have destabilized surrounding concrete and soil • No competent person was on the jobsite • No daily inspection of the jobsite was performed • Employer did not provide hazard recognition training ## RECOMMENDATIONS AND DISCUSSIONS Recommendation No. 1: Trench boxes used in excavation projects should have a wall height greater than or equal to the wall height of the surrounding trench.³ A trench box protects employees from exposure to soil collapsing into the trench where work is being performed. The trench box wall measured only 8 feet high, while the trench itself measured 12 feet and 2 inches high. This left 4 feet and 2 inches of ground and concrete exposed, placing the workers below at danger of a partial trench collapse. A properly sized trench box could have helped protect the workers from the hazard. Recommendation No. 2: Pre-job site hazard analysis should be performed before work commences. The spoil pile was placed too close to the edge of the trench, preventing scaling to remove unstable rock. In order to provide sufficient space between the location of the spoil pile and the edge of the trench, it is recommended the spoil pile should have been placed on the parking lot side rather than by the building. The height of the spoil pile may have been too high by the side of the building. Pre-job soil testing and classificati…

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# Trenching and Excavation (cont.) ## Temporary protective structure (cont.) - Trench Boxes are commonly used in open areas that are away from utilities, roadways, and foundations. Trench boxes can be used to protect workers in cases of cave-ins, but not to shore up or support trench walls. They can support trench walls if the space between the box and the trench wall is backfilled with soil and compacted properly. Otherwise, a cave-in or collapse may cause the trench box to tilt or turn over. Workers should not be present in the box when it has to be moved. - Other: In some cases, the trench or excavation walls are made of rock but are not entirely stable. Support the walls by using rock bolts, wire mesh, or a method that provides equivalent support. ## What should NOT be done during an excavation? - Do not enter an unprotected trench deeper than 1.2 metres (4 feet), or as specified in the legislation. - Do not start digging before locating and de-energizing the buried services. - Do not enter a trench before testing the air for hazardous gasses and vapours, or the lack of oxygen. - Do not place the sections of pipes, piles of spoil, unused tools, and timber, and other materials within 1 metre from the trench's edge. - Do not rely on natural freezing to act as a method of soil stabilization. - Do not work under suspended or raised loads and materials. - Do not stand behind a backing vehicle. ## What can be included in a trenching and excavation inspection checklist? The following are some points to consider. Each circumstance will be different, so be sure to adapt the questions to suit your situation. ## Underground or Utility Services - Know the contact numbers? - Located, identified and informed respective parties? - Grounded, isolated, de-energized, or protected from unplanned release? ## Housekeeping Trenching and Excavation CCOHS

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# SERIOUS: EXCAVATION, TRENCHING AND SHORING, CS PART 9, RULE 408.[redacted postal code](2): Before the excavation begins, the design of the protection used shall be set forth by a qualified person who is knowledgeable in the subject area. Employer failed to evaluate soil conditions; select and construct appropriate protective systems for an excavation up to 22 feet deep. Employer engaged in sanitary sewer installation for new home construction. SERIOUS: SIGNALS, SIGNS, TAGS, AND BARRICADES, CS PART 22, RULE 408.[redacted postal code](1): Traffic control devices shall be installed and maintained as prescribed in Part 6 of the 2011 MMUTCD, which is adopted by reference in R 408.[redacted postal code]. Inadequate traffic control implemented, only "No Through Traffic" signs installed. Excavation in right of way on Fairway Drive, vehicular traffic is being permitted to pass the excavation. Employer engaged in sanitary sewer installation for new home construction. WILLFUL SERIOUS: EXCAVATION, TRENCHING AND SHORING, CS PART 9, RULE 408.[redacted postal code](1): The side of an excavation more than 5 feet deep shall be sloped as prescribed in Table 1, unless supported as prescribed in this part. Sides of excavation are not cut to the proper angle of repose, no shoring, no trench box. One excavation 14 ft. 11 in. north to south, and 15 ft. 7 in. east to west, and 15 to 22 ft. deep. West side of the excavation is near vertical. Employer engaged in sanitary sewer installation for new home construction. Soil conditions previously excavated material, blue clay 0.5 to 1.0 TSF and grey clay 1.25 to 1.75 TSF. 2

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# Trenching-Protection ## Explain dangers You risk injury or death if you enter a trench deeper than 1.2 metres (4 feet) that has not been sloped, shored, or protected by a trench box. ## Identify controls ## SLOPING Sloping the walls is one way to keep a trench from collapsing. The angle of the slope depends on soil conditions. • Type 1 and 2 soils: Cut trench walls back at an angle of 1-to-1 or 45°. That's 1 m (3 ft) back for each 1 m up. Walls should be sloped starting at 1.2 m (4 ft) up the wall. - Type 3 soil: Cut walls back at an angle of 1-to-1, but from the bottom of the trench. - Type 4 soil: Slope the walls at 1-to-3. That's 3 m (10 ft) back for every 1 m (3 ft) up from the trench bottom. Type 1 and 2 GOOD SOIL Minimum 1.2m (4 ft.) Maximum Bank Slope Bank Wall Type 3 FAIRLY GOOD SOIL Minimum Bank Slope Type 4 BAD SOIL 3 Minimum Bank Slope ## SHORING Shoring is a system that supports walls to prevent soil movement. It also helps to support underground utilities, roadways, and foundations. The two types of shoring used most commonly are timber and hydraulic. Both consist of posts, wales, struts, and sheathing. One major advantage of hydraulic shoring is that you don't have to enter the trench to install the system. Installation can be done from the top of the trench. Whenever possible, shoring should be installed as excavation proceeds. If there's any delay between digging and shoring, no one should enter the unprotected trench. ## TRENCH BOXES Trench boxes aren't meant to shore up or support trench walls. They're only meant to protect workers in case of a cave-in. The space between the box and the trench wall should be backfilled. Otherwise a cave-in or collapse may cause the trench box to tilt or turn over. It's also easier to enter the box if soil comes right up next to it. Trench boxes are commonly used in open areas away from utilities, roadways, and foundations. If you're in the trench, stay inside the box. ## LADDERS Whether…

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# Tennessee OSHA's Special Emphasis Program on Trenching & Excavation Because trenching and excavation collapse is deadly and often involves multiple victims, Tennessee OSHA has established a special emphasis program to focus attention and resources on these hazards. It is impossible to predict when an excavation or trench will collapse. The sudden collapse of the walls makes escape almost impossible. The only way to prevent collapse is to slope or shore the walls or install a trench shield and follow the TOSHA trenching and excavation standards contained in 29 CFR 1926 Subpart P. Under this special emphasis program, all TOSHA compliance and consultative services personnel will be on the lookout for trenching or excavation work sites. Personal observation, reports of imminent danger, fatality/catastrophe reports, safety and health agency referrals, employee complaints, and media reports are also used to locate trenching and excavation work. Each occurrence is handled with an appropriate intervention by TOSHA. ## Hazards on the Excavation Site Excavation workers are exposed to many hazards, but the chief hazard is cave-in. TOSHA requires that all employees exposed to potential cave-ins be protected by sloping or benching the sides of the excavation, shoring the sides of the excavation, or placing a shield between the sides and the work area. In addition to cave-in hazards, workers must also be protected from adjacent utility lines, exposure to vehicular traffic, falling loads, hazardous atmospheres, and fall hazards. Utility lines such as gas, electrical, sewer, and water must be located and supported prior to placing employees in an excavation. Employees working in, or near, roadways must wear high visibility vests. Workers are not to work beneath suspended loads, and walkways crossing excavations must be equipped with guardrails. Precautions, including atmospheric testing and emergency rescue procedures and equipment, must be taken when workers enter excavat…

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There is no implemented/coordination of the Safety Program and Procedures with employees required to enter excavation while engaged in the repair of water mains. ## SERIOUS: PERSONAL PROTECTIVE EQUIPMENT, PART 6, Rule 622(1): A helmet, as prescribed in R408.[redacted postal code], was not used to protect the employee where a hazard or risk of injury exists from falling or flying objects or particles or from other harmful contacts or exposures): Employees without head protection working around operating excavation equipment and in an excavation that is 8.5 feet below the roadway surface. ## SERIOUS: EXCAVATION, TRENCHING, AND SHORING, PART 9, Rule 933(2): An excavation that an employee was required to enter did not have excavated and other material stored and retained not less than 2 feet from the excavation edge. Employees are entering/working bent over within an excavation that is 7 feet deep (shallow side) with the spoils directly at the edge. Repair work is being done on an existing, leaking water main along the west side of .... Road. WILLFUL/SERIOUS: EXCAVATION, TRENCHING, AND SHORING, PART 9, Rule 941(1): The side of an excavation more than 5 feet deep was not sloped as prescribed in Table 1, unless supported as prescribed in this part. Two employees were cleaning (prior to repair) a damaged “leaking” 6 inch existing water main in an excavation. The excavation was cut along the west side of .... Road. No trench box or shoring system was used. The excavation measured: • 17 feet long, by 5 feet wide (at the top) by 8.5 feet deep • The east side (along Road) was cut vertically (90 degrees) from the edge of the pavement down • The west side was cut to a 78 degree angle • The bottom of the excavation was approximately 4 feet wide - The soil consisted of water saturated backfill/clay One employee re-entered the excavation and received injuries when a 6 feet by 6 feet X 4 feet section of the east side (under .... Road) collapsed onto him. Employe…