On June 19th through 24th, the National Utility Contractors Association (NUCA) will be sponsoring a Trench Safety Stand-Down to raise awareness and prevent accidents in excavation work. One of the major ideas behind a safety stand-down is to increase awareness and focus on safety by encouraging participants to stop, think about safety, and determine ways to work more safely and effectively. Awareness is the first step toward changing behavior. Becoming aware is a thought process that must focus on the subject at hand. When dealing with excavation safety, this process begins by examining what has gone wrong before, both internally and within the industry, as well as what can potentially go wrong. Once a set of hazards has been identified, a safe mitigation plan can be developed. I have been fortunate to have been involved in the excavation industry for over 25 years and I’d like to pass along some of the things that I’ve learned that may assist those preparing to participate in the NUCA Trench Safety Stand-Down or as part of recurring safety meetings that a crew may host.
Shoring System Job Hazard Analysis
At the NUCA website in its suggestions for preparing a successful trench safety stand down the organization asks and states:
What types of incidents could happen?
- Cave-ins
- Struck-by
- Trips and falls
- Materials handling
- Other
This list is essentially the start of a Job Hazard Analysis (JHA). A JHA is a technique that focuses on job tasks as a way to identify hazards before they occur. It focuses on the relationship between the worker, the task, the tools, and the work environment. In this article, I would like to focus on the task and the tools part of the analysis as it relates to excavation shoring equipment.
Excavation planning and shoring systems save lives, however, there are hazards associated with the shoring installation process. Shoring systems present unique hazards that must be thoughtfully considered. They are constructed from heavy steel and aluminum elements that have to be assembled and lifted in place. Means and methods have to be developed depending on the soil types to get them safely into and out of the ground.
When we ask the question, “what type of accidents occur when shoring is being used?” and or ”what hazards are present?”, we find that the type of incidents and hazards that occur include the following:
- Loading and handling shoring equipment
- lack of appropriate and capacity rated rigging equipment
- improper stacking of hydraulic shores, steel plates, etc. results in “card deck” spills
- not slinging and lifting from properly designed lift points can cause equipment to break apart and fall during lifting and placing operations
- Assembling shoring equipment like hydraulic shores, shoring shields, and buildable boxes
- improper lifting and stabilizing equipment
- lack of enough hands to stabilize the equipment and insert necessary pins
- hand, head, and eye injuries from pounding and prying
- Inserting into the excavation
- tag line and swinging issue
- workers maneuvering around open excavation without handrail and barricading
- workers maneuvering lifted equipment around handrail and barricading
- cave-ins while setting equipment in unshored holes
- unobservable undermined paving
- setting stacked trench shields without sufficient rigging to stack more than one box at a time
- with hydraulic shores, pinched and severed fingers during rigging and setting
- workers in an unshored excavation installing shoring
- worker lifting injuries
- During the excavation process
- no fall protection above the shoring
- falls during entering and exiting
- workers exiting from the shored area into the unshored trench
- objects falling or being kicked into the excavation from above
- caught-between production work materials being lifted into the excavation and shoring system
- unstable, slippery, muddy, soft, employee work base at the bottom of the excavation
- insufficient workspace between production work and shoring walls.
- formwork construction, hand digging, pry baring, sling removal access require a certain amount of space to properly and safely use the tools.
- Shoring removal
- cave-in at time of hydraulics release
- with stacked shoring shields, worker entry into the unshored area after the top shield is removed (slide-rail systems are specifically designed to be removed from the bottom up)
- broken shackles and lift cables due to excessive force used to free up embedded shoring
- broken and dismembered shoring equipment falling apart in the air while being lifted out
- a repeat of item 3 hazards
This is, of course, just a partial list of hazards associated with shoring equipment. Anyone that has experience working with shorings systems could probably double the size of this list. This list can be a start to the “Job Hazard Analysis“ for shoring systems and can be extended further by looking at individual types of shoring systems, timber, hydraulic shoring, shoring shields, aluminum buildable boxes, sheeting and bracing, and other systems as well as combinations of these systems. These lists are by nature overview and broad as it’s difficult to identify every possible hazard, or accident associated with each type of shoring system because the surrounding conditions are unique to every project and change on a daily basis. This adds a layer of hazards that can only be identified at the site at the time of the work and reinforces the need for the Competent Person to routinely inspect the job to look for and prevent these hazards.
A JHA should be conducted prior to the start of every one of these operations, 1 through 5, as well as JHA’s for general operations, such as working around heavy equipment, pipelaying operations, concrete forming, and placing, etc. Every item should be discussed with the crew and a complete mitigation plan should be developed for every identifiable hazard. For instance:
Item 1 bullet 3 – not slinging and lifting from properly designed lift points would lead to…
- a rule not allowing any equipment on the job site that does not have properly designed lifting attachments
- inspecting lift attachments before and after use
- making sure rigging shackles and equipment on hand fit the lift point and will not bend, bind or break the lifting attachment
- determining weights of equipment being lifted and making sure the rigging system has adequate capacity
Through this process, it is entirely possible to mitigate every hazard on the job and have zero accidents. In one way or another OSHA Construction Regulations require it to be done.
The Worker and his Knowledge Base
When dealing with shoring equipment installation there are some safety measures that a contractor must complete prior to getting the shoring operation underway. This is the part of JHA that focuses on the worker and his environment.
Under OSHA Subpart P Excavations there are several requirements that call for a competent person to perform safety activities. The shoring manufacturers, suppliers, and site-specific shoring design engineers have taken this a step further. They are working towards incorporating the following requirement into tabulated data and site-specific shoring plans that read:
The contractor must have a competent person that is:
- Instructed in the use of the shoring system being installed
- Trained in the use of the shoring system being installed
- Experienced in the use of the shoring system being installed
In addition, the person should be present at all times during the installation and use of the shoring system.
This requirement is designed to ensure that there are workers on the job with sufficient knowledge of the subject at hand to identify and mitigate hazards in shoring system applications.
Instruction consists of reading and understanding the tabulated data including installation and removal procedures. A job hazard analysis related to the specific equipment should be part of the instructions, (this is not a substitute for the JHA that has to be conducted at the site prior to installing the shoring). Training means actually installing and handling the shoring equipment under the direction of an instructor, and experience means installing and working in the field under the direction of a person that has had knowledge of several similar installations. If the contractor does not have a person on his crew with the requisite experience, the contractor should seek out that experience. The analogy to this is an apprenticeship, where a person would undergo classroom or book learning on his trade and then work for some period of time under another person that has mastered the trade before he/she can be considered a master tradesman. The partial list of hazards, at the first of this article, gives an indication of the number of potential problems that can arise with shoring system use and emphasizes how important it is to have a complete understanding of the safety issues associated with this work.
Resources Available
National Trench Safety is dedicated to serving the underground construction industry. Every step of the way we have tools that a contractor may utilize to help develop a safe, cost-effective shoring application. Our services designed to support customers include:
- OSHA compliant training classes offered at NTS branches or a customer’s job site or office
- NTS Mobile App which features
- the entire OSHA Subpart P Excavations regulation
- information and selection criteria for all types of shoring applications
- tabulated data
- installation and removal training videos for most excavation protection systems
- Site-specific engineering services, including consultation at pre-bid time, planning services at post bid time, and site-specific shoring plans stamped in all states and Canada
For field job site hazard analysis and solutions:
- The NTS Mobile App, which is conveniently accessible in the field by phone or tablet, provides key information including tab data, shoring plan, OSHA regulations, and products that will help mitigate the additional hazards identified in the JHA
- In addition to shoring equipment, NTS provides a variety of safety equipment that adapts to the shoring system, such as ladder access platforms, davit arm, lightweight portable bridges for trench crossing, and access to shoring systems, and handrail systems that adapt to shields, slide rails, build-a-boxes, and sheet pile.
- Engineering staff available to you at any time.
Safe means, methods, and mechanisms for every trench excavation can be developed. It starts with awareness and analysis of the situation and follows up with a properly executed trench safety plan. No matter how much time or cost is involved, it is always less expensive than the mental and physical cost of an accident.
About the Author: Joe Turner, P.E. serves as National Trench Safety’s Director of Engineering, Research, and Product Development. Mr. Turner is one of the most recognized figures in the trench safety industry, having provided trench safety plans for the last 20 years. Among his many accomplishments, is the book Excavation Systems, Design, Planning and Safety, which was published by McGraw-Hill in 2008 and is still used today as a reference for many students and professionals regarding proper engineering techniques.
DISCLAIMER: the information contained in this article is provided for general and illustrative purposes only and is not to be considered Site Specific and or designated engineering for any project or work zone, nor is it to be used or consider to be tabulated data, technical data, advice and or counsel to be used on any job site. Each project is different and is the responsibility of the employer’s designated Competent Person to make decisions upon what systems and methods may be used in compliance with the federal and local regulations, manufactures tabulated data, engineered drawings, and other plans.