Chapter 1: General Safety
The explosives industry proclaims safety is of paramount importance to protect people, property, and the environment. Blasting activities present risks to blasters-in-charge and their crews different than those found in the work environments in many other industries. Handling energetic materials exposes people, property and the environment to hazards that can result in catastrophic events. Unfortunately, comprehensive injury and fatality data for all blasting industries is not currently, uniformly and centrally collected. This chapter is a general discussion of safety as related to the blasting operation. Safety is not considered to be an independent issue, but inherent in all blasting processes and activities. Specific safety discussions are located in other chapters in this book.
The good news concerning blasting safety in the U.S. mining industry is that the rate of injuries and fatalities has steadily dropped over the past 2 to 3 decades as reported by the U.S. Mine Safety and Health Administration (MSHA) in Figure 1.1 and Table 1.1. This can be directly attributed to the development of less sensitive explosives and more versatile initiation systems with features that reduce some of the hazards of premature detonation; the fact that the personnel using explosives are better trained and qualified; and the creation of more comprehensive explosives security programs.
Figure 1.1 Trends in blasting accidents. (Source: Reprinted by permission of MSHA)
However, the bad news is that blasting accidents still occur, and nearly all of them could be prevented. Blasters must be aware and accept that extraordinary care is required in their occupation. However, human nature being what it is, complacency finds its way into the work habits, attitudes, and behaviors of the individual and the crew. Blasting accidents are rarely due to unexplainable
Modern explosives are the safest and most reliable ever produced, but they still require good judgment of all who store, transport, handle, and use them.
Table 1.1 Annual U.S. mining blasting accident averages. (Source: Reprinted by permission of MSHA)
Who Is Responsible?
Ultimately the knowledge, skills, attitudes and behaviors of individuals create either a safe and productive work environment or an unsafe one. Co-worker and peer pressure can be useful to improve safe work behavior. Sometimes the attitudes of co-workers are not positive influences with regard to safety. People must often work alone or unsupervised completing tasks such as making a primer or stemming a borehole. This requires that they (1) be self-reliant, (2) be self-accountable, (3) believe in the necessity for working in a safe manner, and (4) understand the potential consequences of their actions or omissions. When repetition builds work habits, it is important that it results in the development of safe habits. However, the overall safety of an operation is only as good as the safe processes used by every individual involved. In short, safety is a team effort and everyone has a very important responsibility.
Corporate Responsibility
Company management must be firmly committed to safety, and willing to furnish the resources in personnel, equipment and training necessary to create safe operating procedures and conditions. While various federal and state regulations mandate basic safety requirements, all companies should have their own safety policies that clearly spell out the practices to make sure the explosives are handled and used safely on their specific types of operations.
Regulatory agencies and most company policies normally designate a single individual as the "blaster-in-charge", i.e., the person responsible for all blasting activities including safety on a blast site. While it may be reasonable to expect this blaster-in-charge to direct and monitor all blast related conduct to ensure a safe workplace, it is unreasonable to expect that the burden of a safe operation rests entirely on him or her alone. A safe blasting operation depends on the work habits, attitudes and cooperation of everyone in the company from the laborer stemming the boreholes to the CEO.
Blaster-In-Charge Responsibility
If the blasting operation is to be under the control and supervision of a single blaster-in-charge, then that person must be given the authority to make all decisions and take the needed actions to ensure that the blasting is always done in a safe manner. The blaster-in-charge must be capable by means of training and experience to recognize hazards specific to his job site, and be able to incorporate applicable safety statutes and procedures that will eliminate all recognized hazards. The blaster-in-charge has the ultimate responsibility for the safety and well-being of everyone who could be affected by his blasting.
Although specific safety issues will be dealt with in other chapters of this book, the following are some general areas where a blaster-in-charge must plan for and control the hazards that may arise. The measures that he or she takes affect the safety in several areas. The blaster-in-charge must (1) ensure the security of the explosive materials, (2) ensure the safety of everyone working at the site, and (3) take every precaution to protect the general public living and working in the vicinity of the blast area.
Safety at the Blast Site and Beyond the Blast Area
Safety goes beyond simply using the industry safety best practices for handling and using explosives. A good and responsible safety program provides for the safety of (1) all people handling explosives at the blast site, (2) all people working near the blast site, and (3) the general public living beyond the blast area. This comprehensive view of blasting safety addresses the following seven processes and activities of (1) planning and design, (2) transportation, (3) storage, (4) on-site procedures, (5) loading the blast, (6) initiating the blast, and (7) post blast inspection.
Planning and Design
Well-prepared blast plans improve productivity and make for a much safer work environment. Blast plans address safety issues before the work commences. They address work factors such as (1) the number of and skill requirements for the drillers and blasting crew assigned to the project, (2) special tools or equipment required due to job conditions, and (3) a work schedule that provides adequate time to meet production deadlines and the flexibility to handle unforeseen delays. Haste is always detrimental to both the quality and safety of work.
Before delivering explosives to the blast site, the blaster-in-charge must survey the area to identify all existing hazards such as (1) evidence of any underground utilities that may be affected, (2) identification of unusual geological conditions that mandate extra caution, including the rock to be broken and unstable bighwalls or natural cliffs in the area, (3) sources of stray electricity, like flames, or radio frequency (RF) energy, (4) entry points to the job site, and (5) the methods expected to control access.
The blaster must prioritize safety considerations over production goals. It is not unusual that these two elements conflict. For example, the blaster might limit flyrock with smaller blasts that can be made, or additional stemming that may reduce fragmentation. All blast designs must comply with sound safety principles, and must always be completed before any loading is started. The blaster's choices of borehole diameter, depth, stemming, and powder factor must all be appropriate for the rock type, its structure, and the blast size and confinement that must be controlled. Chapter 10 discusses blasting safety program elements in more detail.
The blaster-in-charge must ensure that all explosives required for the blast design are available. This requires planning and prevents the situation of having to make do with what's on hand. Anytime a different explosive material or initiation system is first used, it is essential that the blaster be thoroughly familiar with its guidelines for use and its limitations. A failure to properly understand the use of a new product is an unsafe condition. The blaster-in-charge must also communicate the necessary product use information to the crew in a manner that ensures no mistakes.
In addition, the blaster-in-charge must have a clear idea of what to do in the event of an emergency. This means having a list of all emergency responders and their telephone numbers. This list must be posted so that it is available to all on the job site. Any trained first aid providers and first aid kits that are available should be known.
Transportation
Always transport explosives in compliance with all laws and regulations governing this activity. These regulations are detailed and stringent in an effort to ensure that the explosives materials move in a safe and secure manner. All vehicles transporting explosives must be well maintained and have all necessary safety equipment such as fire extinguishers. They must display adequate warning signs and placards. Never place other materials in the same cargo space with the explosives, and never leave a vehicle containing explosives unattended.
Storage
When storage of explosives is required on the job or mine site, the blaster must ensure that the materials are stored in compliance with the laws and regulations in that jurisdiction. In the United States, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) enforces the U.S. federal laws and regulations concerning the construction, location, contents and security requirements of storage magazines. U.S. federal laws and regulations prescribe minimum explosives storage standards. Although all storage sites must comply with these standards in the U.S., compliance with more rigorous local standards is always necessary.
Blast Site Procedures
Sound on-site procedures ensure (1) all workers have the necessary personal protective equipment (e.g. hard hat, hard toe boots, eye protection, ear protection, and specialized devices as the blasting environment requires) and (2) all tools, testing equipment, and measuring devices are in good condition and readily available. The blaster-in-charge conducts "tailgate" meetings to ensure everyone in the blasting crew (1) knows their job responsibilities, (2) is familiar with all hazards on the site and knows how to deal with them, and (3) is knowledgeable about the necessary equipment on site.
The blaster-in-charge must use tapes or other measuring devices to lay out the blast pattern. It is unprofessional to lay out boreholes by pacing or estimating. Measuring tools ensure patterns have accurate borehole locations. After the boreholes are drilled and before loading begins, check boreholes for correct depth and for potential obstructions that could affect loading. If any borehole must be re-drilled, then re-drill them before any explosives are brought to the blast site.
The blaster-in-charge must ensure the distribution of crushed stone for stemming on the blast site prior to the commencement of loading. And make every effort to keep vehicles and mobile equipment off the blast site once the loading commences. The blaster-in-charge must protect the blast site by (1) flagging, (2) barricading and (3) demarcating the blast site clearly to prevent unauthorized persons or equipment from coming on to the site once loading commences.
Loading the Blast
If the routine practice is to lay out detonators next to the boreholes to facilitate loading the delay pattern, then keep the detonators separated from high explosive cartridges or boosters until the time of loading each borehole. The blaster-in-charge must ensure all personnel follow the Basic Loading Safety Rule is followed.
Basic Loading Safety Rule
Once the detonator is inserted into the high explosive (booster) to form the primer, immediately load it into the borehole.
The blaster-in-charge must be careful when using tamping or loading poles on the primer cartridge carefully ensuring never to damage the down hole tubing or wires. Continuously monitoring explosives column when loading ensures there are no charge separation or incorrect amounts of explosive accidentally loaded into the borehole.
The blaster-in-charge must always use systematic methods to hookup or connect the initiation system and be vigilant to observe other members of the blast crew who are designated to assist with this task are doing so correctly. When using electric initiation systems the blaster-in-charge must check all connections and splices for conformity with an instrument designed for that purpose. Checking all connections whether electric or non-electric visually is necessary to prevent a misfire. With more complex delay patterns using non-electric detonators, it is prudent to double-check the sequences of connections to ensure the blast delay pattern will function as designed.
Initiating the Blast
Blasting is a comprehensive process that must consider the protection of the blast area ahead of time. This process must be implemented after the blast is loaded. Implementation begins by deciding what area around the blast to clear and guard. Special consideration must be given to trafficways such as haul roads and public roads.
The blaster-in-charge guarantees the area is secure by (1) doing more than just looking to make sure no one is present and sounding a warning, (2) giving clear information of the firing time and locations to everyone on the site, (3) posting signs and guards at safe locations, or (4) constructing barricades to control access into the site. The blaster-in-charge decides the number of guards needed and coordinates the communication with them. Finally, the blaster-in-charge must make sure that the firing position is at a safe distance and is adequately protected from flyrock.
After the blast area is cleared and code of blast signals is given, the blast is initiated at the predetermined time.
Post Blast Inspection
The final duty of the blaster-in-charge is to inspect the blast site after the blast initiation to determine if any potential hazards were created. The post blast inspection must only be made after the dust and fumes have cleared. If any dangerous rock conditions or unexploded charges are found, then do not give the all-clear signal. Immediately begin actions to remedy all hazardous conditions. Sound the all clear only after all hazards are mitigated. A more detailed discussion of misfires is given later in this book.
Additional Resources
Mine Safety and Health Administration (MSHA). Code of Federal Regulations (CFR), Title 30, MSHA, Washington, D.C.