High-profile implosion jobs may get a lot of press when it comes to demolition, but the truth is that less than 1 percent of all demolition work stems from these types of projects. Behind the scenes, tackling explosive demolition requires intense preparation, caution and a high-degree of expertise.
Construction & Demolition Recycling (CDR) talked with two of the industry’s leaders in implosion—Mark Loizeaux, president of Phoenix, Maryland-based Controlled Demolition Inc. (CDI), and Mark St. Cyr, safety manager at Detroit-based Adamo Group Inc.—to discuss what goes into a typical implosion job and what it takes to get the job done right.
CDR: What are the typical steps you undertake in between winning an implosion job and the job’s completion?
Mark St. Cyr (MSC): Upon being awarded the job, we work to firm up the schedule for the upcoming implosion. Oftentimes, there is demolition work that proceeds the implosion, so we make certain to keep the scheduled date for the implosion as close as we can to what the original plan was going into the job. We make certain the required licensing is in place for the state the work is being performed in. We develop an implosion plan and procedure to explain the exact plans of our scoped work, and we work closely with governmental agencies in getting the necessary approvals for the explosives to be brought on-site. Special security measures are then put in place while the explosives are on-site. We work closely with existing community organizations such as fire, police, emergency, utility companies and any other agency who may have input into the work or be affected by the work. We attempt to choose a day which is the least obtrusive to the area. Once the date for the implosion is set, we work with local agencies to make certain the community is well aware of the hindrances and potential delays it may experience due to road closures or other impedances due to the implosion. Following the implosion, we perform a thorough inspection of the site to assure the implosion event went as planned.
Upon a successful inspection, the area is released for personnel to enter again and the community or local site restrictions and hindrances put in place are removed to allow for normal operations.
CDR: What types of equipment are needed for a typical project?
Mark Loizeaux (ML): Generally, much of the same equipment used for strip-out operations prior to conventional demolition of a structure will be needed to prepare suitable structures for explosive demolition. This would involve small excavators, skid steer loaders and equipment with hydraulic hammers (for reinforced concrete structures). Larger demolition equipment might be needed to remove low-rise structures surrounding that high-rise structure to be felled. Generally speaking, any demolition contractor would have the equipment needed to prepare most structures for implosion.
MSC: For the typical implosion, there are various types of drilling equipment used. If setting the charges in concrete structures, there are drilling machines used. There is heavy equipment drilling used for extensive drilling, and manual drilling equipment used for tough access or minimal drilling requirements. Special protective barriers for the charges are almost always used to prevent the explosive charges from sending debris to a large area. If setting the charges in steel support structures, we use special torch-cutting techniques. The cutting techniques require propane and oxygen torches with precision cuts being done on the steel beams, columns, rebar or any other steel having charges set in place. Special vehicles with special licensing are required to transport the explosives.
CDR: What are the personnel requirements for a typical project?
ML: The key to a successful project is having someone with a structural engineering background who will fully understand the nature and condition of the structure. That engineer should be comfortable not only with the condition of structures in their static state, but also under loads which the structure was designed to withstand, such as live loads from operations, wind load and seismic loading if the structure is within an active seismic zone. It is helpful if that structural engineer also has a basic understanding of explosives operations and explosives products. Ideally, a blaster with an engineering background is best suited for design of implosions.
Once the structure has been analyzed and the extent of safe pre-implosion modifications has been defined, a project superintendent with adequate structural understanding of the structure and the modifications to be made is necessary to lay out the preparations and structural modifications, whether they are to be performed by the blasting contractor themselves or the main contractor under the direction and guidance of the blasting subcontractor. In all cases, the blasting subcontractor should be required to formally “approve” the modifications to be made and accept them once they have been made per the blasting contractor’s design.
The third phase requires a competent blaster with experience in handling the type of explosives needed for that specific project under the site circumstances in regards to remaining adjacent above- and below-grade improvements.
MSC: There are many personnel requirements to support an implosion. There are defined special licensing requirements for the personnel handling the explosives. There are special laborer burner skills required to be able to cut the steel in preparation for the charges being set. There are special equipment operator requirements for selective demolition to support the implosion, as well as special operator skills to use the equipment drills for explosives. We have a full team of personnel in place the day of the implosion working closely with the police and other agencies to make certain the site is clear.
CDR: What are some of the biggest issues you have to guard against?
MSC: The explosives not all being detonated as planned is the most important item we plan for. To alleviate this risk, we often use redundant wiring of each charge to add a high degree of certainty that the charges will go off as planned. As mentioned previously, the area is scoured following the implosion, and one of the most important tasks is the review of the area to assure all explosives have detonated as planned. A structure not falling exactly as planned is another item we prepare for. We also create an exclusion zone for every implosion. We post personnel on the perimeter to assure this area is clear. Lastly, the induced vibration can be a very important factor if we have surrounding buildings near the implosion zone, so we have to take precautions. We perform extensive vibration monitoring during the implosion to prove we did not exceed specific decibel levels for the implosion event.
ML: There are several things: 1. Making an adequate investigation to determine whether or not a structure can be prepared and safely imploded. Once that determination is made, you decide whether it should be imploded for commercial or other reasons. 2. Understanding the live loads which could be imposed upon a structure in its prepared state when it is most susceptible to premature failure. This has to be communicated to everyone who will operate in the vicinity of the structure to ensure that the prepared structure is not compromised by intentional or inadvertent acts by others. 3. Ensuring that the property owner/client and regulatory representatives understand the importance of establishing and maintaining an adequate blasting area in consideration of the structure being felled, the type/quantity of explosives being used and the risks associated with the project.
CDR: How does risk and preparation increase according to the size and scope of the project?
ML: The risk that increases with the size of a project is generally commercial. That risk associated with preparing a structure is generally related to actual structural conditions, the nature of the force system created within the structure to be felled and the proximity and nature of adjacent improvements to remain.
MSC: The risk and preparation of a job is directly related to the proximity to adjacent structures and whether the job is in a rural or urban setting. For instance, the requirements for taking down the Georgia Dome in the middle of downtown Atlanta are far more extensive than taking down a smokestack at a closed rural power plant in Waterford, Ohio. The risk in each case, along with the impact to the surrounding community, is what directly drives the amount of coordination and preparation needed for the implosion event.
CDR: What types of implosion projects tend to be the most seamless, and what jobs are the most difficult?
MSC: Rural jobs with very little community interaction that are located in an isolated area are the most seamless. The urban jobs in the middle of a town are the most difficult. The other variable that adds a huge degree of difficulty regardless of the setting is how close in proximity we are to other structures. This creates some extensive protection requirements.
ML: Implosion projects designed and executed by an experienced, competent blasting contractor who has the complete professional support of its client, the property owner and regulators will go well. If a blaster ventures too far out of his envelope of experience, risks go up dramatically for everyone involved, particularly under the strict liability nature of explosives handling operations.
CDR: How has technology changed how structures are imploded?
ML: The dependable production of linear-shaped charges that work predictably had a dramatic impact on the range of structural steel projects. The development of non-electric initiation systems dramatically reduced the risk of premature initiation because of static, stray current and other electrical sources.
MSC: The explosives that have been generated from military usage over the years have helped advance the ability to perform more precise techniques.
CDR: What kinds of training or continuing education do you undertake?
ML: CDI has a recurrent training program for our in-house employees that is conducted by in-house senior personnel and third-party specialists.
MSC: There are stringent licensing requirements put in place by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to become what is known as a federal explosives licensee (FEL). There are extensive background checks, fingerprinting and other requirements to get this license. To order and receive the required explosive materials for a given project, you need this special licensing. This licensing, and any required continuing education, varies by state. There are also very specific and rigid requirements for the handling and storage of the explosive materials as required by the ATF.