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Goin’ Underground the Learning curve Nozzleman Qualification for New York City Subway Tunnels By William T. Drakeley Jr. tinstallation of subway tunnels, shafts, and to the requirements of the ACI Shotcrete Noz--certification efforts now fall under ACI Committee C660), with operators certified accordinghe MTA CC/Long Island Railroad/East SideAccess Project is an extension and new cross passages for the New York City metro area. zleman Certification program. These new subway systems and adjoining con- The ACI Shotcrete Nozzleman Certification nections allowed the use of the shotcrete process, program, developed and maintained by ACI Com- based on certain criteria specified by bid docu- mittee C660, is a program for certification of mentation. This was to be the first major infra- nozzlemen employed for the application of dry- or structure use of shotcrete within the boundaries wet-mix shotcrete. While an ACI Certified Noz- of New York City. zleman would be able to demonstrate basic Fellow shotcrete experts and I have watched knowledge and skill in shotcrete application, there this project unfold with a certain level of antici- are other aspects involved in shotcreting in an pation. Our primary preoccupation was to ensure underground environment that require specific proper shotcrete placement was conducted safely additional training. There are many craftsmen in by a qualified workforce in an underground the underground construction community that environment. However, the New York City have skill and experience in concrete, including underground workers—who initially lacked any some experienced in shotcrete application for knowledge of the shotcrete process—needed to ground support and familiar with the needs for be trained and acclimated to the proper and safe safety and work-related qualifications in the application of shotcrete. I was hired to qualify tunnel environment. However, they are not ACI- workers for the project. Once the workers were certified nozzlemen, and, unfortunately, the qualified, I remained on the project as a consul- educational curriculum and the performance test tant and led oversight to the work in progress at (structural test panel) do not directly relate to the request of the project owner. From the outset placing underground shotcrete. The test is there- of the shotcrete production, the learning curve fore not necessarily useful in assessing the ability for proper application techniques had to be suc- of a person to apply shotcrete in an underground cessfully undertaken at an accelerated pace. construction application. Given the unprecedented nature of the project, ACI Committee C660 is not presently consid- the stakes could not have been higher for the ering a curriculum or certification specific to tunnel future use of the shotcrete process in the greater and mining applications. It is important to note that New York City metropolitan area. the original ACI 506.3R was a nonmandatory guide for an engineer who wished to design a program Specifications for nozzleman certification to include in a project The design specifications required each person specification. Even though many specifications list applying shotcrete to demonstrate acceptable it as such, ACI 506.3R was never a certification proficiency, which was defined as application that program in and of itself. In fact, one of the reasons met the requirements of both the specification the guide was officially withdrawn was because of and the proficiency requirements of ACI Com- the confusion it often created when blindly refer- mittee C660, Shotcrete Nozzleman Certification. enced in a project specification. The contractor was also required to provide operators qualified to perform work conforming training to requirements of ACI 506R, “Guide to Due to the lack of official training programs Shotcrete,” and ACI 506.3R, “Guide to Certifica- for shotcrete applications in the underground tion of Shotcrete Nozzlemen” (this document has environment and the overwhelming need for been withdrawn by ACI because all nozzleman such education, we recommended that a program 38 Shotcrete • Summer 2013


2013SumShotcreteEMag
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