For decades, the tower engineering community has supplied municipal planning departments with Fall Zone Letters to certify that a pole or lattice structure will not collapse beyond a certain radius. No one is sure exactly when or why this became a jurisdictional requirement, but with continued downward pressure on project margins, it’s prudent to ask why this extra work is still required?
“Our industry allowed the fall zone letter to permeate into the jurisdictional thought process, most likely to keep the permit process moving,” says Chris Ply, President, and CEO of Engineered Tower Solutions and a 20-year veteran of the tower industry. ”Fall zone letters became an accepted requirement for the permitting process while ignoring the underlying issue, which is municipal confidence in what we do.”
Planning departments’ insistence on a Full Zone Letter as part of their checklist for permit issuing has paralleled the development of the wireless industry itself. As wireless communications advanced from 1G in the mid-1980s to today’s super-fast 5G technology, the number of wireless towers and small cell installations proliferated as network operators added capacity and coverage in high usage areas. Municipal planners were inundated with permit applications for infrastructure in airports, shopping centers, college campuses, and downtown areas, struggling to keep up. Part of the solution was to ask permit seekers to submit documentation that showed a theoretical fall zone should the wireless structure fail. But why?
“Rather than clarifying that our structures are designed and maintained as any other structure they might be asked to review, we decided as an industry to write a letter to outline some theoretical fall zone if a failure occurred,” Ply continues. “We became very adept at producing these letters for a wide range of tower types and situations, even to the point of modifying existing structures to accommodate a specific fall zone required by a jurisdiction, whether it was formally shown in a zoning ordinance or just required by a zoning or building permit official.”
Compare this to the approach an urban planner would take to a downtown high-rise building. They are never going to require a large setback on all sides of the building based on a theoretical fall zone. Instead, the jurisdiction would require that the high-rise be designed to withstand all code-applicable wind, seismic, and other loading effects without failure.
“We believe that our industry needs to better articulate the engineering that occurs during the design of these structures, for every modification, and in advance of every loading change,” Ply concludes. “It is this thorough engineering process that negates a fall zone. The tower will not fail under the design events when properly maintained.”