On March 6, 2009, a 125-ft stadium light pole at the Bob Shelton Stadium at Hays High School in Buda, Texas, toppled into the adjacent gymnasium, crashing through the roof and causing extensive property damage. Fortunately, the gym was unoccupied, and the 60 people waiting in the stadium for a soccer game to begin were unhurt. In the last five years, there have been several incidents involving similar stadium lighting poles (Timeline of Stadium Pole Incidents).
The poles in each incident were steel with a galvanized coating, ranging in height from 70 ft to 135 ft. All were manufactured by the now-defunct Fort Worth, Texas-based Whitco Co. LLP and installed between 2000 and 2006. Yet, forensic reports conducted by various engineering firms disagree on the cause of the structural failures.
As a result of these incidents, in April 2009, the U.S. Consumer Product Safety Commission (CPSC), Washington, D.C., issued a press release warning the public, school officials, facility managers, and municipal and public safety officials that Whitco Co. LLP outdoor steel stadium light poles installed between 2002 and 2006 should be inspected immediately by a qualified professional for signs of structural failure, such as cracking and fractures. On its own, a visual inspection — with or without magnification — cannot determine the extent of the flaws.
The applications for the lighting poles comprise recreational and athletic facilities, such as parks, ball fields, and outdoor stadiums, where participants, spectators, and passersby could potentially be put at risk of serious injury and death from being hit or crushed. Therefore, as a matter of public safety, any poles that reveal any of the signs of stress should be repaired or replaced by a qualified professional, advises the CPSC warning (The Fix Is In).
Built to spec
In addition to these specific Whitco Co. LLP poles, the investigation by the CPSC encompasses all other outdoor steel stadium light poles, citing they may pose a similar concern. Although there have been no reported incidents involving other pole manufacturers, the CPSC's report has exposed the lack of regulation over the manufacture, installation, and inspection of sports lighting. Currently, there is no agency responsible for the oversight of stadium lighting pole manufacturing, even for public applications.
“These failures are premature and a big disappointment for our industry,” says Ken Cornett, director of Hubbell Lighting, Inc.'s specialized sports lighting brand, Sportsliter Solutions (SLS), Greenville, S.C., which has had no reported pole failures.
In response to the situation, Cornett advises the sports lighting community to use pole structures built to specifications set by the American Association of State Highway and Transportation Officials (AASHTO), Washington, D.C. “We don't want to ignore the benefit of relying on third-party structural standards in pole calculations just because they're not required,” says Cornett.
The AASHTO standard, found in Sec. 660 of the organization's publication, “Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, 5th Edition,” covers the structural design for highway lighting, specifically high-mast lighting for freeway interchanges. Although most sports poles do not include the high-mast lowering device, Cornett says the requirements for the pole structure still apply. “The two are very closely related,” he explains. “It's the closest product that has a third-party structural standard. They're both tall, round, single poles.”
The AASHTO standard sets forth requirements for the manufacturing process, ranging from the type of welding on the structures to the pole strength calculations. “The highway high-mast structural standard is very robust,” says Cornett. “Sports lighting systems manufactured to the AASHTO standard result in a structure that is much stronger.”
Furthermore, lighting systems for stadium and sports field applications should be specified to the Illuminating Engineering Society of North America's (IESNA) RP-6-01, “Sports and Recreational Area Lighting,” standard, which covers the fundamentals of good illumination, equipment and design factors, power and wiring, illuminance calculations, field measurements, floodlight aiming, maintenance of light levels, and economic analyses. Finally, stadium poles should be manufactured to lightning protection specifications published by the National Fire Protection Association (NFPA), Quincy, Mass. “The NFPA explains what the material should be made of, how tall it should be, and how you carry that current to the ground,” Cornett says.
However, unlike products tested and certified by third-party safety certification and compliance organizations, such as Northbrook, Ill.-based Underwriters Laboratories, which applies a distinguishing mark on the product, stadium poles do not carry a brand that reveals to what standard they have been manufactured. Cornett recommends end-users, such as school districts, tell their contractors they will use only sports poles manufactured to structural calculations established by a responsible, independent third-party organization, instead of the vendor's own calculations.
“It starts with the party who is specifying the project initially,” says Cornett, who advises requesting the actual pole structural calculations that were used to build the poles from the vendor, and then hiring a professional engineer to review those structural calculations to find out if they are in compliance with the third-party calculations. If in compliance, the engineer will stamp and seal the pole calculations, verifying that those poles have been built to the specified criteria.
Get it in writing
Guidelines for installation, maintenance, and testing of stadium and athletic field lighting can take yet another page from the high-mast lighting handbook. The U.S. Department of Transportation's (DOT) Federal Highway Administration publishes “Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaires, and Traffic Signals,” which includes sections on high-mast lighting poles. In addition, many state DOTs maintain their own guidelines and regulations.
These publications emphasize the structural as well as the electrical component of installation and maintenance of the high-mast poles. “The first step is to recognize that a high-mast light tower is not a big light pole,” says Charles N. Landey, P.E., staff member of the electrical operations division of the Wisconsin DOT, Southeast Region, Waukesha, Wis. “It is a structure.”
The foundation design and anchor rod specification must be signed by a registered professional engineer licensed in the site's state who is also familiar with local soils, according to Landey. “If the engineer suggests a soil drilling and analysis, don't cheap out,” Landey advises.
Therefore, Landey leaves the design, maintenance, and inspection of the 77 high-mast light structures under his jurisdiction to structural engineers and independent nondestructive testing facilities. “I should think that by now every state DOT knows this, especially all that liaise with the Federal Highway Administration,” Landey explains. “The people who may not know what to do are truckstop owners, railroads, prison systems, and port authorities, who may sub everything out to an electrical contractor that doesn't have experience with these structures.”
Nondestructive testing is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component, or system without causing damage. Common nondestructive testing methods include ultrasonic, magnetic particle, and radiographic, which do not permanently alter the pole being inspected.
Schools contracting out stadium light pole installation may not be familiar with installation requirements and the fact that the owner should have installation inspection. They often bid the job to an electrical contractor that may be more focused on the electrical component over the poles' structural requirements. “The state governments follows state and federal requirements, and also have their own requirements and people on-site who monitor and document the installation to verify the installation was done to specification,” says Todd Sabo, certified welding inspector and level II NDT technician with TUV Reinland/Non-Destructive Testing Services (NDTS), Grand Rapids, Mich. “In my experience, the electrical contractor gets the job and installs the light poles in accordance with procedures and requirements from the manufacturer, but they don't have any control over how they were inspected and documented.”
In fact, Landey often witnesses the concrete pour for the installation of a new high-mast pole. “I almost always inspect the pour of a high-mast light tower foundation from the beginning to end of the pour — or at least the first two or three units on a given project,” says Landey. “What I am looking for is that each anchor rod must be absolutely plumb. Anchor rods will shift position during the pour.”
Moreover, contractors may be tempted to make changes to the plans during installation. These changes could possibly cause structural flaws in the poles. “The contractor should have the drawings and requirements to make sure the poles are installed properly,” says Bob Bills, CEO of NDTS. “But they sometimes make an alteration without running it by an engineering firm or the manufacturer, and that can create an issue in the future. Most of the errors we find are from improper installation. If they're not installed properly, you're reducing your safety factor right there.”
Landey refers to the documentation of installation as the “inventory system,” which is a written record of all changes to design or installation specifications. “We do that so the owner always will know what was built when, to what specification, and how or if it was modified,” Landey explains. “I capture in writing any deviation from project specifications and save everything. I make sure a number of staffers know where to look for the information for as long a period of time as the structure is in existence.”
Longer life span
Structures for both high-mast and stadium lighting can remain safely in place for up to 30 years. “As a rule of thumb in the highway department, you're building for 30 years at least,” says Landey, noting that in his 20-year tenure with the department, there has never been a structure collapse.
To extend longevity while maintaining safety, the Wisconsin DOT keeps to a strict maintenance and testing schedule. It schedules regular inspections by qualified structural engineers and also performs visual inspections of the towers himself as a supplement to professional structural inspection. “I always find out more by looking than by sitting in the office,” explains Landey, who schedules his visits on days with good visibility but not blinding sunshine. He also brings along a notebook and low-powered binoculars but no camera. “Personally, I'm not big on cameras, because if there is an issue significant enough that it needs a photograph, I'm going to call in the professionals,” he explains.
Each time Landey goes out, he familiarizes himself with the notes from his last inspections as well as the documents from the professional testing facility. He then writes down any visible changes to the pole. Anomalies with newer poles are cause to contact the manufacturer.
Still, not all structural flaws are visible to the eye. NDTS uses certified technicians, such as a certified welding inspector from the American Welding Society (AWS) or level II technicians from the American Society for Nondestructive Testing (ASNT). “The procedure we use is something that we partially developed from the Michigan DOT and the Federal Highway Department, based on the many years of studies done on the reasons for failure of sign structures and luminaires,” says Bills.
The technicians check the general condition of the structure and the coating for corrosion. They also visually examine the transverse welds with high-power binoculars and check the tower for leaning. The critical part of the inspection is to check the base plate connections of the anchor bolts to the structure into the foundation, Bills notes.
Then, the technicians visually inspect the concrete and the anchor bolt hardware (washers, nuts, and thread condition), holding the base plate of the pole down to the concrete foundation. The latter test is performed with a wrench and a ball-peen hammer to sound out if the nuts are not tight. Next, the technicians delve deeper. They proceed with a liquid penetrant and/or magnetic particle test on the baseplate weld to the upright of the pole and an ultrasonic test down the length of each anchor bolt to just below the concrete surface (normally 10 in.) to verify the anchor bolts were not strained during the erection process. If the anchor bolt was overly strained, a crack could have occurred at the thread, resulting in an unfavorable outcome for the structure. “Most of the failures occur at the base of the structure,” he says. “With the record of failures, not only with the Whitco poles, but also with many other structures that we've seen at failure investigations, there should be a regularly scheduled maintenance and testing program, especially for older structures.”
In the Wisconsin state highway system, structures with apparent problems are immediately replaced or, if it can wait, scheduled for replacement as the budget allows. Landey has removed two structures through emergency procedures and replaced several others in a planned manner. “If there is any doubt about the shaft, I take it down,” says Landey. “You need not demolish a structure for a spot of rust, and small cracks can be repaired by qualified personnel. However, those fixes are for newer structures with a complete file on hand.”
Unfortunately, some electrical maintenance crews only attend to the pole every three to five years or when at least six of the 12 lights atop the pole burn out, a practice that's insufficient for detecting potentially significant flaws. “Poles should be included in a regular maintenance schedule like any other equipment in a facility,” Cornett says.
Landey advises a two-year schedule. “Go out a year after they're put up, and then on the third, fifth, seventh year, etc.” In Wisconsin, professional testing is performed on a two-year schedule. “They go out if I see something that doesn't look right,” Landey says. “They don't work for free, but it's a necessity.”
Sidebar: The Fix Is In
In September 2009, the Agua Fria Union High School District, Avondale, Ariz., hired a structural engineer to inspect the stadium poles installed at its schools after the Consumer Product Safety Commission (CPSC), Washington, D.C., notice was posted to the Web site of the Arizona School Facilities Board. By performing an ultrasonic nondestructive test, the engineer found that all 19 structures had to be fixed — 15 at Desert Edge High School in Goodyear, Ariz., and four at Agua Fria High School in Avondale, Ariz. Five of the poles had a “pretty serious indication” of internal structural faults, according to the engineer's report.
Not surprisingly, the original submittal documents revealed the poles had been built by Whitco Co. LLP. When the company declared bankruptcy in 2006, it nullified any warranties or contractual obligations to its end-users. (An investment group purchased the Whitco name in 2006 and retains the branding in name only. Although the company sells light poles, it is not related to the original company.) Many school districts and municipalities have been left with replacement bills upwards of tens of thousands of dollars. A single pole replacement, not counting lights, costs around $8,000.
Fortunately for the Agua Fria Union High School District, Tempe, Ariz.-based general contractor Adolfson & Peterson Construction — the contractor that performed the original installation — volunteered to fix the poles, estimated at $50,000, at no cost to the district. “There was no negotiation with payments,” says Cary Molash, a project manager with Adolfson & Peterson Construction. “We just took it upon ourselves that this needed to get done for the safety of the kids.”
After consulting with the structural engineer and providing him with the original submittal data and pole calculations, Adolfson & Peter Construction, along with the electrical contractor from the first installation, sand-blasted the steel and welded 12 new, half-inch-thick support plates onto each pole. “The structural engineer very quickly got a fix for us, and we went out and executed that fix,” Molash explains. “Once he figured out how they initially designed them, he was able to calculate and design a fix.”
Sidebar: Timeline of Stadium Pole Incidents
In the last five years, at least 80 defective poles built by Whitco Co. LLP, Fort Worth, Texas and installed between 2000 and 2006 have been taken down because of cracks and other signs of structural failure. Following are descriptions of incidents in which the poles fell, but no one was injured:
October 2005: A pole fell at an athletic field at Northern State University, Aberdeen, S.D. University officials determined that a structural failure was to blame, and two other poles were removed.
February 2007: A 1-yr-old, 90-ft pole fell at a field at Worcester Technical High School, Worcester, Mass. Eleven other poles were removed after testing revealed hidden cracks.
April 2007: A 90-ft pole fell at Applebee's Park, Lexington, Ky., where the Lexington Legends, a Minor League baseball team, played.
December 2008: After a 130-ft light pole at the Round Rock, Texas, athletic complex fell, officials removed three additional poles exhibiting cracks. The forensic engineering report by Wiss, Janney, Elstner Associates, Inc., an Austin, Texas-based engineering firm, cited fatigue cracking caused by wind-induced vibrations for the structural failure.
December 2008: A 70-ft pole fell at a facility in the Midlothian, Texas School District. After the incident, engineers called in to test the remaining poles found hairline cracks on three of them, which were then removed. School officials claim they spent $70,000 replacing the four poles and lights. Six smaller poles remain on the district's baseball field. Ultrasonic tests and continued visual inspections performed on those poles indicate an absence of the flaws that plague the taller poles.
March 2009: A light pole fell onto the Hays High School gymnasium in Buda, Texas. Three additional poles were removed the next day after cracks were found upon closer inspection. The follow-up engineering investigation revealed that poor welding of the giant pole to the base plate was to blame.
April 2009: Under the jurisdiction of the Sanger School District, Sanger, Texas, one 75-ft pole and one 90-ft pole fell, shattering the glass of the lamps, and 14 were preemptively removed after a crack on a third pole was found upon closer inspection.
April 2009: Southlake Carroll School District, near Dallas, discovered cracks on three of four poles at its Dragon Stadium, Southlake, Texas.
April 2009: An 80-ft pole fell on Uniontown High School's football field, Uniontown, Pa., during a storm.
If you have information or questions regarding other stadium light poles, contact the Consumer Product Safety Commission (CPSC) at (800) 638-2772 or send an e-mail to email@example.com.
Source: Austin American-Statesman