Railway Track & Structures - March 2009 - (Page 28)

INSPECTING FOR BUGS or simply false positive results, precluding accurate identification of FST presence. These evaluations were augmented with a scanning microwave detection device (Termatrack®), which worked well when the horn could be braced or held in place without the operator touching it. To facilitate a better reading, a simple brace that attached the unit to wood was used to reduce handler interference. The infrared camera was generally unsuitable outdoors for evaluation of FST infestation on bridges due to the heat generated on these bridges under Texas weather conditions. Railroad engineers frequently inspect wooden timbers by sounding. This technique simply uses a large hammer or mallet to listen to the interior integrity of beams by the resonance of the echo after striking the wood. The standard policy when investigating beams is to drill with a one-halfinch drill bit directly into beams that appear to have a distinct hollow sound when struck with a hammer or mallet. When this was performed, the Boroscope™ was used to visually see what was inside the beam to confirm the presence of FST. In most instances, the Boroscope™ was not needed as FST readily came out of the drilled holes. Their aggressive defensive behavior made it readily clear there were problems in the respective wooden beams and pilings. Activity within Sentricon® monitors has been consistently evaluated, and when attack of wood insects has been detected, Recruit IV ™ Bait containing noviflumuron (0.5 percent AI) was administered in accordance with manufacturer’s recommendations. Subsequent baiting was maintained as needed until population control or elimination was achieved. In some instances, existing bait stations were augmented by adding additional stations in the direct proximity to their existing locations. The largest of these structures, the Green’s Bayou Bridge, was located just south of I-10 East in Houston. It was completely dismantled due to the significant infestation of FST. An analysis of the damage from FST to this bridge revealed 18.3, 5, and 63 percent of the pilings, caps and stringers, respectively, were infested by FST on Section A. Twenty-six, 32, and 44.5 percent of the pilings, caps and stringers were infested by FST on Section C, respectively. Section B (the middle portion of the bridge) was concrete and steel, and was not included. The total infestation of FST on this 300-foot-long bridge was calculated to be 22.6, 20, and 36 percent of the pilings, caps and stringers for all evaluated wood components, respectively. This bridge was replaced with a concrete bridge at a cost of $3 million and was completed in only one week. Safety and rail traffic costs were the principal reason for the expeditious construction of the new bridge. The Seabrook Bridge, Jenkins Park Bridge in Baytown, the bridge at Milepost 8.61, the bridge at Milepost 45.12 near Dayton and the bridge at Mile post 400.6 near Huffman were all treated for FST using either inground or above-ground Sentricon® bait stations. Continuous monitoring was performed to determine FST activity over time. Each bridge had components (ties, braces, caps, and stringers) replaced prior to the initiation of baiting. The combination of removing FST infested timbers and baiting was highly effective in these trials. There were no current infestations at any of the bridges evaluated in this study when monitoring was suspended. However, some bridges were in areas with significant FST populations, and www.rtands.com the installation, monitoring and record keeping for these bridges. Detection of FST was achieved principally using acoustic devices (AED-2000), infrared cameras (IR-InSight™, Infrared solutions, Fluke Corp., Everett, Wash.), scanning microwave detection (Termatrack®, Protec USA, Coral Gables, Fla.) and visually, either by eye or with the assistance of a ProVision 2300 Borascope™ (Alpha Aviation, Burnsville, Minn.). Upon detection of FST infestations, an assessment of the overall level of infestation was determined and their locations in the wood were mapped. In some extreme situations where infestations were exceedingly high, presenting obvious hazards, the railroad removed and replaced wood pilings, ties, stringers and other infested materials. Where FST infestations did not represent an immediate hazard, populations were baited using Sentricon® Baiting Systems (DowAgroSciences, Indianapolis, Ind.) for population reduction/elimination measures. Thereafter, monitors placed at these locations were continuously monitored for three years. Of the six bridges, only one was completely replaced, while others were continuously monitored by a private pest control firm with findings reported to Texas A&M. All inspections and subsequent monitoring of bait stations required the presence of railroad personnel. Inspections on elevated rail bridges were assisted with specialized rail cars equipped with personnel buckets. Initial inspections using the AED-2000 acoustic device were highly successful at locating FST infestations in pilings. Due to vibrations and the difficulty of operating along a railroad, there were sometimes inconclusive audible results 28 Railway Track & Structures March 2009 http://www.rtands.com

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Railway Track & Structures - March 2009

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