The NDT Library offers more than 2400 papers and proceedings from ASNT’s respected journals and acclaimed events including the Annual Conference and Research Symposium! ƒ Easy search features let you find wh t you need fast. ƒ Access to free content for ASNT Members! ASNT… Creating a Safer World!® Start your search today at ndtlibrary.asnt.org Take Us With You Stay informed with Chat NDT with ASNT—the podcast for NDT professionals featuring the latest information and interviews about the NDT industry. ASNT… CREATING A SAFER WORLD!® asnt.org/chatndt 2301 ME Jan New.indd 35 12/20/22 8:15 AM

UNDERWATER INSPECTION OF HIGHWAY BRIDGES – RECENT TRENDS AND TECHNOLOGIES BY DAVE SEVERNS, P.E. Underwater engineering evaluations of transportation assets have historically relied largely upon conventional, crewed commercial diving operations, using visual testing (VT) and tactile examination methods to detect surface discontinuities and evaluate site conditions. In practical application, this approach alone is often found to be suboptimal, due to multiple challenges inherent in conducting inspections in the underwater environment. Modern underwater inspections are increasingly reliant upon new technologies, and nondestructive testing methods beyond VT are used during conventional diving inspection to gain a broader picture of the asset and its condition, increasing efficiency while lowering risk in the process. Underwater engineering inspectors today employ traditional nondestructive technologies, including VT, ultrasonic testing (UT), and magnetic particle testing (MT) techniques, in concert with acoustic (sonar) imaging techniques and remotely operated vehicles (ROVs) to obtain more detailed information about the asset and adjacent waterway conditions. This approach enhances the inspection’s safety and efficiency and reduces risk to the bridge owner and end user. This article discusses today’s underwater bridge inspection approach, emphasizing the NDT technologies utilized and their benefits. Introduction As transportation assets within the United States continue to age, the need to manage their performance and ensure their safety becomes increas- ingly important. This is especially true for the nation’s bridges, which rely on periodic safety inspections to assess con- dition and determine needs for main- tenance, repair, and eventual replace- ment. Bridge safety inspections are mandated by federal regulation, falling under the jurisdiction of various federal agencies including Federal Highway Administration (FHWA), US Department of Defense, Bureau of Reclamation, Bureau of Indian Affairs, US Forest Service, and others. According to 2021 National Bridge Inventory (NBI) data, there are approximately 500 000 bridges in the United States that span waterways. Of those, nearly 30 000 bridges exhibit submerged substructure elements that require stand-alone underwater bridge inspection. This article will discuss the historical state of practice regarding con- ducting regularly scheduled National Bridge Inspection Standards (NBIS) underwater bridge inspections, includ- ing their use of NDT techniques, as well as a newer, more innovative approach marrying conventional, commercial diving techniques with more advanced nondestructive technologies, including sonar imaging and remotely operated vehicles (ROVs). Some example proce- dures employed in this enhanced work approach will be presented, along with their advantages. Historical Inspection Approach Underwater engineering evaluations of bridge assets have historically involved conventional diving operations, using visual testing (VT) and tactile examina- tion methods to detect surface discon- tinuities and evaluate site conditions. Underwater inspections are required on a maximum 60-month inspection interval for all highway bridges in the United States, as per 23CFR650 National Bridge Inspection Standards (NBIS), with oversight provided principally by the FHWA as well as individual bridge owner-agencies. Aided by high-intensity underwater lamps and small hand tools to facilitate cleaning and rudimentary measurement, the formally accepted inspection practice is for the inspec- tion team to conduct a “Level I” “swim by” cursory inspection of the asset, in conjunction with a “Level II” hands-on, tactile examination of the asset elements, involving the localized removal of bio- fouling to expose the element surface. Unless otherwise scoped, the use of specialized testing to evaluate material properties or identify subsurface condi- tions has typically been conducted on an as-needed basis, as a “Level III” detailed, or “in-depth” inspection. The water body spanned by the bridge is also typically evaluated during the underwater inspection, to evaluate both geomorphologic aspects (the shape and physical characteristics of the waterway) as well as to detect scour (erosion of the banks and underwater channel bed caused by flowing water). Waterway inspection procedures during a typical NBIS underwater bridge inspection rely on VT, in conjunction with a conventional echo-sounding fathometer, to chart channel bottom profiles both along the exterior edges of the bridge as well as adjacent to individual substructure units. Channel bottom depth data is post-processed and converted into elevations, which, in turn, can be compared to past data as FEATURE | 36 M AT E R I A L S E V A L U AT I O N • J A N U A R Y 2 0 2 3 2301 ME Jan New.indd 36 12/20/22 8:15 AM