which by regulation require a minimum five-person dive team to inspect. Considering that underwater inspections are often conducted by an OSHA-compliant, three-person minimum dive team, this approach could help determine the need to revisit only a specific area with a larger crew, rather than staffing the entire inspection with a larger crew. For longer bridges, this may prove espe- cially beneficial. Ñ Both sonar and ROV technologies may be used during emergencies such as flood events to provide first-response or even mid-event scour assessment (see Figures 12 and 13). The aforemen- tioned autonomous vessel assessment using sidescan sonar provides valuable assistance to the bridge engineer and owner. Similarly, boat-mounted sonar equipment can be deployed imme- diately after high-flow events or after impact events, to identify damage before a dive team can arrive onsite. AUTHOR Dave Severns: Principal - Underwater Inspec- tion Services Lead, Stantec Consulting Services Inc. 6920 Professional Parkway East, Sarasota, FL 34240 dave.severns@stantec.com CITATION Materials Evaluation 81 (1): 36-42 https://doi.org/10.32548/2023.me-04299 ©2023 American Society for Nondestructive Testing REFERENCES FHWA. n.d. “Long-Term Bridge Performance.” Turner-Fairbank Highway Research Center, Federal Highway Administration (FHWA), fhwa. dot.gov/research/tfhrc/programs/infrastructure/ structures/ltbp/. FHWA. 1995. Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges. Report No. FHWA-PD-96-001. fhwa.dot. gov/bridge/mtguide.pdf. FHWA. 2018. Underwater Inspection of Bridge Substructures Using Imaging Technology. FHWA Technical Report FHWA-HIF-18-049. fhwa.dot. gov/bridge/nbis/hif18049.pdf. FHWA. 2022a. National Bridge Inspec- tion Standards. 23 CFR Part 650. Federal Register 87, (88), Friday, May 6, 2022, Rules and Regulations federalregister. gov/documents/2022/05/06/2022-09512 /national-bridge-inspection-standards. FHWA. 2022b. Specifications for the National Bridge Inventory. Publication No. FHWA-HIF-22- 017. fhwa.dot.gov/bridge/snbi/snbi_march_2022_ publication.pdf. FEATURE | UNDERWATERINSPECTION Figure 12. Sonar attached to bucket truck, to evaluate scour during flood conditions. Figure 13. Sidescan sonar output from an autonomous vessel during flood conditions. 42 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 42 12/20/22 8:15 AM COURTESY: BRIAN ABBOTT COURTESY: HYDRONALIX

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