Safety Recommendation H-08-018
Synopsis: About 6:05 p.m. central daylight time on Wednesday, August 1, 2007, the eight-lane, 1,907-foot-long I-35W highway bridge over the Mississippi River in Minneapolis, Minnesota, experienced a catastrophic failure in the main span of the deck truss.1 As a result, 1,000 feet of the deck truss collapsed, with about 456 feet of the main span falling 108 feet into the 15-foot-deep river. A total of 111 vehicles were on the portion of the bridge that collapsed. Of these, 17 were recovered from the water. As a result of the bridge collapse, 13 people died, and 145 people were injured.
Recommendation: TO THE FEDERAL HIGHWAY ADMINISTRATION: Require that bridge owners assess the truss bridges in their inventories to identify locations where visual inspections may not detect gusset plate corrosion and where, therefore, appropriate nondestructive evaluation technologies should be used to assess gusset plate condition.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Highway
Location: Minneapolis, MN, United States
Is Reiterated: No
Is Hazmat: No
Accident #: HWY07MH024
Accident Reports:
Report #: HAR-08-03
Accident Date: 8/1/2007
Issue Date: 11/21/2008
Date Closed: 8/10/2010
Addressee(s) and Addressee Status: FHWA (Closed - Acceptable Action)

Safety Recommendation History
From: NTSB
Date: 1/2/2020
Response: From NPRM Response Letter: The National Transportation Safety Board (NTSB) has reviewed the Federal Highway Administration (FHWA) notice of proposed rulemaking (NPRM) titled “National Bridge Inspection Standards (NBIS),” which was published in 84 Federal Register 61494 on November 12, 2019. Through this notice, the FHWA proposes several updates to the NBIS to address Moving Ahead for Progress in the 21st Century Act (MAP-21) requirements; incorporates technological advancements, including the use of unmanned aerial systems; and addresses ambiguities identified since the last update to the regulation in 2009. Additionally, the NPRM addresses the repeal of two outdated regulations: the Highway Bridge Replacement and Rehabilitation Program, and the Discretionary Bridge Candidate Rating Factor. On August 1, 2007, in Minneapolis, Minnesota, the 1,907-foot-long Interstate 35W highway bridge over the Mississippi River collapsed, and about 456 feet of the main span fell 108 feet into the river. The NTSB’s investigation resulted in recommendations addressing multiple safety issues, including those stemming from insufficient quality control procedures on the part of the bridge design firm and concerning the use of technologies for accurately assessing the condition of bridge components where visual inspections may be inadequate. Safety Recommendations H-08-17, -18, and -20 are all classified “Closed—Acceptable Action.” As evidenced by these investigations, the NTSB supports bridge inspections to ensure the safety of the traveling public on the highway system and has issued safety recommendations that have resulted in the creation of the NBIS and improvements to the standards, such as the establishment of fracture-critical and underwater inspections. The key items that the NTSB supports in the proposed regulations are summarized below: • Requiring inspections of bridges on all public roads, on and off federal-aid highways, including tribally and federally owned bridges, as well as of private bridges connected on each end by a public road. • Changing the permissible inspection intervals for bridges, including providing options for more frequent inspections based on certain risk factors. • Establishing documented procedures for timely completion of load ratings. The NPRM proposes that the time allowed for the completion of load ratings not exceed 3 months from when the need for a load rating is identified. Continuing the monitoring of technological advancements to improve the NBIS and updating bridge inspection policies accordingly

From: NTSB
Date: 8/10/2010
Response: The NTSB is pleased that the FHWA collaborated with AASHTO and bridge owners to evaluate alternative NDE tools that comply with this recommendation and the National Bridge Inspection Standards. We appreciate the distribution and web-posting of these tools and the issuance in January 2010 of Technical Advisory T5140.31, Inspection of Gusset Plates Using Non-Destructive Evaluation Technologies, for bridge inspectors. These actions satisfy Safety Recommendation H-08-18, which is classified CLOSED – ACCEPTABLE ACTION.

From: FHWA
Date: 9/24/2009
Response: Letter Mail Controlled 10/15/2009 4:51:01 PM MC# 2090638 - From Victor M. Mendez, Administrator: In our March 23 letter to Acting Chairman Mark V. Rosenker (enclosure 2), we concurred with recommendation H-08-18. The letter indicated that we would identify field-ready nondestructive evaluation (NDE) methods that field inspectors can use to assess the condition of gusset plates on truss bridges. We also indicated that we would remind the bridge inspection community of the expectation that NDE technologies be used to supplement visual inspection, particularly where signs of corrosion are evident. Our response strategy is focused on two primary activities. First, we are developing written recommendations in the form of a technical advisory or directive for the use of NDE technologies to supplement gusset plate inspection when visual techniques are inadequate to determine the extent of deterioration due to corrosion. The recommendations will address the identification of locations where visual inspection of gusset plates may not detect or accurately quantify section loss due to corrosion, and the use of portable or hand-held ultrasonic testing equipment to measure plate thicknesses. These recommendations will serve as the reminder mentioned in our original response. We anticipate issuing the written recommendations this year. The second part of our strategy involves investigating additional NDE methods for use during bridge inspections. The FHWA has initiated research into NDE technologies, with the results to be shared the bridge inspection community as they become available. For additional information concerning our actions to address your recommendation, please contact Mr. M. Myint Lwin (202-366-4589) or Mr. Thomas D. Everett (202-366-4675) of our Office of Bridge Technology.

From: FHWA
Date: 3/23/2009
Response: Letter Mail Controlled 4/6/2009 1:26:07 PM MC# 2090197: - From Jeffrey F. Paniati, Acting Deputy Administrator: The FHWA concurs with this recommendation to supplement visual inspection with appropriate nondestructive evaluation methods to more thoroughly assess gusset plate condition as necessary. Today’s bridge inspection program and processes are expected to supplement visual inspections with nondestructive evaluation where deemed necessary; however, a reminder of this expectation is warranted. The FHWA will evaluate feasible alternatives for nondestructive evaluation of locations where visual inspections may not detect gusset plate corrosion. In addition, the FHWA will collaborate with AASHTO and bridge owners to assess nondestructive evaluation (NDE) methods that can be practically and effectively put into practice in compliance with this recommendation and the National Bridge Inspection Standards. Between now and June 2010, FHWA will make an effort to identify field-ready NDE methods for use by field inspectors in detecting gusset plate corrosion and assessing the condition of gusset plates. Manuals for the application of field-ready NDE methods will be prepared and released to the State departments of transportation and other bridge owners as soon as they are identified and accepted by FHWA and AASHTO. As NDE technology is constantly evolving and improving, this effort is expected to continue beyond June 2010 to expand the list of fieldready NDE methods that FHWA and AASHTO conclude are acceptable.

From: FHWA
Date: 1/6/2009
Response: Letter Mail Controlled 1/30/2009 2:12:58 PM MC# 2090046: - From Thomas J. Madison, Jr., Administrator: Thank you very much for your November 2 1 letter outlining the most probable cause of the collapse of the I-35W Bridge on August 1,2007, in Minneapolis, Minnesota, as well as the coctributing factors. You also discussed three National Transportation Safety Board (NTSB) safety recommendations (H-08- 17 through - 19) to the Federal Highway Administration (FHWA). First, I would like to thank you and your team for performing such a thorough job in the investigation of the collapse and for sharing the interim findings and lessons learned through a series of NTSB advisories and news releases. Based on the interim findings, the FHWA has worked with the State transportation departments and other bridge owners to make sure our highway bridges are safe for the traveling public. The FHWA appreciates the three very fine safety recommendations to FHWA for improving the quality of bridge design (H-08- 17), using appropriate nondestructive evaluation technologies in inspection (H-08-1 8), and enhancing our training courses for bridge inspectors (H-08-19). We have initiated communication with our partners in the American Association of State Highway and Transportation Officials (AASHTO) to address the recommendations to FHWA and the six new NTSB safety recommendations to AASHTO. We are analyzing the final report and recommendations at this time, and will provide a formal response to NTSB with a work plan outlining action items and a schedule for accomplishing them. Thank you again for your letter, and congratulations to the NTSB for a very complete investigation with recommendations for improving the performance of the Nation's highway bridges. If you have any questions or need additional information, please contact Mr. Myint