Black Hawk Bridge remains closed after movement detected by sensor system over this past weekend

Iowa Department of Transportation (DOT) officials closed the Black Hawk Bridge over the Mississippi River at Lansing late Saturday night, May 17 after movement was detected within one of the bridge piers beyond what is deemed typical and safe, according to DOT standards. Officials say the bridge will likely be closed for at least a week, and perhaps longer, depending upon what an ongoing follow-up analysis currently being conducted might show.

Clayton Burke, Iowa DOT District Engineer and project manager for the new Mississippi River bridge being constructed adjacent to the existing Black Hawk Bridge, shared in a follow-up conversation Sunday, May 18 that the movement in question was detected on the “third pier as you travel east across the bridge.” Burke further confirmed that this new pier movement does not involve the two piers on the same east end of the bridge that had previously shifted and were replaced during the prior bridge closure of two months in length that took place from late February into late April in 2024.

Burke further explained that two of the multiple monitoring systems of movement detection being used on the bridge sent alerts to those the system was designated to inform, including himself at approximately 10:30 p.m. Saturday night. He said the engineering firm in charge of the monitoring system recommended the bridge be closed immediately after those monitoring alerts indicated the pier had shifted “about an inch, which is beyond the safety threshold we have established.”

The multi-faceted monitoring system being utilized on the bridge includes a GPS (Global Positioning System)-based process that continually feeds pier location data into a computerized graphing system, as well as a tilt meter system, both of which indicated movement in that third pier Saturday evening, Burke shared. He also explained that a vibration sensor system also in place on the bridge did not show any significant vibration readings.

Burke outlined Sunday that the next step was to, first, determine the validity of the monitoring system readings, which he noted would be further determined by a land surveying process that is also part of the bridge monitoring process. He noted that the land survey readings would be compared with the sensor data to further confirm their validity.

In a final update prior to this week’s print deadline, Burke confirmed that the land survey process that was completed Monday, May 19 has, indeed, validated the monitor readings that indicated movement of the bridge pier. He said now that the sensor readings have been determined to be valid, a “very detailed and thorough analysis” is in the process of being conducted to determine the safety of the bridge and the next steps required to be taken in order to open the bridge back up, with that process involving a variety of analytical calculations. Burke suggested that analysis should be completed sometime later this week and will further determine the next course of action for the Black Hawk Bridge.

“Our engineering firm will analyze the bridge to see if it is safe to reopen,” Burke shared. “A timeline for reopening of the bridge will be established after the analysis is complete.”

As to the cause of the movement in that third pier, Burke explained that there were initially a pair of potential causes that were being looked at in regard to the shift, including potential oversized traffic loads, which could be determined by viewing available camera footage. He also said that, adjacent to the existing bridge, there had been some pipe pile driven into the ground Saturday by a vibrating hammer as part of the construction process for the new bridge, but he also clarified that process had been previously tested and determined to have no impact on the existing bridge. Burke said if that pile driving is determined to be the cause of any shift, it will then need to be determined why that activity impacted the bridge at this point after not having done so during the testing process.

Burke did point out that bridges consistently move with temperature and other weather impacts, expanding and contracting as the temperatures rise and fall. He also explained that the weather-related movements are well-documented, and this latest movement was a bit beyond any of that, in addition to being beyond the threshold that officials deem safe to have the bridge open to traffic.

Initial speculation was that, at a minimum, the Black Hawk Bridge would be closed for the remainder of this current week, with Burke noting the actual length of closure will depend upon the analysis currently being conducted. He did assure that crews are doing, and will do, everything they can to get the bridge back open as soon as possible.

Additional updates on the bridge closure can be found at 511ia.org and on the bridge construction project’s Facebook page at Mississippi River Bridge at Lansing.