Minnesota Department of Transportation

511 Travel Info

Hwy 43 Bridge


Work package #5 and #6 costs

Questions and answers

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Select a question below to see its answer at the bottom of the page.

  • Question 1
    A change or evolution of bridge design standards was one reason expressed by MnDOT as contributing to the cost growth for work package #5. Please provide detailed background information as to how and why this occurred.
  • Question 2
    Who made that decision?
  • Question 3
    Over recent years, MnDOT appears to have transitioned from HS 20 to HL 93 standards for bridge rehabilitation projects. Could you describe that transition? What rehab projects started become subject to the new standard? When?
  • Question 4
    Did the FHWA set deadlines for transition to using HL 93 load rating for evaluating in-place bridges? If so, what were those deadlines?
  • Question 5
    MnDOT has listed a faster than planned deterioration of the bridge as one of the reasons for the cost increase. I have looked at the MnDOT bridge inspection reports and don’t see the same thing. I feel I have a good understanding of these reports.
  • Question 6
    I was wondering why a four-lane solution was proposed for the Winona bridge. The east bridge from the island into Wisconsin is only two lanes, so it doesn't seem to make sense from a traffic standpoint. Why not just build the new two-lane bridge for vehicle traffic and then convert the existing bridge into a bicycle and pedestrian bridge, like what is going to happen with the Stillwater Lift Bridge? I would think rehabilitation of the old bridge for pedestrian and bicycle use would be far less expensive than a rehab for car/truck use.
  • Question 7
    Has the idea been considered to rehabilitate the existing bridge as a bicycle pedestrian crossing only, and defer options for four lanes for motorized vehicles until when and if traffic volumes ever justify it? I would think rehabilitation would be cheaper if it had to support only the dead load plus bicycles and pedestrians and would last longer without salt spray.
  • Question 8
    Is CMGC to blame for the cost overrun?

Answer to Question 1

Prior to Sept. 10, 2013, the bridge design protocol that MnDOT used was the Load Factor Rating (LFR) method. This used an HS-20 design vehicle. On Sept. 10, 2013, the MnDOT Bridge Office Policy Committee discussed establishing a policy regarding the appropriate design code to use for bridge repair and rehabilitation projects.

Given that the AASHTO Standard Specifications for Highway Bridges have not been updated since 2002 and have several documented deficiencies, the committee agreed that repair and rehabilitation projects should be evaluated and designed using the current edition of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications, along with the latest Load Rating/Load and Resistance Factor Rating (LRFR) requirements from the Manual for Bridge Evaluation (MBE).

The AASHTO LRFD Bridge Design Specifications are founded in the latest research — incorporating the variability in material properties and loading, as well as being statistically calibrated to provide uniform reliability. There are many differences between LFR and Load and Resistance Factor Rating (LRFR), one of which is the design vehicle. As previously mentioned, LFR uses HS-20 and LRFR uses HL-93. See background on HS-20 and HL-93.

All new bridges that MnDOT designs use the LRFD methodology. Many states, including Minnesota, use the AASHTO LRFD Bridge Design Specifications as the framework for their design, but with modifications as set by policy groups that focus on specifications of state-specific issues. One example is states with larger legal or permitted loads designed for vehicles, beyond the HL-93 notional vehicle that is specified in AASHTO.

MnDOT policy is to always use the modified HL-93 double truck loading (110% instead of 90% as spelled out in AASHTO) to encompass the loading we see from our permit vehicles. The guidance can be found in the MnDOT LRFD Bridge Design Manual on pp. 3-5. Originally, it was included in the BDM on February 14, 2015 as part of a memo to designers (2005-01) and was incorporated into the text of the manual in 2015. This is the bridge design protocol used in the Final Design for work on the existing bridge for work package #5.

Answer to Question 2

The Bridge Office Policy Committee consists of technical experts from all three sections of the Bridge Office – planning and hydraulics, design, and construction and maintenance, as well as a representative from the Federal Highway Administration.

Answer to Question 3

Since Sept. 10, 2013, transition projects were handled in three categories:

1. Final design after Sept. 10, 2013: Follow LRFD specifications.
2. Final Design at 60% stage or greater: Allow LFD specification but encourage LRFD if schedule allows.
3. Final design less than 60%: Follow LRFD specs unless scheduling challenges in completing plans.

Answer to Question 4

There is no deadline set by FHWA for evaluating inplace bridges. All new bridges must use LRFR.

Answer to Question 5

See the PDF.

From Jennifer Zink, MnDOT State Bridge Inspections Engineer:

In this PDF are shown portions of the fracture critical inspection reports from 2008 to 2014, which give a comprehensive view of the increased deterioration of the bridge. As these reports in their entirety are hundreds of pages long, only certain pages are included due to file size.

In both the 2008 and 2010 inspections, note the highlighted portion of the NBI summary sections. They show an intermediate drop in the NBI rating for the Superstructure due to condition. An NBI rating below 4 requires immediate action. NBI ratings are only reported to the FHWA once per year typically in March. So as a result, by the time this is done, the NBI has been upgraded back to 4 or above by that time due to immediate action on the bridge.

Also note the change in element condition ratings from each year (located near the middle to end of each file). I’ve highlighted the elements mainly pertaining to the truss - both the deck trusses and main through truss spans. As with NBI ratings, element ratings can be upgraded to a certain point if any repair or deterioration mitigation efforts are made. I have also included the NBI historical condition summary of the bridge showing the changes over the years.

I'd like to stress the difference between inspection types - routine as opposed to fracture critical – so people can understand why there was may not be a SIGNIFICANT change in the inspections from year to year. The definitions of these inspection types per the National Bridge Inspection Standards (NBIS) are as follows:

"Routine inspection: Regularly scheduled inspection consisting of observations and/or measurements needed to determine the physical and functional condition of the bridge, to identify any changes from initial or previously recorded conditions, and to ensure that the structure continues to satisfy present service requirements."

"Fracture critical member inspection: A hands-on inspection of a fracture critical member or member components that may include visual and other nondestructive evaluation."

"Fracture critical member (FCM): A steel member in tension, or with a tension element, whose failure would probably cause a portion of or the entire bridge to collapse."

"Hands-on: Inspection within arms-length of the component. Inspection uses visual techniques that may be supplemented by nondestructive testing."

In accordance with these definitions, a routine inspection is much less "in-depth", and usually does not include non-destructive testing techniques such as ultrasonic thickness measurements, as is done with fracture critical inspections. Although significant change may not be reported in a specific year or inspection, that in itself is not indicative that there was no continued deterioration to some degree. The section loss element, for instance, provides percentages that can encompass a wide array of losses.

Condition State 2: Steel element has moderate section loss (from 2% to 5% of the total cross-section area). If the steel element has been recently repainted, any previously existing section loss is not severe enough to warrant structural analysis (less than 10% of the effective section).

Condition State 3: Steel element has significant section loss, but structural analysis is not yet warranted (section loss is less than 10% of the total cross-section area) or structural analysis has determined that the existing section loss has not significantly reduced the structural integrity of the element.

Condition State 4: Steel element has severe section loss (more than 10% of the total cross-section area). The load-carrying capacity of the element has been significantly reduced - structural analysis or immediate repairs may be required.

Also, it is not uncommon for bridges to not show significant increased deterioration over a short 12-month period, especially when seasonal cycles are less severe than in past years in regard to snow and ice events. However, as with any bridge of this vintage, once moisture and salt is introduced to steel members, continued deterioration is inevitable and can grow exponentially as the bridge ages. Mitigation efforts such as painting, reinforcing, and/or caulking elements can slow down the process, but is only a temporary means.

I invite you to look at the Bridge Office inspection website for further information, especially in regards to our field inspection manual - Chapter B of the Minnesota Bridge and Structure Inspection Program Manual. The field manual defines the different NBI and element rating condition states. It also covers information on sufficiency ratings. The websites for MnDOT Bridge Inspection information and the manual are:

If you have any further questions, please don't hesitate to contact me.

Answer to Question 6

A four-lane solution was supported by state and local leaders in September 2012. To maintain traffic across the river during the proposed rehabilitation and reconstruction of the existing bridge, a temporary bridge was deemed necessary at an estimated cost of $30.7 million. It was felt a better use of these funds would be to put them into the cost to build a new bridge.

This option was included in the Environmental Assessment (EA) for the project and was eventually approved. The Federal Highway Administration (FHWA) capped the federal participation in the new bridge construction at $30.7 million. Had we used the temporary bridge approach, we would likely be under budget for the overall project.

Since we have hit the “pause button” and all options should be considered to be on the table, it may emerge once again. It is counterintuitive, however, that from a bridge structural design perspective, the existing bridge must be stronger to support pedestrian loadings than traffic loadings (unless all pedestrians would be channeled onto a narrow corridor on the structure). This is due to the potential for the bridge to be fully loaded with pedestrians (shoulder-to-shoulder, for example), which is more loading than what is expected by vehicles.

Answer to Question 7

We believe you will find the answer to this in Question #6.

Answer to Question 8

There are chapters left in the CMGC story on the Winona Bridge project, in regards to CMGC. The Winona Bridge Project team feels CMGC actually positioned MnDOT and all project partners better than the traditional design-bid-build procurement methodology likely would have. Watch for future installment #5 to this website, in regards to the CMGC procurement methodology on the Winona Bridge project.