December 2018 Vol. 26, No. 4

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A sustainable local bridge program: what would it take?

closed bridge

The 15,187 county, city, and township local bridges in Minnesota are an essential link in moving Minnesota’s products to market and citizens to their destinations. Unfortunately, like other infrastructure, they do not last forever. Bridges wear out, deteriorate with age, and become inadequate due to heavier loads and more traffic.

According to Minnesota Bridges (December 2017), a MnDOT Bridge Office report, 467 local bridges are in poor condition and in need of repair or replacement. It is important to note these are not unsafe bridges. Public safety is protected by Minnesota’s rigorous bridge safety inspection program. Our bridge inventory is routinely monitored and carefully inspected to meet federal regulations.

Results of these inspections may require posting load restrictions or closing the bridge. Currently there are about 61 closed or very-low-weight restricted bridges. Some of these may be closed because changing traffic patterns have reduced their need. However, the bulk of these posted or closed bridges carry a real cost. They result in detours, lost time, and additional travel costs, and, in some cases, result in safety concerns for emergency vehicles. Farmers have to haul their crops further during the short harvest period, school bus routes are longer, and tourism destinations are less accessible. Emergency access for fire, police, and ambulance takes longer. An ambulance responding to an emergency heart attack call may have to detour several miles.

This article reviews the annual cost of sustaining a safe, adequate system of local bridges and the amount currently being invested in these bridges. The 2017 MnDOT Bridge Office Report, the 2018 Minnesota Infrastructure Report Card from the American Society of Civil Engineers (ASCE), and discussion with bridge experts helped me better understand the problem.

Alan Forsberg, P.E., retired Blue Earth County Engineer

Annual cost of sustaining a safe and serviceable local bridge system

It is difficult to estimate this annual cost; however, by approaching the question in several ways, a credible estimate can be made. Three approaches are considered here.

1. Changes in funding and numbers of bridges in poor condition over time. There are currently about 467 local bridges in poor condition in Minnesota, according to the 2017 MnDOT Bridge Office report. This number will grow as bridges age and suffer heavier loads and more traffic.

Review of the report shows the number of bridges in poor condition declined for several years. During these years, significant state bond funds in the amount of $20 million to $60 million per biennium were available to assist local governments with the replacement of their bridges. This money complemented local, federal, and other town bridge funds, for a total investment in local bridges of about $35 million to $55 million per year.

Since 2006, about $340 million in state bond funds leveraged the replacement of 1,001 local bridges at an average cost of $400,000. However, in recent years, with very limited state funds available and a few very large projects requiring significant amounts of this funding, the number of bridges in poor condition has plateaued and is even increasing.

2. Local commitment to replacing bridges. The local sponsor must pay for costs associated with right-of-way acquisition, engineering and design, removal of the old bridge, and construction of road approaches. Local commitment to replace a bridge, considering constrained local budgets, is therefore a good indicator of need.

According to MnDOT State Aid data, local governments have committed by resolution to replacing 952 bridges (2018–2021 bridge priority list). There are 140 unfunded bridge projects with plans approved or in queue with the state for approval. Based on this data and past MnDOT bridge bonding requests, about $50 million per year of state funding is needed to complement local, federal, and town bridge sources of funding. This would result in a total investment of about $74 million per year in our local bridges.

3. 2018 Minnesota Infrastructure Report Card. ASCE develops a report card on the state of our infrastructure. The 2018 report for Minnesota was recently released. The report shows $100 million per year is needed to replace bridges on the local system in order to sustain a safe system of local bridges.

Considering the three approaches, a total of about $75 million per year from all local, state, and federal sources is conservatively needed to sustain a safe and serviceable local bridge system for Minnesota.

Funds available for local bridges


Town Bridge Fund. About $16 million per year is constitutionally dedicated for replacement of township bridges from the Minnesota Highway Tax Distribution Fund (“state gas tax fund”). This regular, consistent funding has worked well, slowly reducing the number of township bridges in poor condition.

Federal BROS fund. About $5.3 million per year is available through the Federal Bridge Replacement Off-System (BROS) program. This is competitively allocated for bridges over a 20-foot span that are not on the federal highway system (off-system bridges).

State bridge bonds. This program has for several decades provided funds to leverage federal, State Aid, and local bridge funds. From 2006 to 2014, funds in the amount of about $20 million to $60 million per biennium were appropriated. In 2015, $7.4 million was appropriated by the legislature; in 2018, it was $5 million.

Motor vehicle sales tax on leased vehicles. In 2017, the legislature passed a law allocating 13 percent of the sales tax on leased vehicles to assist with local bridge replacement. The first allocation in 2018 provided $12.6 million for local bridges.

Local property tax funds. In 2018, MnDOT State Aid estimated local governments invest about $2.3 million per year. This does not include local bridges replaced with 100 percent local funds where data are not available.

Total local bridge funds available

Combining these sources yields $41.2 million per year (using the 2018 bonding appropriation). This is about $34 million per year less than the $75 million per year needed to sustain a safe and serviceable Minnesota system of local bridges.

Potential for meeting the shortfall

The town bridge money is a regular source of constitutionally dedicated funding available only for township bridges. It appears to be meeting the need, with the number of deficient bridges slowly declining. Funds have typically been available when a township has chosen to advance a project.

The federal BROS fund does not appear to have the potential to meet the need.

The Minnesota sales tax on leased vehicle funds is very helpful because it creates a regular, consistent source of funds. However, it is not constitutionally dedicated and is subject to loss with changing legislative priorities.

State funds in the amount of about $34 million per year, or $68 million per biennium, either through state bonds, direct appropriation, or some other mechanism beyond the sales tax on leased motor vehicles and town bridge funds, appears to have the best potential for sustaining a system of safe and strong Minnesota local bridges.

Some additional considerations

Budget busters. A few “budget buster” bridge projects have taken large amounts of state funding for local bridges in recent years. These are needed projects, but their high cost detracts from the ability to meet the state’s overall local bridge replacement challenge. A separate funding method for the “budget buster” bridges could be considered, or state funding for local bridges could be increased to compensate in the years of these large projects.

Consultant capacity. Local bridge replacement is dependent on private engineering consultants to design them and contractors to construct them. Large peaks and valleys in funding over the years results in an industry losing capabilities in lean years and being overloaded in peak years. This is inefficient. It also makes it difficult for local governments to plan and design bridge investments for the future. A consistent, regularly funded program is needed to maintain bridge replacement capabilities and promote cost efficiencies.

Bonding. New bridges being constructed are durable and strong, with a typical life expectancy of 75 years. Because these bridges have a long-term benefit to the public, bonding is an appropriate financing method.

In summary, local bridges are essential, and a regular state investment is needed. If not addressed, the deferred cost will grow and become ever more difficult to address.

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