Historic bridges get no love, at least not from the civil engineering community. If you are a civil engineer, especially a bridge engineer, historic bridges are nothing but headaches. The concrete ones are probably rotted from the inside out, with outmoded and salt-ravaged rebar. The metal ones are riveted. Who does riveting anymore? There may be material loss from rusting. For some of the older ones, no one knows how they function. This isn’t taught in schools any more. For the average engineer, the numbers for rehabilitation don’t work. By the time the bridge gets to the attention of the design team, the bridge probably hasn’t been rehabilitated for 40-50 years. It is unlikely to have been maintained for the last 30 years. Neglect takes its toll. A proper rehab might give another 40 years of life to the bridge at two-thirds the cost of a new bridge. The new bridge would be designed for a 100 year life, and would require little or no maintenance for the first 30 years. Rehab looks like bad math.
On top of that, the oldest bridges, the older metal truss bridges, were never designed for the current loads on the road today. Virtually all of the bridges of this type are posted, from between 3-15 ton. They are narrow, sometimes only allowing one lane. But what has kept these bridges around are two critical factors. For the ones that remain, they manage to meet transportation need. Traffic might be under 800 cars a day, with few trucks. They are in remote areas serving not that many families. There may be redundancy in the network so there is another more recent bridge that can get people from A to B.
The second critical factor is funding. Simply put there aren’t enough simoleons available to bring the entire network up to snuff. For bridges and roads, there is always a delicate dance between putting funding into keeping roads up and keeping bridges up. In any given year, there’s about half enough funding to do everything well. So there are continual compromises. A road might get a bit of maintenance and deferred resurfacing, or resurfacing rather than a reconstruction. A bridge might get posted rather than rehabilitated. Usually maintenance is deferred. In some cases now, bridges are outright removed rather than rehabilitated, because the need cannot be demonstrated and the money is needed elsewhere. State DOT’s and their associated Federal Highway Administration State Divisions allocate funding by regional planning organizations. HATS, or the Harrisburg Area Transportation Study, is my planning organization for Cumberland, Dauphin, and Perry Counties, and their associated 103 municipalities, including my own boro of New Cumberland. For the four years between 2021 and 2024, a total of $266m is allocated. That is their share. That sounds like a lot, but even a small bridge replacement takes $2m. Reconstructing 1 mile of a 2-lane road runs over $5m. The HATS region has over 1,300 bridges and 5,000 miles of road to maintain.
Under normal times and when there is this funding diet, older and smaller historic bridges are protected from replacement because there simply isn’t enough money to get down the priority list to the 300 ADT, 3 Ton-posted structures. Under normal times, need drives the priority list in a very Darwinian way at a local level. The downside of this funding balance is that investment into maintenance of historic bridges is nil, leading to a self-fulfilling prophesy of deterioration and need to replace as the only viable alternative.
The infrastructure bill just signed into law has made this very non-normal times. A total of $110b will be injected into infrastructure over 5 years, of which $40b is for bridges. In addition, the Highway Trust Fund is provided nearly $300b over the next five years, around $60b a year.
Side-by-side you are looking at a total of $50-55b a year in Federal road and bridges expenditures to the states in 2020 being increased to $82b a year in 2022, a 60% increase. These Federal Funds will need to be matched by States in an 80/20 ratio, but I do believe that States will find the 20% to leverage the 80%. From the State’s perspective, it is free money.
Which brings us back to exhibit A, the Biden Photo-Op in New Hampshire. President Biden opens his campaign to sell the infrastructure bill with a photo-op in front of what NPR calls a rickety bridge and which the media describes as structurally unsafe. Structure 028401770014800 over the Pemigewasset River is a 183 foot long steel through truss arch bridge, built in 1939. In its last inspection in 2018, it had a sufficiency rating of 36.9 out of 100. The superstructure (the bridge part for most of us) is rated as 4 out of 10. The substructure – abutments and piers – are rated as 6 out of 10. The bridge currently has an ADT of around 650.
Oh, by the way, the bridge is eligible for listing in the National Register of Historic Places, although that is nowhere stated in articles.
LET’S CLARIFY ONE THING RIGHT HERE, RIGHT NOW! Any unsafe bridge should be closed immediately. Any DOT or bridge inspector that allows an unsafe bridge to remain open should be in jail for criminal negligence. This bridge is not closed. It is unlikely to be unsafe. It is structurally deficient, a term that continues to vex FHWA and bridge managers. FHWA doesn’t even use the term structurally deficient anymore because of the confusion with the public. The new terms are Good, Fair, and Poor with regard to different bridge elements; however, for this post, we will stay with the old terminology.
All bridges are rated on a 9 point system, from 0-9, with 9 being in perfect condition in all ways. The summary bridge rating is a composite of ratings for Deck, Superstructure, Substructure, and Culverts. Bridges with one component in code 4 or less is classified as structurally deficient (Poor). Our bridge superstructure is rated 4, hence meeting that structurally deficient test. The bridge’s sufficiency rating is a composite measure of whether the bridge should be replaced or not. Any rating below 50 recommends replacement. Our poster child bridge’s sufficiency rating is 36.9 and thus is eligible for federal funds for replacement
I’m sure President Biden read from the talking points provided by the NH DOT regarding why this bridge needs to be replaced. Some of which were regurgitated by the press. Overall message: This here bridge is about to fall down and kill people. Infrastructure funding will provide us with a nice, new and un-unsafe bridge.
Correction: It has come to my attention that this particular bridge is going to be rehabilitated instead of replaced, which is probably the right outcome, given the need. Nowhere in any of the press releases is this said, nor is the statement that it is historic. Although this bridge may have a successful outcome, with regard to historic preservation and meeting transportation need, other bridges may not be so lucky. So, I am keeping the rest of the article intact, as the points are still relevant.
Which all goes to show that “need” is a very subjective idea in an engineering world. Do you need to replace this historic bridge if you don’t have the funding and it is meeting some sort of transportation need? Probably not. If all of a sudden, you have these extra simoleons banging around in your pocket, maybe you do need to replace that bridge. Engineers are human, after all.
I don’t want to expend a lot of effort explaining why we should keep historic bridges, or any historic resource for that measure. At least grant me that this is a worthy goal. I do believe there is room to keep historic bridges in state DOT inventories and put them to good use. It does require planning and commitment, even more than funding, although funding is also needed. Congress enacted the National Historic Preservation act over 50 years ago. It remains, largely intact. Section 106 requires consideration of historic resources when Federal funds are used. This includes historic bridges. Furthermore, there is a part of transportation law, know commonly as 4(f), that requires a careful analysis of why a rehabilitation option isn’t “feasible and prudent.”
For this particular bridge, it may be the case that it does need to be replaced, but I am suspicious. (Correction: See above.) First, the bridge is not posted and the ADT is 650. It is on a rural minor collector, with only 10% of the traffic as truck traffic. As recently as 2013, the superstructure was rated fair, not poor, which suggests that maintenance was neglected. The deck is rated poor, but re-decking is a reasonably inexpensive task, actually the least expensive rehabilitation component you can get in a bridge. The channel and scour numbers are not that bad and seem to be stable. Frankly, if I were selecting a bridge for President Biden to be the poster child for the infrastructure bill, it wouldn’t be this one. Unless, NH DOT is trying to send a signal to the preservation community that they’re coming for our rivets.
Engineers have a well-deserved reputation for being analytical. And God help us if the organization responsible for maintaining our roads and bridges was faith-based, instead of analytical. However, too many engineers and DOT managers let the pursuit of the measurable over other values get the best of them. We can appreciate their desire to find the least cost solutions, but if it is at the expense of the environment, or history, perhaps these traits impede their judgement. For the reasons laid out above, most bridge engineers do not have warm feelings about historic bridges, but this does not excuse them from balancing costs and other environmental factors. That is the heart of NEPA (the National Environmental Policy Act) and Section 106 and 4(f). Engineers need to be human, not computational automatons.
Given the opening salvo in the road trip to sell the infrastructure bill is the President in front of an “unsafe” but historic bridge, I fear the prospects for other historic bridges are not good. I wonder how many of these will be swept away in this funding flood? If you are working in a State DOT or FWHA Division Office in historic resources, buckle up. It’s going to be a bumpy ride. If you are in a historic preservation organization, put this on your radar. It’s coming, fairly quickly. If you’re a regular citizen, maybe it’s time to ask your State DOT why the historic bridge in your neighborhood needs to be replaced instead of rehabilitated and whether your DOT is going to give more than lip service to Section 106 and Section 4(f).
Update: November 19, 2021, 3:15 PM
It has come to my attention that the 1939 historic New Hampshire bridge discussed in this article will be rehabilitated and not replaced. It is a better outcome than I had feared, but does not negate the overall tone of press articles and the suggestion that “rickety” bridges such as these should be replaced.