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The Future of Potholes

It’s around this time of year that the potholes start to open up again around the Kootenays and probably must of  North America. These troublesome portals into the underworld appear most commonly either; at points of high stress in the road surface, or at points of structural weakness that are exploited by water. With the fluctuation around zero degrees that we have been experiencing this winter, alternating precipitation between snow and rain, followed by clear and cold sunny days, it would be fair to say that the roads need a rest, cause they care getting beaten up by the traffic.

PotholeI’ll preface what I am about to say with a quick statement – I do not call myself a pavement design engineer, but I do have experience designing roads, assessing pavement damage and planning for the remediation of roadways. Also, the intent of this post is not to criticize the engineering and design process when it is employed correctly, rather, I’d like to see new ways to make the design and maintenance process more accessible to municipalities and road authorities that are dealing with the problem. Also, potholes are usually one of the symptoms that presents well after tell-tale signs of pavement degradation such as cracking, rutting, shoving, surface ride quality and many other indicators, which points to a need for better monitoring, maintenance and planning – after all, every pavement is going to fail eventually.

Standard road-building or repairing practice in most organizations involved in the construction and maintenance of roads is to ignore the conditions that present in the form of native materials, moisture, drainage paths, road maintenance and snow removal practices, traffic paths and driver habits. It is only on  larger projects such as new highway or freeway designs that a great deal of effort is expended to make sure that the design is suitable for the subsurface conditions – but even then, it is rare to see the other potential conditions to be given any weight, even though, from pavement failure mechanisms in pothole situations, it is clear that these must have an impact on pavement lifespan. Unfortunately for most communities, the time for considering the causes of potholes is long past.

Here’s a quote from a recent article “Get Ready for More Potholes” – PressDemocrat.com:

Of course, it’s no surprise that Sonoma County is beset with potholes. For six years running, the Metropolitan Transportation Commission has named the county’s roads the worst in the Bay Area.

But this may prove to be a bumper year for the nuisances. From July to December, county crews shoveled asphalt mix into nearly 32,000 potholes, 32 percent more than the same period last year. Workers went on to fill an estimated 82,760 potholes during the fiscal year ending June 2009.

Estimates are based on the amount of filling material used and are available only for this year and last, when a new computer program was adopted.

The reason for the rise lies partly with the weather. So far this winter, Sonoma County has received more than double last year’s rainfall, leaving soaked roads vulnerable to hydraulic eruptions.

“When the water gets in there, it’s almost like it’s acid,” maintenance worker Jeff Hurt said Thursday, shoveling cold mix into Lichau’s potholes. “In the summer, we pretty much keep up with them. When it starts raining, it’s almost non-stop.”

Design Standards

Part of the problem is the use of standards or bylaws in design manuals, which outline a minimum thickness of pavement structure for a given class of road, but in some cases, these standards are not adequate for the conditions that present on a site. Adequate knowledge of geotechnical conditions is necessary for a strong, engineered design, and if the design allows water to pond or travel beside the asphalt for an extended area, this is asking for structural problems to occur in the future.

Past Construction Practices

Many of the roads that are failing today with potholes and other forms of failure were never built to  the standard we’d expect today in the first place. I was involved in a project where a highway that was due for resurfacing and cracked beyond belief was dug up for some pipe installations and it was discovered that where the standards specified 300mm of a base material, in some cases there was none, it was built on native material, which definitely would not meet the specification. And in many cases, the decision is to live with the base structure and fix up the surface, mainly because that is all that the available funding will cover.

Maintenance

the chicago wayThere are two sides to the issue of how maintenance affects the formation of potholes, firstly, planning – having an inspection plan that uses a standard condition rating system that is able to be replicated and carried out every couple of years. The second is that the results of these inspections need to be acted on in the form of a capital plan for an appropriate level of remediation or replacement. A standard axiom is that the earlier a road problem is acted upon, the cheaper it will be, the longer a road surface will last.When it has got to the stage of potholes forming, either there is a localized design problem (if most of the road is fine), or the road is in failure mode (if there are numerous cracks – the pothole is just the first of many in this case).

Often later in the spring, the provincial Ministry of Transportation and Infrastructure will put load restrictions on minor roads to reduce deep structural damage as the, often inadequate, road base turns to mush in that state between winter frozen and summer moist/dry. This works to protect roads in their most vulnerable state, but can’t be applied to every road.

Financial Burden

As mentioned, repairing or replacing road surfaces gets more expensive once they’ve reached a tipping point in quality, (well before the point where potholes form, mind you). Some excellent graphics on this concept can be found at PavementInteractive.org. The final graph shows that the cost per lane per mile of road over 50 years is $600,000 with no maintenance and $276,000 with regular seal coat application and overlay. Additionally, with the regular (and overall cheaper) maintenance, the average pavement condition index (PCI) stays at a value of 90, rather than an average PCI of 76, (with a PCI as low as 20 for a couple of years for the no maintenance program).

Also, poor quality roads have a financial impact on the car owners and insurance companies as well, with increased claims for damage, and increased wear and tear on the vehicle, decreasing the value of the vehicle.

But the biggest question has to be where will municipalities and road authorities get the sort of money required to continue paving all the roads? The price of asphalt has climbed in lockstep with the price of oil and the cost of labour, neither of which are likely to retreat. The financial crisis has crimped even the most affluent community’s spending as fears of pension payments, foreclosures and decreasing property values  and revenues hold spending at bay. All while the average age of public infrastructure keeps increasing, inevitably leading to a budget blowout in the future as these deferred costs come back to haunt us.

Back to Gravel?

12_42_05Some communities in the US are returning their beloved roads back to gravel in an attempt to reduce annual costs to a reasonable level. I haven’t head of this yet in Canada, but folks, it’ll come, no doubt about it. This is a really unpopular topic in most circles, but to rein in spending, the expectations of the community regarding level of service need to be considered, and the ability to travel at 45 miles an hour is not a God given right. From the previously quoted article:

In other words, there’s little chance of getting anything close to the $55 million a year Demery says it would take just to keep the county’s roads in their generally poor condition.That’s 10 times more than the county’s budget for pavement preservation.

Against such odds, the Sonoma County Board of Supervisors adopted a dramatic solution — saving the paving upgrades for 150 miles of the most traveled roads and leaving the rest to degrade. The county will still fill potholes and remove other safety hazards throughout the system. But that’s just a Band-Aid, said Rob Houweling, operations coordinator for the transportation department

“Everyday that goes by we’re going backwards,” he said.

Eventually, many roads will be turned into gravel. As early as June, county staff may present supervisors with plans to pulverize several, Demery said…

“As time goes on, there will be more and more roads we have to turn to gravel,” he said. “At some point in time, it makes no sense to keep filling potholes. It makes more sense to just pulverize it and turn it into gravel.”

What other choice do they have, seeing they didn’t maintain the roads in the most cost effective manner possible? Will our roads ever be in as good condition as they are now, ever again?

Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of UrbanWorkbench.com and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada. If I post something here that you find helpful as you navigate the world of engineering, planning and building communities, that’s wonderful. But when push comes to shove: This is my personal blog. The views expressed on these pages are mine alone and not those of my employer.

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