The Fascinating Pothole Story

Why are there so many potholes in Fairfax?


First it's important to recognize how roads deteriorate. Right after paving, there is a tarry surface that keeps water out of the asphalt (a mixture of tar, sand, and gravel). After a couple of years, little cracks form, and water sits in those cracks.


This is important to know, because there are organisms that live in water, that like to eat oil products, in this case tar. With some of the tar in the cracks now eaten, the sand loosens up, gets washed out of the cracks, and they get bigger. More water fills the cracks, and they grow faster. You've probably seen extra tar poured into the cracks on roads, and this is why – to keep the water out.


After about the 5 year point, these cracks will be covering the surface, so that the road soon looks like it's made of a bunch of blocks, like an alligator's skin. Each of these blocks is getting smaller, because they are getting eaten away, with the cracks getting bigger. Cars and trucks driving on this often move these blocks a little, making cracks below them. As soon as one comes loose, you have a hole, and guess what? It fills with lots of water, and oil–loving bacteria. Soon the gravel comes loose, too, and you have the classic potholes, that seem to appear overnight.


At the 10 year point, often a heavily used road will have lots of holes, and cracks that are ready to become holes very soon. The only way to fix it if it gets bad enough is to grind it all out, and rebuild it from scratch. Very expensive.


Now here is a really important fact: if you re-seal the road at the 5 year point, you can re-set the clock to almost zero. This is called slurry-sealing, and it costs only about 5% of what rebuilding the road costs. You can do this every 5 years and get your roads to last 30 years plus, without potholes. If you don't, they might last only 10.


So back to the local part of the story:


In the 1980s and 90s, the Town Council lived within their means by deferring road maintenance. Not much sealing of the roads, just occasionally filling in the bigger holes. By 2000, this had become a big problem, so Fairfax voted in Measure K, a bond measure legally restricted only to fixing roads. By then, the roads were pretty bad, and the Town rebuilt the worst of them, but certainly not all of the worst ones. Roads that were in better shape got left behind, too. By 2008, all of the Bond money (separated into three bonds) was used up.


The bigger problem is this: Roads left unmaintained deteriorate faster than the debt in the bonds - we will be paying these bonds off over 20 years.


When I was elected to the Council in 2009, I started working on the problem, and oversaw a couple of refinances of the bonds, using the lower interest rates then available to pull more money out for the same payments. This has gone into road maintenance, often in the form of slurry-sealing.


I have been working with Barbara Coler especially to develop income streams to keep ahead of our road maintenance. This has been from a number of sources, like Measure C, gas taxes, and the like. We have also worked to identify & prioritize the roads which a) are salvageable and are candidates for protective slurry seals; and b) are hazardous and must be fixed promptly for public safety. This process of evaluation takes a little time but is worth it.


Our roads are now all graded on a scale of 1 to 100. 1 being basically gravel, and 100 is new. The 5 year point referred to above is about 75, and slurry sealing then gets us back to about 98. At ten years old, unmaintained roads can be getting down into the 50 range, and once you are below 45 or so, you are paying for a whole new road, as it needs to be ground out and rebuilt.


Remember, slurry sealing costs only 5% of a new road. Do it in time and you get 5 more years. Then do it again. And again, for 30 more. Approached this way, you get a road that lasts 30 years for 30% of the cost of rebuilding once.


We are not at the point where we can just slurry-seal everything yet, as we are still playing catch-up from the neglect of past years. But I think that this is the right philosophy.


Kind of like brushing your teeth now, to avoid a root canal later. Which would you choose?