While in plain sight, the root cause for why potholes are forming rapidly is not visible to most. I am a native San Diegan and licensed engineer who for years has seen our city streets deteriorate from what they once were — beautiful and smooth — to what they are now, potholed and dangerous.
The cause of the deterioration of our streets is very apparent if you know what to look for and know a little of San Diego’s road maintenance history.
You may or may not have noticed that most potholes, if not caused by poor road or asphalt installation, surround areas where our streets have been cut and trenched to repair, replace or lay new pipes or conduit underground.
The reason these areas are more susceptible to damage is a lack of simple and inexpensive maintenance.
It’s at the perimeter of these areas that uneven settling occurs — where the two sections meet (new and old). When uneven settling occurs, small cracks form along the outline of the opening or trench work previously performed. These cracks allow water to permeate to the road substructure below. As water seeps in, it causes the ground to settle. As the settling continues over time, the cracks get larger, allowing even more water to get in.
Adding the weight of traffic, these cracks will begin to split in different directions, causing the asphalt to fracture. After enough fracturing occurs, pieces of asphalt will begin to dislodge from the street. This is how potholes begin to form, and once formed, they are difficult to control or fix.
What most people don’t know is that signs of past maintenance may still be visible on some of our older streets. Some 15 to 20 years ago — maybe longer — the city used to seal these small cracks with tar, preventing water from getting under the asphalt. This simple technique inhibited settling due to water and deterred potholes from forming.
While this process won’t be helpful on roads that are already falling apart, it is still useful on roads in better condition. Tarring the cracks costs a fraction of what the city pays for slurry sealing — in which a thin layer of asphalt is laid over the entire road. Using the tarring process, the city can protect more roads for much less money.
Tarring involves one or two workers using wands that are attached to the rear of a tar truck by hoses. The tar truck slowly moves forward as the workers in the back seal the cracks.
I do not know why San Diego Mayor Todd Gloria cannot find the money needed for street repairs. He seems able to find the money for new pet projects like bicycle lanes and parks — which will also require maintenance in the future.
Most property owners and investors know that maintenance is a necessity, as it saves money in the long run — something the city regularly forgets.
As an analogy, if you have a leaky roof during the rainy season, you don’t spend what money you have to put in a new rose garden — you take care of maintenance issues so they don’t turn into expensive problems you can less afford.
For the city, these expenses come as crumbling roads require more expensive fixes, as well as paying for damage to private property (cars and such damaged by potholes) or litigation and payments for injuries. As the neglect of our streets continues, deterioration will accelerate. Unfortunately, in San Diego, the deterioration is now spiraling out of control.
Where will future money for road repairs come from, you might ask? Is it possible our city government is not maintaining our streets on purpose, letting them get so bad that the voters will be eager to vote for a new tax or bond? If so, I prefer the use of bonds — as the new money is tied to a particular project, whereas taxes usually go into the general budget, which can be spent on anything, not just roads.
I think most will agree that sealing the cracks with tar is less expensive than replacing a street — it is cheap and very effective. Unfortunately, because of blindness or willful neglect, we now must replace and fix a large number of the roads before we will ever need to maintain them.
Mark Doering is an engineer who lives in San Diego. ◆
