There has recently been some letters and opinions about potholes printed in TGI so I wanted to add some insight to the situation.
When it comes to fixing the potholes in our roadways and highways, I think our county and state workers are doing the best they can with the resources that are available to them. The methods used are likely not the most efficient but that’s just how they’ve been taught … or not taught.
The repair treatments of yesteryear may have been sufficient then, but with the ever-increasing traffic and population, and the advancements in technologies, newer and more efficient repair treatments are way past due.
It’s the Hawaii standard treatment to all problems — “Reactive, rather than proactive” — which ultimately results in an increase in taxes.
Potholes that are not being sealed or compacted properly is likely not the primary cause of the short-lived repair.
First of all, remember, asphalt concrete (AC) is composed of sand, gravel and asphalt. Asphalt is an oil product that acts as the bonding agent.
“Asphalt” is a dark brown to black, highly viscous, hydrocarbon produced from petroleum distillation residue. This distillation can occur naturally, resulting in asphalt lakes, or occur in a petroleum refinery using crude oil.
We all know that oil and water do not mix. Therefore, water is the No. 1 enemy of asphalt concrete pavement. The No. 2 enemy is vibration, but we’ll leave that alone for now.
Did you ever notice that more potholes appear when we’ve had a lot of rain?
Did you ever notice a lot of brown muddy water coming up through the cracks in the pavement usually in depressions in the pavement surface?
This is caused by runoff water that has permeated and saturated the ground beneath the AC surface. That water quite quickly deteriorates and destroys the bonding of the AC from the bottom, and with the aid of the wheel loads and vibration of the traffic above, the broken-up pavement is shoved down into the mud below, pumping the brown muddy water up to the surface.
The goal of a good long-lasting roadway or highway is keeping the asphalt concrete pavement sealed. Both on top and under it.
So how does the water get under the asphalt concrete? While it’s true that much of it seeps into the cracks in the surface, most of it soaks in from somewhere else.
The typical design standards for all roadways include a “cross fall.” That is, the centerline of the roadway is higher then the edges of the roadway typically a 2 percent slope. That’s about 2 1/2-inch of drop for every 10 feet of width. This allows the water to flow off the roadway surface to the edge of the roadway. Once the water is to the side of the roadway, it is very critical that some means of drainage from that point is provided. This is absolutely necessary to prevent the water from permeating under the pavement.
Next time you’re driving on a Kauai road that has a lot of potholes, take notice of where these potholes are located. They’re almost always in line with where the right wheels of your vehicle travel. Right? But notice that in many cases the pavement failure is adjacent to, or near an area where runoff water sits alongside the roadway. That water has nowhere else to go so it seeps in under the pavement.
To prevent this, it’s critically necessary to have some means of drainage to take this water away from the roadway.
Besides a “cross fall” on the typical section of a highway, a “grade” is also standard. All roadways and highways (except here on Kauai) are designed with a “grade.” Which means that you’re always driving uphill or downhill. This is not done to affect how people drive, but is done to provide the ability to drain runoff water.
Highways, roadways and even roads in residential tracts today are designed and constructed with cross falls, grades, and curb and gutters. Water falls on the pavement, flows to the side of the road due to the cross fall, collects in the gutter, and flows along the gutter due to the grade, and eventually falls into a catch basin which has a storm drain pipe connected to it to take the water away. From there on the science of hydrology and hydraulics takes over so I won’t go into that.
Our roads here in Kauai have been roadways for a hundred years or more. Back then, cross falls and grades were likely not even considered. While many of them have been repaired many times and even widened, cross falls and grades are still not a consideration. So the problem of ponding runoff water remains the culprit of the potholes.
A proactive approach would be to remedy this problem by ultimately redesigning and reconstructing our roadways to more current standards, with cross-falls and grades and curb and gutter and storm drains. Of course, the one thing standing in our way in this and every other needed improvement is money. Or, the lack thereof.
So perhaps, there’s an alternate solution.
Perhaps having a real engineer or two survey all our roads for potholes and make note of each location; then study each location to determine the cause of the pothole and make an honest and professional determination as to how to correct the problem.
Eliminate any ponding situation adjacent to the pavement.
Regrade the shoulder in a manner to provide drainage or at least relocate the ponding away from the pavement.
This is the proactive approach to the problem.
Now let’s see if our county crews can handle that without an increase to the GET.
Larry Arruda is a resident of Wailua Homesteads.