Gravel runways are a cost-effective way to outfit small private airstrips, local airports, and commercial operations in remote areas. They are, however, not without their challenges — but with the proper care, they can be one of the best options available.
Especially at remote areas and small airports, gravel runways are advantageous in both their cost and their level of maintenance. Inexpensive materials and less upkeep make them the preferred method of surfacing in many areas, particularly those that experience severe or constant frost. The extreme climates, however, make the upkeep of the runways a difficult task.
Advantages
Gord Drysdale, President of CBR Technology, Inc., outlines the advantages of unpaved runways in his presentation, “Meeting Unpaved Runway Standards: A Discussion of Transport Canada’s 2012 Advisory Circulars.”
Since the material used to construct gravel runways is cheaper than materials used in paved runways, the initial investment is already substantially lower. The runways are also easier to maintain since damaged areas are typically isolated and can simply be re-grade.
Moreover, the maintenance itself requires markedly less equipment, according to a report on pavements and surface materials by Nonpoint Education for Municipal Officials. This makes it easy to ensure that remote communities can easily receive the supplies that they need without out too much capital investment.
Disadvantages
To be sure, gravel runways come with a unique set of challenges. The strength of these runways can vary dramatically and may be compromised, especially if not properly constructed or maintained. Spring thaws and moisture, poor drainage, and heavy use all impact the integrity of the runway and require targeted solutions.
According to Transport Canada, some factors like frost can lead to runway roughness, restriction of drainage, and a loss of soil strength. Coupled with heavy runway traffic, frost commonly results in ruts and depression, potholes, and soft spots. Luckily, these problems are all mitigated with simple re-grading.
In areas that experience permafrost, where the soil is frozen year round, it is vital to understand the active layer, or the upper layer of soil where thawing and refreezing takes place. Since most Arctic and Antarctic regions see very deep levels of active layer frost, made even deeper by runway construction, gravel pavements become the most advantageous because of their ease of repair. Importantly, maintenance issues can be significantly reduced with preservation techniques built into the runway itself.
The Best Problem is No Problem
Because of the versatility of gravel runways, they are a top choice in small operations all over the world, especially in remote areas where larger scale construction projects are impossible. Their ubiquity in these areas makes properly understanding their advantages and limitations, as well the best ways to construct them, all the more important.
Midwest Industrial Supply, Inc.’s Fines Preservation™ Program binds the runway’s surface aggregate fines together, which means the fines are not lost as dust during airplane and vehicular traffic. This subsequently limits gravel loss and raises the California Bearing Ratio (CBR, a measure of strength) of the runway, thereby reducing the maintenance costs by 50 percent annually.
The pavement-like strength of Midwest’s EK35® and EnviroKleen® products is enhanced, rather than weakened, by traffic, and can save up to five cubic meters of dust per takeoff. Greater strength and less runoff means fewer depressions, ruts, and scars from braking.
The non-corrosive properties of EnviroKleen and EK35 have been certified by Boeing, the most stringent corrosion standard in the United States. They are effective on clay, sand, gravel, limestone, and most native soils, so they can go wherever you need to — just like the aircraft that take off from these often essential smaller airstrips.
(Main image credit: Daniel Villeneuve/flickr)