Dust prevention on gravel roads is a problem that is as old as the roads themselves. Not only is dust a nuisance to breathe, but it can settle on houses, cars and outbuildings, and be a real mess to clean up.
In pursuit of dust control, there are a couple of tried and true methods and some more modern approaches that may work as well as, or better than, anything that has been done before.
Oil and Water
The two most common ways to prevent dust is to spray the road with either oil or water.
Spraying a gravel road with water will undoubtedly keep the dust down as long as the road stays wet. However, on dry hot summer days, keeping the road wet enough to maintain dust control would be a full-time endeavor. A sprinkler system would need to be used that would waste hundreds of gallons of water, and would therefore not be a practical solution.
Spraying roads with oil is a much more workable proposition. Oil remains active for much longer periods of time, quite possibly for an entire summer. The huge drawback is the environmental ramifications of spraying petroleum-based oil products into the environment. Rain runoff can pollute ponds and destroy plants growing next to the road, and because of these environmental concerns, many communities around the U.S. have banned oil spraying altogether.
Calcium chloride and lignin sulfonate, two salts, when mixed with water in about a 35 percent solution and sprayed over gravel roads, have been found to be very effective at keeping dust down.
These salts attract water from the air, keeping the roadway slightly moist at all times, and thereby capturing dust in the process. You may want to call up your local farm and implement store to find out about cost and availability.
Soybean Oil Soapstock
A byproduct of soybean oil called called soybean oil soapstock, which is a common base oil for natural soaps, can be used in its liquid state and sprayed onto roads as a very environmentally friendly way to prevent dust. Coverage is about 1/4 of a gallon per square yard of roadway and has been proven at this rate of application to last all summer.
It does not pollute waterways during runoff and is considered non-toxic for plants and animals. It should be sprayed onto roadways as is, and it is never to be mixed in a water solution. Ideally, the ambient air temperature should be at least 75 degrees. Faster and better penetration into the gravel will occur with higher temperatures.