DUST CONTROL By WILLIAM T. SUNLEY, Engineer of Local Roads and Streets

The use of dust palliatives on gravel and crushed stone surfaced roads has been common practice for over sixty years. It has been estimated that a single vehicle traveling at thirty miles per hour down a mile of gravel road produces four and one half pounds of dust spreading it over a 1000 feet wide swath centered on the roadway.

Direct tangible benefits from dust control can be realised by local agencies in reduced maintenance costs. Some report a 25 to 75 percent reduction in blading costs and a reduction in needed replacement aggregate for the surface. On an untreated roadway, gravel loss on a mile of road carrying 250 vehicles per day is estimated to be about 300 tons per year.

Many intangible benefits result from dust control. While it is not possible to place a dollar value on them, many times they alone warrant the use of a dust palliative. The tangible or direct savings to a local agency are an added bonus. Some of the intangible benefits are: reduced vehicle accidents, reduced vehicle damage caused by flying gravel, higher quality of life and property values for those working and living next to a treated road, reduced cleaning costs, reduced dust-related health problems, reduced impact on dust sensitive vegetation, reduced sedimentation in water bodies and reduced complaints from the public.

Selected locations on a roadway may result in the most efficient use of dust control. Typical spot locations would be: residences, businesses, public use buildings, rest areas, parks, orchards and vineyards, stop signs, uncontrolled stop intersections, railroad crossings, passing zones and areas of high truck traffic.

To maximize benefits, dust palliatives should be applied as soon as practical after the spring thaw. All applications should be made when the roadway surface is damp to aid in workability and compaction. Application should be done when rain is not predicted for a few days to prevent washing away of the freshly applied dust palliative.

The most commonly used dust palliative is calcium chloride in solution applied at a rate of about 2 pounds of calcium chloride solids per square yard as outlined in Bureau of Local Roads and Streets Specification LR 651. A typical cost in 1991 was about $150 per ton furnished and applied. This translates to $0.15 per square yard for the 2 pounds.

An asphalt emulsion known as PEP or Penetrating Emulsion Prime is a well performing dust palliative. The materials specification is outlined in LR 713. Its furnished and applied costs is about $0.60 per gallon. this calculates to be about $0.21 per square yard when PEP is applied at 0.35 gallons per square yard.

A material now being used experimentally shows some promise. It is a by-product of paper manufacturing known as lignosulfonate. Cost information from one Illinois location of a 50% solution applied at 0.5 gallons per square yard was reported to be $0.17 per square yard.

This has been a brief review of typical dust control practices. Local agencies are cautioned to use materials, application rates and procedures that fit their particular situations. Some of the information used in this article was derived from a report entitled "Guidelines for Cost Effective Use and Application of Dust Palliatives" published in 1987 by the Road and Transportation Association of Canada. A summary of this report was published in the January, 1990 Public Works magazine. •

June 1992 / Illinois Municipal Review / Page 5