The purpose of this document is to define the policy for the application of dust control palliatives to granular surfaced secondary roads under the jurisdiction of the Johnson County Secondary Road Department. It is the policy of Johnson County to allow the application of dust palliatives by property owners and tenants living adjacent to county unpaved roads for the control of dust. On more heavily traveled roads, the county recognizes that the control of fugitive dust generated by greater traffic is a safety concern. This policy defines the County’s Safety Program for Dust Control.

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  1. Average Daily Traffic (ADT): Average daily traffic is the average traffic count on any road based on 365 day per year use. Average daily traffic counts are based on the official counts conducted every four years by the Iowa Department of Transportation (IDOT).
  2. Fugitive Dust: Fugitive dust is defined by Iowa Administrative Code section 567-20.2(455B) as any airborne solid particulate matter emitted from any source other than a flue or stack. By IAC 567-23.3(455B)c(1), farming operations and dust generated by ordinary travel on unpaved roads is not considered to be fugitive dust.
  3. Peak traffic count: Peak traffic count is a maximum or above average traffic count based upon a one-time traffic count. Peak traffic counts differ from average daily traffic since they may be taken at the time of a special event or a temporary increase in road use. Short term increases in road use may be due seasonal farm operations such as planting and harvest, temporary construction traffic, special events such as farm sales, weddings or parties, use of a road as a haul road or detour route, and other one time or short duration uses. Peak traffic counts are not used for the purpose of determining eligibility for the county safety program.


County Safety Program for Dust Control

For the purposes of this program, traffic exceeding 150 vehicles per day (vpd) average daily traffic (ADT) on roads with a speed limit greater than 25 mph are considered to have a traffic volume sufficient to require application of dust control by the county to promote safer road usage. It is the intent of this section to establish public policy and provide a coherent and equitable method of determining the extent to which the county will treat its granular surfaced roadways to limit dust. It is not the intent of this program to define normal traffic as less than 150 vpd, or fugitive dust generation at traffic volumes above 150 vpd.

The determination of average daily traffic count is based on the most recent Iowa Department of Transportation traffic survey for Johnson County. During the course of a year, counts may peak due to one time or annual events such as farm sales, fairs, parties, or seasonal activities, and may lull due to temporary road closures for construction or due to bridge postings. Peak counts will not be used for the determination of the road segment’s qualification for dust control. With the exception of parks and recreational areas as recommended annually by the County Engineer and approved by the Board of Supervisors, only average daily traffic in excess of the 150 vpd count will be dust treated by the county under this safety program. Special traffic counts may be done as directed by the County Engineer in cases where conditions on roads have changed due to the use of the road as an unofficial construction detour or haul route, the development of new subdivisions or industrial sites, or other special conditions. In these cases, since long term traffic patterns and average volumes cannot be established by short-term counts, the minimum traffic count necessary for inclusion in the safety program is 200 vpd.

The county will use calcium chloride for treatment of roads within the safety program. These roads will be treated with at least one-single application annually. Treated roads will be maintained and bladed as determined necessary by county maintenance forces. If private residents wish to treat over the chloride treated areas with other approved products, they may do so at their own risk and expense. The County Engineer does not recommend that residents treat chloride treated areas with other products such as lignon sulfonate and MC-70. These coatings may not hold up well when applied on top of chloride. If the areas treated with MC-70 or lignon sulfonate over the county applied chloride fail or begin to pothole, the county may repair the damaged area in the course of normal road maintenance without notice or compensation to the permittee. Repair by the county will consist of scarifying the treated area and maintaining it as a granular surfaced road.

Dust palliative will normally by applied at those sections of the road where control of dust will enhance traffic safety, i.e.: at intersections, at bridges, at sharp horizontal curves, at vertical curves with limited sight distance, house driveways, and at other locations determined by the County Engineer. Only when determined necessary by the County Engineer will palliative be applied on the
entire route. Residents may extend treated areas at their own expense by applying for a permit from the county and paying the appropriate cost of the material.

Note: Johnson County will use calcium chloride as the dust palliative for roads treated under the safety program. MC-70, which has replaced waste and crankcase oil as an available bituminous (blacktop) product due to changes in federal regulations governing the use of waste oils, is more costly for the county. Calcium chloride allows efficient, routine maintenance without damage to the dust palliative properties of the material.


Park and Recreational Roads

Johnson County will treat granular surfaced roads to county park entrances, state park entrances, golf courses and other recreational sites as established annually by the County Board of Supervisors. These roads will be treated with calcium chloride and maintained as determined by county maintenance forces.


Quarry Roads

Johnson County will negotiate with quarry operators to pay a share of the cost to dust treat roads leading from active quarry sites located on granular surfaced roads. The county will select the most reasonable route to provide access to the quarry. The county will treat the selected route at bridges, at intersections, at sharp horizontal curves, and over hills with limited sight distance from the quarry entrance to a paved road. Homes and businesses along the selected route will receive 500 lineal feet of dust control free of charge. The owner or resident may purchase additional dust control.


Construction Detours and Haul Roads

Dust palliatives will be applied to granular surfaced roads established as official detours or haul roads by Johnson County for a county construction project. Roads temporarily closed for construction that have a traffic count greater than 200 vpd may have an established detour which will be treated with calcium chloride under the same guidelines as the county safety program. The application of dust palliatives on official detours and haul roads will be at county expense. Residents may extend treated areas on detour routes at their own expense by applying for a permit from the county and paying the appropriate cost of the material.

Traffic dislocation caused by another governmental jurisdiction’s construction activities (cities, neighboring counties, or Iowa Department of Transportation (IDOT) shall be measured by the Johnson County Secondary Road Department upon receipt of a complaint by a county resident along an affected road. If the traffic count taken upon request is above 250 vpd, the road will either by treated as a construction detour and the county will apply calcium chloride as a dust palliative, or other remedies will be applied to reduce traffic to normal levels at the option of the County Engineer.

County granular surfaced roads designated by IDOT as temporary primary haul roads for state highway department construction work will be treated in the same manner as county safety program roads. Applications of dust palliatives will be placed according to county standards included as appendix C of this policy. The IDOT will maintain roads designated as temporary primary haul roads. Dust palliatives will be paid for by IDOT and road use will be managed by IDOT.

Appendix C

Safety and detour route dust palliative application guidelines

When treating roads on the safety program or on construction detours and haul roads, the county will use the following guidelines for application of dust palliative:

500 feet both directions on the designated route shall be treated.

House Driveways
500 feet total, 250 feet each side of the driveway.

Bridges, culverts, and approach guardrail
Dust palliative shall be applied between 100 and 150 feet in advance of the end of the bridge barrier rail depending upon the width and geometry of the bridge. Dust palliative shall be applied for 150 feet with the treated area centered on the culvert. Culverts narrower than road top width may have the treated area extended as directed by the engineer.

Hills and curves
Areas shall be treated as directed by the County Engineer.

Gaps between treated areas
Gaps up to 150 feet near home sites shall be treated with dust palliative.