Gravel Road Maintenance
The Department of Public Works Operations is responsible for the maintenance of approximately 300 center lane miles of gravel roadways within Douglas County. These roadways range from rural collectors with several hundred vehicles per day from neighborhoods to local roads that carry less than 20 vehicles per day. Due to the nature of gravel roads, periodic routine maintenance is performed to retain a surface that is safe to travel. There are several factors that determine the level of maintenance required on a gravel road:
- Quality of gravel surface
- Speed of traffic
- Volume of traffic
- Weather conditions
A motorgrader is used to maintain the surface of a gravel road. It can cut out surface irregularities such as washboards, potholes and ruts to improve driver safety. Washboards and potholes typically form on hills, curves, flat areas and near stop signs where vehicle braking occurs. Traffic and speed impact the frequently and severity of washboards formation.
In order to cut the compacted gravel to a sufficient depth to remove surface irregularities moisture is required. To get adequate moisture for proper compaction and a tight surface, water is frequently applied using tankers with spray bars. Roads are frequently bladed after a rain.
Over time, the aggregrate surface on gravel roads is lost from deterioration due to vehicle traffic and the effects of weather. When the stability of a gravel surface has substantially deteriorated, new gravel is applied to the road. The average interval between new gravel applications varies based upon traffic volume and other factors, but is normally performed every 5-7 years.
Douglas County performs dust mitigation on approximately 80 center lane miles of gravel roads each year. Some of the reasons for the application of dust mitigation products are:
- To comply with State of Colorado Regulation 1 that requires the mitigation of dust on Douglas County gravel roads with average daily traffic volumes exceeding 200 vehicles per day
- Mitigate dust due to resident health concerns
- Decrease the amount of routine maintenance required
- Reduction of dust to improve sight distance
Processes and products used for dust suppression
Douglas County currently uses two application processes to mitigate dust. Both processes involve the application of a suppression material containing magnesium chloride. The two processes are described below:
Soil Stabilization Method
The majority of dust suppression performed in Douglas County is done through the use of a soil stabilizer. A soil stabilizer is used to evenly distribute the liquid dust suppression material into the top 3 inches of the gravel surface. This method requires additional equipment to grade the road and compact the 3 inches of disturbed gravel.
The dust suppression material currently being used in conjunction with this process consists of a 70/30 blend of magnesium chloride and lignin sultanate. Lignin sulfonate is typically derived from the processing of wood and paper products. This method is typically used on roads that carry higher volumes of traffic because the 3 inch depth of stabilization will typically retain a longer-lasting surface integrity.
Topical Application Method
A topical surface treatment is placed on gravel roads that have lower volumes of traffic. The topical method is faster than the soil stabilizer method, however, the liquid dust suppressant only penetrates approximately ¼ inch below the gravel surface.
Douglas County is currently testing a topical product called Durablend as manufactured by Envirotech Services, Inc. who states that this proprietary product contains magnesium chloride with polymers that has been formulated to reduce the amount of magnesium chloride that leaches into the environment and that can affect the health of roadside vegetation. Douglas County is currently conducting chloride testing on roadside vegetation to determine the product effectiveness.
Paving Gravel Roads
A large number of residential streets were not required to be paved at the time the subdivision was approved. There are roughly 135 miles of County-maintained residential, gravel roads within 34 subdivisions. There are also many miles of private gravel roads, not maintained by the County. Some residents within these subdivisions have expressed a desire to have these roads paved. The County has developed two options for residents in subdivisions with gravel roads.
Programs Available to Get Gravel Roads Paved
For more information regarding:
Local Improvement Districts (LID), please contact the Engineering Department at 303.660.7490.
County Assisted Paving Project (CAPP), please contact the Road & Bridge Department at 303.660.7480.
Frequently Asked Questions
What is the purpose of dust suppression?
The State of Colorado Department of Public Health and Environment enacted Regulation 1 which requires the mitigation of dust particulates on roadways with an average of traffic volumes exceeding 200 vehicles per day. The County started treating several roadways in the 1990’s in order to meet Regulation 1 requirements.
How can I get dust suppressant applied to the road that I live on?
The County applies dust suppressant material to gravel roads as budget allows. The budget for dust suppression allows for the treatment of heavily traveled gravel roads and a limited number of residential roadways. The County may require financial participation from residents for the cost of the dust suppression material if the dust suppression budget is not adequate for additional roadway requests.
Residents wanting dust suppressant material applied to their roadway can contact Public Works Operations at 303.660.7480.