Gravel Road Maintenance
The Department of Public Works Operations is responsible for the maintenance of approximately 592 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 motor grader 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 frequency 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 rain.
Over time, the aggregate 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 7-10 years.
Douglas County performs dust mitigation on approximately 152 miles of gravel roads each year. Population growth has increased vehicular traffic on gravel roadways resulting in increased fugitive dust. Douglas County mitigates dust to:
- Comply with State of Colorado Air Quaility Control Commission regulations and State of Colorado Regulation 1 and PM10 (particulate matter < 10 microns) standards established to reduce dust from gravel roads with traffic counts over 200 vehicles per day
- Resident health concerns
- Decrease the amount of routine maintenance required
- Improve sight distance with dust reduction
Douglas County currently uses two application processes to mitigate dust. Both processes involve the application of a suppression material containing magnesium chloride as 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 complex sugars. Complex sugars 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 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 using a topical product called Durablend as manufactured by Envirotech Services, Inc. who states that this proprietary product contains magnesium chloride with polymers that have been formulated to reduce the amount of magnesium chloride that leaches into the environment.
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
- Douglas County Policy on County Assisted Paving Project (CAPP) Gravel Road Paving Assistance
- Local Improvement Districts (LID) Gravel Road Paving and Other Infrastructure Construction
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 1990s in order to meet Regulation 1 requirements.
How can I get a 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.