California Department of Transportation
 

Roadside Management Toolbox

Aggregate Base

Compacted Base Roadedge Compacted Base in Median

 

What is This Treatment?

This treatment consists of placing a compactable traffic bearing material such as Type 2 Aggregate Base, and compacting the material (90-95%) to prohibit root growth. Base material should be free of organic matter and other deleterious substances that support vegetation. This treatment should not consist of recycled asphalt or cement based materials.

When to use This Design Concept?

Compacted aggregate base is most appropriate as a vegetation control method in rural or natural areas and on low traffic volume facilities. This treatment may also be useful between the edge of pavement and a barrier treatment or as a temporary control where additional widening of the traveled way is imminent. Vehicle traffic on compacted material, especially during wet periods, may cause rutting and disturb vegetation control effectiveness. Use only in areas with good access for performing re-compaction on a regular basis.

Benefits:

  • Type 2 Aggregate Base is a commonly used construction material and readily available in most locales. Most contractors and Caltrans Maintenance crews have the equipment and construction knowledge for proper installation.
  • Material and placement will generally be less expensive than most other treatments.
  • Neutral color of aggregate base blends well with existing features.
  • Treatment is easy to remove if necessary for future projects and can be relocated to another location on the project.
  • Aggregate base, even when compacted, will retain a small amount of runoff through percolation.

Limitations:

  • Porous nature of treatment allows for greater weed germination than hard surface treatments.
  • Effectiveness is limited by the amount of disturbance once material is in place and other factors such as subgrade preparation, degree of compaction and weather conditions.
  • Spot application of herbicide and re-compaction of material may be necessary to extend treatment’s viability.
  • This treatment may have storm water implications in some areas.

Standard Specifications

  • 26-1.02 Class 2 Aggregate Base
  • 26-1.03 Subgrade
  • 26-1.035 Adding Water
  • 6-1.04 Spreading
  • 26-1.05 Compacting

Cost:

  • $10 - $30/yd2
  • BEES Item(s) - 260200 AGGREGATE BASE