California Department of Transportation
 

Local Topsoil

Topsoil

What is This Treatment?

Local topsoil is topsoil obtained from within the project limits and includes removing, stockpiling, and placing local topsoil on areas disturbed by construction activities.

Local topsoil is the one of the most effective methods to establish vigorous vegetative coverage because local topsoil typically contains the ideal physical, chemical and biological properties to establish vegetation.

Where to Use This Treatment:

  • Typically applied on slopes 1.5:1 (H:V) and flatter. The following application rates are suggested:
    • Slopes 1.5:1 (H:V) - 2" maximum thickness.
    • Slopes 2:1 (H:V) - 3" maximum thickness.
    • Slopes 3:1 (H:V) - 4" maximum thickness.
    • Slopes ≤ 4:1 (H:V) - 6" maximum thickness.
  • Caltrans Highway Design Manual Topics 110.2(2) and 110.2(4) recommend considering the use of Local Topsoil to treat disturbed soil areas to help protect stormwater runoff quality.

Benefits:

  • Reduced stormwater runoff volume and velocity.
  • Improved infiltration rate.

  • Improved soil water holding capacity.

  • Improved soil structural properties - soil structure, porosity, and texture.

  • Improved soil chemical properties - providing proper pH, carbon, nitrogen, potassium and phosphorus levels.

  • Improved soil biology - activity by bacteria, mycorrhizal fungi, nematodes, protozoa, microarthropod and earthworms.

  • Improved soil nutrient levels and nutrient cycling.

  • Improved potential for vigorous long term vegetation coverage.

Limitations:

  • More costly (yet more effective) than surficial treatments such as Erosion Control (Hydroseed).

  • Requires temporary storage space within the project limits to stockpile materials.

  • Requires removal of noxious weed species prior to harvesting of materials from the project site.

  • Requires site accessibility by earthwork equipment.

Specifications:

To specify the use of Local Topsoil, do the following:

  1. Read Standard Specifications Section 21-2.02C Topsoil. Local Topsoil is defined in Section 21-2.02C(2), and also directs you to Section 19-2.03D Selected Material, which defines Selected Material in Section 19-2.01B Definitions. Note that all the requirements in Section 19-2.03 Selected Material also apply to Local Topsoil.
  2. Because Local Topsoil is specified as "Selected Material", Local Topsoil is paid for as Roadway Excavation.
  3. Show the areas to be excavated and areas to be applied on the layout or grading plans.
  4. Include the bid item for Roadway Excavation in the Bid Item List.

Consider Using This Specification With:

To provide protection for the soil surface, consider combining this treatment with:

  • Hydroseed
  • Duff - a duff layer reduces raindrop impact erosion and serves as a source of native seed and mycorrhizal fungi.
  • Compost Blanket with seed applied at the same time.

Plans and Details:

  • There is no Standard Plan for Topsoil

Estimate Information:

  • No BEES Code for Local Topsoil, but please see below.
  • Local Topsoil should be specified as Selected Material.
  • Per Caltrans Standard Specifications Section 19-2, Selected Material is paid for as Roadway Excavation. Use the Bid Item for Roadway Excavation: 190101

Guidance:

External Links:

Updated 04-13-2016