California Department of Transportation
 

Compost

Compost Blanket Photos

What is This Treatment?

Mulch-like blanket of medium-coarse stable and mature compost, typically 2" thick. Note that compost blanket is a coarse woody product, not the fine, screened compost product typically used as a soil amendment.

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) - 1" maximum thickness.
    • Slopes 2:1 (H:V) - 2" maximum thickness.
    • Slopes 3:1 (H:V) - 3" maximum thickness.
    • Slopes 4:1 (H:V) - 4" maximum thickness.

Benefits:

  • Improved protection from raindrop splash erosion.

  • Reduced competition from weed species.

  • Reduced stormwater runoff volume and velocity.

  • Improved infiltration rate.

  • Conserves soil moisture.
  • 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:

  • Requires temporary storage space within the project limits to stockpile materials.
  • Applying high levels of organic materials may not be appropriate in arid regions of the state.

Technical Considerations

  • Compost can be blown on a site together with seed in a single-step, cost effective erosion control treatment.
  • Compost can also be blown in place together with a tackifier to help hold the material in place on steeper slopes.
  • Medium coarse compost has a a sieve size of greater than 1/2" and less than 3" in length. See specification for detailed dimensions.
  • Caltrans compost suppliers must be participants in the United States Composting Council's (USCC) Seal of Testing Assurance (STA) program. A list of current STA program participants is available at: US Composting Council (USCC) Seal of Testing Assurance (STA) Program Participants

Specifications:

Compost Calculator

Depth Enter design depth.
Area (SF) Enter area in square feet. For example 1 acre = 43560 square feet.
   
Cubic Yards  
Cubic Feet  

Common Compost Application Rates

Compost Depth Cubic Yards/Acre Pounds/Acre Tons/Acre
1/2" 68.5 54,800 27
1" 135 108,000 54
2" 270 216,000 108
3" 405 324,000 162

Average Compost Weight = 800 lbs/cubic yard (1050 lbs/cubic meter).

Compost Application Methods

Pneumatic Blower Truck

The large quantities of compost required for a compost blanket can be applied to a flat project site using a dump truck and a bulldozer. Projects with steep slopes, or areas inaccessible by vehicles require alternate methods - the most common method being a pneumatic blower truck.

Working like a vacuum cleaner stuck in reverse, a pneumatic blower truck can rapidly applies compost to steep slopes or constrained areas that are unreachable by traditional equipment. A 40 cubic yard blower truck holds roughly 35 cubic yards of compost, and applies this material at a rate of about 35 cubic yards/hour. A single truck should be able to apply a 1" thick compost blanket over a 2-acre site (280 CY total) in a single working day. The typical truck has a hose that can reach 300 feet - defining the farthest extents of application from the roadway. A rough estimate of cost for labor and materials for this work would run from $5,000 - $8,000 per acre. This price estimate does not include seed.

Consider Using With:

Combine with other Rolled Erosion Control Products to hold compost in place on slopes steeper than 2:1 (H:V).

To effectively treat sites with compacted, sterile or poorly draining soils, consider combining this treatment with

Plans and Details:

Estimate Information:

Research:

Model Guided Specification for Using Compost to Promote Establishment of Vegetation and Stormwater Quality Improvements, 2010

This study establishes parameters for compost use based on performance criteria including soil type, climate, slope length and steepness, aspect, and location. The research addresses how compost affects water quality and erosion, and if compost improves the establishment of permanent vegetation cover.

Regeneration of Nitrogen Fertility in Disturbed Soils Using Compost
Graphs nitrogen release from various composts and compares compost release rates with two native topsoils.

 

External Links:

Updated 03-19-2014