King County Environmental Purchasing Program

Compost as Organic Soil Amendment

• Introduction
• Usage History and Experience
• Bid and Contract Specifications
  • Compost, Washington State Department of Transportation
  • Compost Amended Topsoil, King County Road's Division Contract
  • Compost Amended Topsoil, King County Factoria Transfer/Recycling Station
  • Organic Amendment, Regional Justice Center Project
  • Organic Amendment and Forest Mulch, Metro West Point Project
  • Planting Soil, City of Seattle Specification
• Product Experience
  • Compost-Amended Topsoil at the West Point Treatment Plant
• For More Information
• Vendor Information

Introduction

When topsoils are being prepared for planting landscape areas, they are often amended with an organic material to create optimum conditions for plant growth. Compost is produced from organic municipal waste materials and can be used as an organic amendment for topsoils.

Usage History and Experience

Compost‑amended topsoil is specified for use in maintenance and construction projects. The Roads Environmental Unit reported that in the past year, their contractors used almost 4,000 cubic yards of topsoil containing primarily yard waste compost, with about ten percent containing biosolids compost.

Bid and Contract Specifications
King County agencies purchase compost and compost-amended topsoil through term-contracts with local vendors. This section includes specifications from King County, City of Seattle and Washington State.

Washington State Department of Transportation
2006 Standard Specifications for Road, Bridge, and Municipal Construction

9-14.4(8) Compost

Compost products shall be the result of the biological degradation and transformation of plant-derived materials under controlled conditions designed to promote aerobic decomposition. Compost shall be stable with regard to oxygen consumption and carbon dioxide generation. Compost shall be mature with regard to its suitability for serving as a soil amendment or an erosion control BMP as defined below. The compost shall have a moisture content that has no visible free water or dust produced when handling the material.

Compost production quality shall comply with Chapter 173-350 WAC.

Compost products shall meet the following physical criteria:

1. Compost material shall be tested in accordance with the U.S. Composting Council, Testing Methods for the Examination of Compost and Composting (TMECC) Test Method 02-02-B, "Sample Sieving for Aggregate Size Classification."

Fine Compost shall meet the following:

	Min.	Max.
Percent passing 2"	100%
Percent passing 1"	90%	100%
Percent passing 3/4"	70%	100%
Percent passing 1/4"	40%	75%

Maximum particle length of 6-inches

Coarse Compost shall meet the following:

	Min.	Max.
Percent passing 3"	100%
Percent passing 1"	90%	100%
Percent passing 3/4"	70%	100%
Percent passing 1/4"	40%	75%

Maximum particle length of 6-inches

2. The pH shall be between 6.0 and 8.5 when testing in accordance with TMECC 04.11-A, "1:5 Slurry pH".

3. Manufactured inert material (plastic, concrete, ceramics, metal, etc.) shall be less than .5 percent on a dry weight or volume basis, whichever provides for the least amount of foreign material.

4. Minimum organic matter shall be 40 percent dry weight basis as determined by TMECC 05.07A, "Loss-On-Ignition Organic Matter Method".

5. Soluble salt contents shall be less than 6.0 mmhos/cm tested in accordance with TMECC 04.10-A, "1:5 Slurry Method, Mass Basis".

6. Maturity greater than 80%in accordance with TMECC 05.05A, "Germination and Root Elongation".

7. Stability 8 or below in accordance with TMECC 05.08-B, Carbon Dioxide Evolution Rate".

8. The compost product must orininate a minimum of 65 percent by volume from recycled plant waste as defined in WAC 173-350 as "Type 1 Feedstocks." A maximum of 35 percent by volume of other approved organic waste and/or biosolids may be substituted for recycled plant waste. The supplier shall provide written verification of feedstock sources.

The compost supplier will test all compost products within 30 calendar days prior to initial application with samples taken from the material stockpiled by the supplier for project use. Samples will be taken using the Seal of Testing Assurance (STA)sample collection protocol. (The sample collection protocol can be obtained from the U.S. Composting Council, 4250 Veterans Memorial Highway, Suite 275, Holbrook, NY 11741 Phone: 631-737-4931). The sample shall be sent to an independent STA Program approved lab. The compost supplier will pay for the test. A copy of the approved independent STA Program laboratory test report shall be submitted to the Contracting Agency prior to initial application of the compost.

Compost not conforming to the above requirements or taken from a source other than those tested and accepted shall be immediately removed from the project and replaced at no cost to the Contracting Agency.

The contractor shall either select a compost supplier from the Qualified Products List, or submit the following information to the Engineer for approval:

1. A Request for Approval of Material Source.

2. A copy of the Solid Waste Handling Permit issued to the supplier by the Jurisdictional Health Department as per WAC 173-304 (Minimum Functional Standards for Solid Waste Handling).

3. The supplier shall verify in writing, and provide lab analyses that the material complies with the processes, testing, and standards specified in WAC 173-350 and these specifications. The analysis shall be performed by an independent STA Program certified laboratory.

4. A list of the feedstock by percentage present in the final compost product.

5. A copy of the producers Seal of Testing Assurance certification as issued by the U.S. Composting Council.

Acceptance will be based upon a satisfactory Test Report from an independent STA program certified laboratory.

Compost-Amended Topsoil, King County Roads Division Contract

Compost-amended Topsoil shall be a commercially manufactured mixture of soil and pure compost which meets the physical and chemical requirements for Type A topsoil in accordance with Standard Specifications 9.14.1 (1) (see above WSDOT specification) except that the total organic matter content shall be 15% to 30%. The compost used in the mixture shall consist of a well-decomposed, humus-like material derived from composting of yard waste, biosolids, or well-rotted manure with a minimum of litter (straw, sawdust, or shavings). The organic material shall contain no plastic, concrete, glass, tree or shrub branches, or fresh, or partially decomposed wood by-products or similar material. Compost containing yard waste or biosolids shall be produced at a facility possessing a valid Solid Waste Composting Permit issued by the jurisdictional Health Department.

Compost Content:

Compost shall contain no plastic, concrete, glass, tree or shrub branches, fresh or partially decomposed wood by-products or similar material.  Compost containing yard waste or biosolids shall be produced at a facility possessing a valid Solid Waste Composting Permit issued by the jurisdictional Health Department.

Bidder shall indicate the source of feedstocks for each compost type offered (such as yard waste; yard waste and dairy cow manure with bedding; biosolids and yard waste, etc.)

 

Compost Amended Topsoil, King County Factoria Transfer/Recycling Station

Section 02900- Planting

PART 2 PRODUCTS - Excerpts

2.01 TOPSOIL (PLANTING SOIL)

A. General: Topsoil to be fertile, friable, sandy loam, and to supply the following composition requirements: weed and seed free; pH between 5.5 and 7.5; maximum particle size to be 1/2 inch, with 97% to I 00% passing the 3/8" screen; maximum electrical conductivity shall be 2.0 milliohms; maximum exchangeable sodium shall be 10%; free of clay lumps, litter, and toxic matter harmful to plant growth. Pure organic content of topsoil mixture shall be 30% maximum and 1 0% minimum. Topsoil components shall be 35% sand, 40% composted yard waste and 25% sandy loam, components shall conform to the requirements indicated. Mixing of the soil components shall not occur on site.

C. Composted Yard Waste:

1 . Material derived from aerobic decomposition of recycled plant

waste fully composted for a minimum of 6 months between 131 F and 165 F; materials shall have a moisture content such that no visible free water or dust is produced when added after the composting process has begun. Yard waste shall be from a permitted composting facility. Cedar Grove or approved alternate.

2. Submittals: Submit the following for approval prior to mixing: composted yard waste sample, b) a copy of the Solid Waste Handling Permit issued to the supplier by the Jurisdictional Health Department.

Organic Amendment, Regional Justice Center Project

2.04 Organic Amendment

A. Soil amendment shall consist of a commercially prepared

compost product which is a Washington State Classified "Recycled Content Product" manufactured at a permitted facility that meets the minimum standards established by Washington State Department of Ecology as defined in WAC 173-304-300 and 400. Compost may be made by composting yard waste with biosolids per EPA/40 CFR Part 503 regulations of February 1993. The mixed soil shall be screened through a 3/8-inch screen and have a pH of 5.5 - 7.

B. Compost products shall contain composted plant waste

material derived from the aerobic decomposition of recycled plant waste. The composted plant waste shall have a moisture content that has no visible free water or dust produced when handling the material.

C. Compost products shall meet following physical criteria:

 

100 percent shall pass through a 1-inch sieve when tested in accordance with WSDOT Test Method 602 and 603 (AASHTO T87 and T88).

The pH range shall be between 5.0 and 8.5 when tested in accordance with WSDOT Test Method 417.

Foreign material (plastic, mineral soils, concrete, metal, etc.) shall not be more than 2 percent on a dry weight or volume basis, whichever provides for the least amount of foreign material.

D. Acceptance of composted products shall be based on the following submittals by the Contractor:

A Request for Approval of Material Source.

 

A copy of the Solid Waste Handling Permit issued to the supplier by the Jurisdictional Health Department as per WAC 173-304 (the Minimum Functional Standards).

 

Certification by the suppler that the compost products originate 100 percent from recycled plant waste. A maximum of 35 percent by volume of other approved organic waste and/or biosolids may be included. They shall conform to the physical criteria listed above and be listed by percentage of the final compost product.
Contact the Regional Justice Center Office at (206)296-1707, for more information about this project.

Organic Amendment - West Point Project

Compost was specified by the West Point waste-water treatment project, which used 40,000 cubic yards of topsoil amended with biosolids compost.

Topsoil Type A, Upland Topsoil shall be an imported material, manufactured and stored offsite, consisting of a homogenous mix of organic amendments, granular soil and, where indicated, limestone as specified herein. Topsoil shall be free of objects larger than 1-inch in diameter, toxic substances, and any other deleterious materials which may be harmful to grading, planting, plant growth, and maintenance operations. Topsoil shall meet the following requirements:

1. Organic amendments

A. The organic amendment for Type A Upland Topsoil shall be a blended mix of 3 parts hemlock and/or fir dust and 1 part digested biosolids. The mix shall be composted for a minimum of 1 year.

B. Gradation of the organic amendment shall be as follows:

Sieve Size	Percent Passing
1/2 inch	99
1/4 inch	90
No. 8	50
No. 18	10
No. 35	1

 

C. The organic amendment shall be "GROCO', as supplied by Sawdust Supply Co, Inc, Seattle, WA or approved equal.

 

2. Granular Soil

 

A. The granular soil component of Type A, Upland Topsoil, before the addition of organic amendments shall be a material conforming to the following gradation:

Sieve Size	Percent Passing
1/4 inch	100
No. 4	97-100
No. 10	85-95
No. 30	65-80
No. 50	15-30
No. 100	0-3

B. The organic amendments component of Type A, Upland Topsoil, shall be thoroughly incorporated into the granular soil at the rate of 40 percent by volume. The Contractor shall submit a description of its quality control procedures to achieve the specified material blending.

 

3. Forest Mulch
Note: Recycled wood mulch was substituted in this project.

A. General: Forest mulch shall be a compost product that is a well decomposed material derived from the aerobic decomposition of organic, recycled, plant waste. The compost shall have an earthy odor, shall be free of viable weed seeds, plant propagules, and plant pathogens, and shall have a moisture content such that no viable free water or dust is produced when handling the material. The compost shall be visually free of identifiable grass or leaf fragments upon close inspection of the pile.

B. Forest mulch shall meet the following physical and chemical criteria:

1. 100 percent shall pass through a 1-inch sieve.

2. The pH shall be between 5.5 and 7.5

3. The material shall be visually free of manufactured inerts such as glass, metal, and plastic, or identifiable grass or leaf fragments.

4. The organic matter content shall be 30 percent minimum, by dry weight.

5. The material shall have a maximum electrical conductivity of 5 mmhos/cm.

6. The nitrogen content shall be a minimum of 0.25 percent.

C. No fresh sawdust or other fresh wood by-products shall be added to extend the volume after the composting process.

D. Forest mulch shall comply with all applicable public health standards and be obtained from a compost facility that holds a solid-waste handling permit from the health department with jurisdiction.

E. Acceptance of forest mulch shall be based upon approval of submittals supplied by the Contractor as specified in paragraph 1.3B of this section. Once submitted material has been approved, the Contractor shall quarantine compost material at the vendor's plant, or take other steps as necessary to ensure that tested materials is the material shipped to the construction site.

 

4. Submittal A minimum of 90 days prior to intended date of shipment of forest mulch to the construction site, the Contractor shall submit the following for each 1,000 cubic yards to be shipped:

A. Test results showing total and available macro and micro nutrients, sodium, pH, salinity, moisture content, bulk density, organic percent, particle sizes, and estimated carbon:nitrogen ratio, as well as agricultural suitability test to encompass sodium absorption ratio and boron saturation extract.

B. Bioassay results to evaluate potential organic compound phytotoxicity.

C. Two-gallon sample for visual analysis.

For more information, please contact Linda Sullivan, Landscape Manager, West Point Project (206)263-3322 or look to Compost-Amended Topsoil at West Point Treatment Plant and recycled wood mulch

Planting Soil, City of Seattle Specification

Planting soil shall consist of 2/3 soil and 1/3 organic material by volume.

A. The soil shall meet the following requirements:

Soil shall be sandy loam or loamy sand consisting largely of sand, but with enough silt and clay to give it a small amount of stability. Individual sand grains can be seen and felt readily. On squeezing in the hand when dry, it shall fall apart when the pressure is released; on squeezing when moist, it shall form a cast that will not only hold its shape when moist, but will hold its shape when the pressure is released, and shall withstand careful handling without breaking.

The mixed soil shall meet the following:

Size	Sieve	Percent Passing
3/8"	ASTM E-11	100
#10	ASTM E-11	85-100
#270	ASTM E-11	10-50
.002 mm	Clay	0-10

 

B. Shall have a ph range of 5.0 - 6.5 with dolomitic limestone added as necessary to

attain this range.

C. Organic material shall consist of composted yard debris or organic waste material

and shall consist of 100% recycled content.
In addition, the organic material shall have the following physical characteristics:

1. Shall be screened using a sieve no finer than 7/16" and no greater than 3/4".
   
2. Shall pass a standard cress test for seed germination (90% germination compared to standard).
   
3. Shall have a pH from 5.5 to 7.5.
   
4. Shall contain at least 25% organic matter by dry weight.
   
5. Shall have a maximum electrical conductivity of 3.0 mhos/cm.
   
6. Shall have a maximum carbon to nitrogen ratio of 40:1.
   
7. Shall be certified by the Process to Further Reduce Pathogens (PFRP) guideline for hot composting as established by the United States Environmental Protection Agency.

D. Submit soil analysis from a soils testing laboratory to the Engineer.

Indicate source and obtain the Engineer's approval before hauling to site (analysis test with a two (2) pound bag sample is required.)

For More Information

Further information may be available through the following main menu selections:

King County Recycled Content Supply Contracts
Resources for Buyers
Standard Paragraphs for Contracts
Compost-Amended Topsoil at West Point Treatment Plant

Vendor Information

Partial list of King County contractors, who supply compost:

Cedar Grove Compost, Maple Valley, WA (425)763-2700
Sawdust Supply, Kent, WA (253)622-4321
Pacific Topsoil, Bothell, WA (425)337-2700
Northwest Cascade, Puyallup, WA (253)848-2371
Lloyd Enterprises, Federal Way, WA (253)874-7792

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Updated: May, 2007

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