Approved Compost and Bioretention Soil

The City of Seattle has mandatory specifications for soil, including compost and bioretention soil, for all City-funded projects within city limits. See section 9-14 of the City Standard Plans and Specifications.

Consistent with "closed-loop" theory and Resolutions 30990 and 31459 and the City's Sustainable Purchasing Policy, approved materials suppliers are those that have contracts to remove organic waste (feedstock or yard waste) from within the city of Seattle limits, compost the material and then resupply into City projects or sites.

As the resolutions are being applied, approved compost and bioretention soil vendors must:

  • Be under contract to remove food waste from the city limits (commercial or residential).
  • Hold a composting facility permit for feedstock processing and appear on the Washington Department of Ecology permitted facility list.
  • Be able to produce material test "slip" demonstrating the compost meets the specification requirements under 9-14.4(8), including 10 percent food waste.

The current list of permitted facilities contains contact and feedstock information for permitted compost facilities within our state for solid waste handling permits WAC 173-350-220(1) and (2).

Please contact City Purchasing and Contracting Services, for the current list of approved suppliers.