What does clean dirt or soil mean?

We abide by the Washington State Legislation rules and definition of Clean soil: WAC 173-350-100

Clean soil

Clean soil means soil does not contain contaminants from a release. It also includes soil that contains one or more contaminants from a release and when moved from one location to another for placement on or into the ground:
(a) Does not contain contaminants at concentrations that exceed a cleanup level under chapter 173-340 WAC, Model Toxics Control ActCleanup, that would be established for existing land use at the location where soil is placed; or
(b) Contains contaminants that affect pH, but pH of the soil is between 4.5 and 9.5 or within natural background pH limits that exist at the location where soil is placed.
Examples of potentially clean soil may include, but are not limited to:
  • Soil from undeveloped lands unlikely to have impacts from release of contaminants associated with area-wide or local industrial or historical activities.
  • This includes similar soils over which development may have occurred but land use is unlikely to have led to a release, such as use for residential housing, or over which development provided protection from impacts from a release, such as coverage by pavement.
  • Soil with substances from natural background conditions, as natural background is defined in WAC 173-350-100, is clean soil under this section.