King County produces a lot of crap. After passage and break down through sewer treatment plants in Seattle some of the remaining dry solids are shipped across the mountains to Douglas County dryland farms on the Waterville Plateau.
The nearly black biosolids stand in sharp contrast to the light brown native glacial soils.
Dryland farms in Douglas County have been receiving biosolids from King County for over 20 years.
The product is regulated by both Washington State and the EPA with metals being one of the primary concerns. The King County product is very low in metals, and adds nutrients and structure to the soil.
The Boulder Park Project on numerous dryland wheat farms in Douglas County receives about 60% of the biosolids from King County or 68,000 tons. The name Boulder Park is derived from the many large boulders on the glacial drift plains of the Waterville Plateau.