Biosolids laws, rules, and support documents

We oversee Washington's biosolids laws and the administrative rules, and provide support documents.

Laws & rules

Chapter 70A.226 RCW – Governing biosolids state law
Chapter 173-308 WAC – Rules for implementing the state biosolids program 

Statewide general biosolids permit

Statewide General Permit for Biosolids Management (expired) – This statewide permit applies to all facilities subject to the Washington's biosolids program. When facilities receive final approval of coverage, Ecology may impose additional or more stringent requirements based on specific circumstances of the proposal.

Draft Statewide General Permit for Biosolids Management – Currently in development.


Biosolids Management Guidelines – This guidance document helps biosolids managers and agency staff make appropriate decisions when evaluating site and facility proposals.

Managing Nitrogen from Biosolids – Nitrogen is a critical plant nutrient. This guidance document helps biosolids managers and staff understand how to evaluate nitrogen in biosolids.

Control of Pathogens and Vector Attraction Reduction in Sewage Sludge – This federal guidance document helps managers and staff understand the basis for pathogen reduction and controlling attraction to vectors in biosolids. This is the best guidance available for the purpose and there is no state equivalent.

40 CFR Part 503 - Standards for the Use or Disposal of Sewage Sludge – These are the federal rules on which the state program is based.

A Plain English Guide to the EPA Part 503 Biosolids Rule – EPA wrote this guidance document to help interested persons interpret requirements of the federal program. Washington’s program is based on the federal program.

Fertilizing with Biosolids – An excellent product of the joint efforts of Washington State and Oregon State Universities. It's published by Oregon State University Extension Service.

Other authoritative sources can inform decision-making

Other technical documents also inform decision-making. In particular, agronomic rates are often set using crop-specific nutrient management guidelines typically produced by university cooperative extension services.