Wash. Rev. Code § 70A.205.205
After January 1, 1988, the department of ecology may prohibit disposal of sewage sludge or septic tank sludge (septage) in landfills for final disposal, except on a temporary, emergency basis, if the jurisdictional health department determines that a potentially unhealthful circumstance exists. Beneficial uses of sludge in landfill reclamation is acceptable utilization and not considered disposal.
The department of ecology shall adopt rules that provide exemptions from this section on a case-by-case basis. Exemptions shall be based on the economic infeasibility of using or disposing of the sludge material other than in a landfill.
The department of ecology, in conjunction with the department of health and the department of agriculture, shall adopt rules establishing labeling and notification requirements for sludge material sold commercially or given away to the public. The department shall specify mandatory wording for labels and notification to warn the public against improper use of the material.
RCW 70A.205.205