(1) These rules apply to all treatment works treating domestic sewage as defined by this chapter. In addition, these rules apply to, but are not limited to, the following:

(a) A person who prepares biosolids or sewage sludge.

(b) A person who stores biosolids or sewage sludge.

(c) A person who applies biosolids to the land.

(d) Biosolids that are applied to the land.

(e) The land where biosolids are applied.

(f) The owner and lease-holder of land where biosolids are applied.

(g) A person who disposes of sewage sludge in a municipal solid waste landfill.

(h) Sewage sludge that is disposed of in a municipal solid waste landfill.

(i) Biosolids or sewage sludge generated at an industrial facility during the treatment of only domestic sewage.

(j) A person who transfers biosolids or sewage sludge from one facility to another.

(k) A person who transports biosolids or sewage sludge.

(l) Mixtures of biosolids and other materials including, but not limited to, solid wastes.

(2) This chapter does not apply to the following sewage sludge and biosolids management facilities and practices:

(a) The firing of biosolids or sewage sludge in an incinerator.

(b) The placing or disposal of sewage sludge in facilities other than municipal solid waste landfills (e.g., the placement of sewage sludge at a surface disposal site).

(3) Except as provided in (g) of this subsection, the following solid wastes are not regulated under this chapter:

(a) Sludge generated at an industrial facility during the treatment of industrial wastewater, including when such a facility combines their industrial wastewater with their domestic sewage.

(b) Sewage sludge determined to be hazardous in accordance with chapter 70.105 RCW or rules adopted thereunder.

(c) Sewage sludge with a concentration of polychlorinated biphenyls (PCBs) equal to or greater than 50 milligrams per kilogram of total solids (dry weight basis).

(d) Ash generated during the firing of sewage sludge or biosolids in an incinerator.

(e) Grit or screenings generated during preliminary treatment of domestic sewage in a treatment works.

(f) Sludge generated during the treatment of either surface water or groundwater used for drinking water.

(g) Commercial or industrial septage or a mixture of domestic septage and commercial or industrial septage except as allowed in accordance with this subsection.

(i) Grease trap wastes from restaurants and similar food service facilities may be mixed with domestic septage up to twenty-five percent by volume.

(ii) On a case-by-case basis, on request of a septage management facility or at the department's discretion, the department may designate other commercial or industrial septage as septage that is "domestic in quality" and require the septage to be managed in accordance with the provisions of this chapter.

(iii) At no time may the combined total of grease trap wastes and other commercial or industrial septage mixed with domestic septage exceed twenty-five percent by volume.