Wash. Rev. Code § 81.04.110
Complaint may be made by the commission of its own motion or by any person or corporation, chamber of commerce, board of trade, or any commercial, mercantile, agricultural or manufacturing society, or any body politic or municipal corporation, by petition or complaint in writing, setting forth any act or thing done or omitted to be done by any public service company or any person, persons, or entity acting as a public service company in violation, or claimed to be in violation, of any provision of law or of any order or rule of the commission.
When two or more public service companies or a person, persons, or entity acting as a public service company, (meaning to exclude municipal and other public corporations) are engaged in competition in any locality or localities in the state, either may make complaint against the other or others that the rates, charges, rules, regulations or practices of such other or others with or in respect to which the complainant is in competition, are unreasonable, unremunerative, discriminatory, illegal, unfair or intending or tending to oppress the complainant, to stifle competition, or to create or encourage the creation of monopoly, and upon such complaint or upon complaint of the commission upon its own motion, the commission shall have power, after notice and hearing as in other cases, to, by its order, subject to appeal as in other cases, correct the abuse complained of by establishing such uniform rates, charges, rules, regulations or practices in lieu of those complained of, to be observed by all of such competing public service companies in the locality or localities specified as shall be found reasonable, remunerative, nondiscriminatory, legal, and fair or tending to prevent oppression or monopoly or to encourage competition, and upon any such hearing it shall be proper for the commission to take into consideration the rates, charges, rules, regulations and practices of the public service company or companies complained of in any other locality or localities in the state.
All matters upon which complaint may be founded may be joined in one hearing, and no motion shall be entertained against a complaint for misjoinder of complaints or grievances or misjoinder of parties; and in any review of the courts of orders of the commission the same rule shall apply and pertain with regard to the joinder of complaints and parties as herein provided: PROVIDED, All grievances to be inquired into shall be plainly set forth in the complaint. No complaint shall be dismissed because of the absence of direct damage to the complainant.
Upon the filing of a complaint, the commission shall cause a copy thereof to be served upon the person or company complained of, which shall be accompanied by a notice fixing the time when and place where a hearing will be had upon such complaint. The time fixed for such hearing shall not be less than ten days after the date of the service of such notice and complaint, excepting as herein provided. Rules of practice and procedure not otherwise provided for in this title may be prescribed by the commission.
RCW 81.04.110
Intent-1994 c 37: "It is the intent of the legislature to clarify that the utilities and transportation commission has the authority to make more efficient use of its resources, provide quicker resolution of complaints regarding transportation tariff matters, eliminate duplicative hearings on classification and violation matters, and to make certain that criminal proceedings involving alleged violations of transportation tariffs not be dismissed because of confusion regarding whether a defendant has received a classification by the commission." [ 1994 c 37 s 1.]