Wash. Rev. Code § 49.12.091
After an investigation has been conducted by the department of wages, hours and conditions of labor subject to chapter 16, Laws of 1973 2nd ex. sess., the director shall be furnished with all information relative to such investigation of wages, hours and working conditions, including current statistics on wage rates in all occupations subject to the provisions of chapter 16, Laws of 1973 2nd ex. sess. Within a reasonable time thereafter, if the director finds that in any occupation, trade or industry, subject to chapter 16, Laws of 1973 2nd ex. sess., the wages paid to employees are inadequate to supply the necessary cost of living, but not to exceed the state minimum wage as prescribed in RCW 49.46.020, as now or hereafter amended, or that the conditions of labor are detrimental to the health of employees, the director shall have authority to prescribe rules and regulations for the purpose of adopting minimum wages for occupations not otherwise governed by minimum wage requirements fixed by state or federal statute, or a rule or regulation adopted under such statute, and, at the same time have the authority to prescribe rules and regulations fixing standards, conditions and hours of labor for the protection of the safety, health and welfare of employees for all or specified occupations subject to chapter 16, Laws of 1973 2nd ex. sess. Thereafter, the director shall conduct a public hearing in accordance with the procedures of the administrative procedure act, chapter 34.05 RCW, for the purpose of the adoption of rules and regulations fixing minimum wages and standards, conditions and hours of labor subject to the provisions of chapter 16, Laws of 1973 2nd ex. sess. After such rules become effective, copies thereof shall be supplied to employers who may be affected by such rules and such employers shall post such rules, where possible, in such place or places, reasonably accessible to all employees of such employer. After the effective date of such rules, it shall be unlawful for any employer in any occupation subject to chapter 16, Laws of 1973 2nd ex. sess. to employ any person for less than the rate of wages specified in such rules or under conditions and hours of labor prohibited for any occupation specified in such rules: PROVIDED, That this section shall not apply to sheltered workshops.
RCW 49.12.091