Realizing that conditions may exist in operations under which certain state standards will not have practical application, the director of the department of labor and industries or authorized representative may, pursuant to this section, sections 8 or 9 of the Washington Industrial Safety and Health Act (chapter 80, Laws of 1973, RCW 49.17.080 and 49.17.090) and appropriate administrative rules of this state and the department of labor and industries and upon receipt of application and after adequate investigation by the department, permit a variation from these requirements when other means of providing an equivalent measure of protection are afforded. Such variation granted must be limited to the particular case or cases covered in the application for variance and may be revoked for cause. The order granting a variance must be conspicuously posted on the premises and must remain posted during the time it is in effect. A copy of the variance must be available at the work site. All requests for variances from safety and health standards included in this chapter, must be made in writing to the director of the department of labor and industries at Olympia, Washington, or duly authorized representative, Department of Labor and Industries, P.O. Box 44600, Olympia, Washington 98504-4600.