All applicants for licensure under this chapter, except as provided in RCW 18.210.180, must pass a written examination administered by the board and must also meet the following minimum requirements:

(1) A high school diploma or equivalent; and

(2) A minimum of four years of experience, as approved by the board, showing increased responsibility for the design of on-site wastewater treatment systems. The experience should include site soil assessment, hydraulics, topographic delineations, use of specialized treatment processes and devices, microbiology, and construction practices. Completion of satisfactory college-level coursework or successful participation in a board-approved internship or mentoring program may be substituted for up to two years of the experience requirement.