(1) A certificate shall specify, among other things, the name of the worker with a disability, the name of the employer, the occupation in which the worker with a disability is to be employed, the authorized subminimum wage rate and the period of time during which such wage rate may be paid.

(2) A certificate shall be effective for a period to be designated by the director or an authorized representative and a worker with a disability employed under such certificate may be paid subminimum wages only during the effective period of the certificate.

(3) The wage rate set in the certificate shall be fixed at a figure designed to reflect adequately the worker with a disability's earning capacity. No wage rate shall be fixed at less than seventy-five percent of the applicable minimum wage under RCW 49.46.020 unless, after investigation a lower rate appears to be clearly justified.

(4) Any money received by a worker with a disability by reason of any state or federal pension or compensation program for workers with a disability shall not be considered as offsetting any part of the wage or remuneration due the worker by the employer.

(5) The worker with a disability or trainee shall be paid not less than one and one-half times the regular rate for hours worked in excess of forty in the workweek or eight in the workday.

(6) The terms of any certificate, including the subminimum wage rate specified therein, may be amended by the director or an authorized representative upon written notice to the parties concerned, if the facts justify such amendment.