R.I. Gen. Laws § 46-16-6: Recognition of certificates issued by commission.

(a) Certificates issued by the commission shall be recognized and given in connection with personnel employed in or having responsibilities for plants discharging into any waters of this state.

(b) Nothing in this chapter shall be construed to require any person to have a certificate in order to be employed in the operation of a sewage or other waste treatment plant. Those requirements, if any, shall be as set forth in or pursuant to other laws of this state; provided that in any case where a certificate is required, an appropriate certificate issued by the commission shall be accepted in lieu of any certificate otherwise required.