Notwithstanding any provision of the law to the contrary, except RCW 70A.15.5120 through 70A.15.5150, the department of ecology, upon its approval of any plan (or part thereof) required or permitted under the federal clean air act, shall have the authority to enforce all regulatory provisions within such plan (or part thereof): PROVIDED, That departmental enforcement of any such provision which is within the power of an activated authority to enforce shall be initiated only, when with respect to any source, the authority is not enforcing the provisions and then only after written notice is given the authority.