(a) To carry out the purposes of this Act or any rule, regulation, order, or permit, issued thereunder, the department or its authorized representative, upon presentation of his credentials:

(1) shall have a right of entry to, upon, or through any premises in which any effluent source is located or in which any records are required to be maintained;

(2) may at reasonable times have access to and copy any records required to be maintained;

(3) may inspect any monitoring equipment or method which is required; and

(4) may have access to and sample any discharges or pollutants to waters or to publicly owned treatment works resulting directly or indirectly from activities or operations of the owner or operator of the premises in which the effluent source is located.

(b) For the purposes of this section the term "effluent source" shall mean:

(1) a point source of the discharge of pollutants or

(2) a source of introduction of pollutants into publicly owned treatment works by an industrial user.