Md. Code, Environment § 9–331

By rule, regulation, order, permit, or otherwise, the Department may require the owner or operator of any source of a discharge of pollutants or of any source that is an industrial user of a publicly owned treatment works:

(1) To keep records;

(2) To make reports;

(3) To install, calibrate, use, and maintain monitoring equipment or methods, including, where appropriate, biological monitoring methods;

(4) To sample discharges in accordance with the methods, at the locations, at the intervals, and in the manner the Department requires; and

(5) To provide to the Department any information that the Department reasonably requires about:

(i) Discharge of pollutants into the waters of this State; or

(ii) Introduction of pollutants into publicly owned treatment works.