Whenever the Administrator publishes a proposed effluent standard, the notice thereof published in the Federal Register shall include a statement of the basis and purpose of the standard or a summary thereof. This statement shall include:

(a) The purpose of the proposed standard;

(b) An explanation of how the proposed standard was derived;

(c) Scientific and technical data and studies supporting the proposed standard or references thereto if the materials are published or otherwise readily available; and

(d) Such other information as may be reasonably required to set forth fully the basis of the standard.

Where the notice of the proposed rulemaking summarizes the full statement of basis and purpose, or incorporates documents by reference, the documents thus summarized or incorporated by reference shall thereupon be made available by the Agency for inspection and copying by any interested person.