definiens: means the date that ( a ) the Governmental Authority with jurisdiction ove r a Remedial Action issues a written notice indicatin g that no further action, other than operation and maintenance of institutional or engineering controls is require d, or ( b ) if, after requesting in writing such a no tice from such a Governmental Authority, despite the Party responsib le for such a Remedial Action having reasonably com pleted the requirements to obtain such a written notice, n o such written notice is issued within 90 days afte r such Governmental Authority ’s receipt of such request or any longer time period granted to such Governmenta l Authority under the relevant Environmental Law, the n the Remediation Completion Date shall mean the da te that an engineering firm mutually selected by the P arties and consistently ranked on the list of the T op 200 Environmental Firms published by the Engineering Ne ws - Record, and employing an Environmental Professio nal as defined in 40 CFR Part 312.10 and ASTM E1527 - 13, concurs that no further action, other than operati on and maintenance of institutional or engineering control s, is required