(b) Proceedings on an application by an owner of an existing major electric generating facility to modify such existing facility or site a new major electric generating facility adjacent or contiguous to such existing facility, shall be completed in all respects in a manner consistent with federally delegated or approved environmental permitting authority, including a final decision by the board, within six months from the date of a determination by the chair that such application complies with section one hundred sixty-four of this article, whenever such application demonstrates that the operation of the modified facility, or of the existing facility and new facility in combination, would result in:

(i) a decrease in the rate of emission of each of the relevant siting air contaminants. For facilities that are partially replaced or modified, the percentage decrease shall be calculated by comparing the potential to emit of each such contaminant of the existing unit that is to be modified or replaced as of the date of application under this article to the future potential to emit each such contaminant of the modified or replacement unit as proposed in the application. For facilities that are sited physically adjacent or contiguous to an existing facility, the percentage decrease shall be calculated by comparing the potential to emit of each such contaminant of the existing facility as of the date of application under this article, to the future potential to emit each such contaminant of the existing and new facility combined as proposed in the application;

(ii) a reduction of the total annual emissions of each of the relevant siting air contaminants emitted by the existing facility. The percentage reduction shall be calculated by comparing (on a pounds-per-year basis) the past actual emissions of each of the relevant siting air contaminants emitted by the existing facility averaged over the three years preceding the date of application under this article, to the annualized potential to emit each such contaminant of the modified facility or of the combined existing and new facility as proposed in the application;

(iii) introduction of a new cooling water intake structure where such structure withdraws water at a rate equal to or less than closed-cycle cooling; and

(iv) a lower heat rate than the heat rate of the existing facility. The applicant shall supply the details of the analysis in the application and such supporting information, as may be requested by the board or, in the exercise of federally delegated or approved environmental permitting authority, the department of environmental conservation, necessary to show compliance with the requirements of subparagraphs (i) through (iv) of this paragraph. The board may extend the deadline in extraordinary circumstances by no more than three months in order to give consideration to specific issues necessary to develop an adequate record. The board shall render a final decision on the application by the aforementioned deadlines unless such deadlines are waived by the applicant. If, at any time subsequent to the commencement of the hearing, there is a material and substantial amendment to the application, the deadlines may be extended by no more than three months, unless such deadline is waived by the applicant, to consider such amendment. 5. If an application for an amendment of a certificate proposing a change in the facility is likely to result in any material increase in any environmental impact of the facility or a substantial change in the location of all or a portion of such facility, a hearing shall be held in the same manner as a hearing on an application for a certificate. The board shall promulgate rules, regulations and standards under which it shall determine whether hearings are required under this subdivision and shall make such determinations.