Model Clearinghouse Information Storage and Retrieval System
Record Details

Issue:

Mayflower Wind, LLC (Mayflower Wind) has proposed the construction of an 
offshore wind renewable energy generation project on the Outer 
Continental Shelf (OCS) off the southern coast of Massachusetts (Lease 
Area OCS-A 0521). The Mayflower Wind project triggers the requirements 
for Prevention of Significant Deterioration (PSD) review as a major 
source with anticipated significant emissions of sulfur doxide (SO2), 
carbon monoxide (CO), oxides of nitrogen (NOX), volatile organic 
compounds (VOCs), particulate matter (PM) with diameter 10 microns or 
less (PM10), PM with diameter 2.5 microns or less (PM2.5), and 
Greenhouse Gases (GHG). As a result, air quality modeling will be 
conducted for SO2, CO, NO2, O3, PM10, and PM2.5 to demonstrate 
compliance with the National Ambient Air Quality Standards (NAAQS) and 
appropriate PSD Increments. Additionally, the Mayflower Wind project 
will trigger Nonattainment New Source Review (NNSR) for the O3 
precursors NOX and VOCs.

Mayflower Wind has requested to use an alternative model, as provided in 
Section 3.2 of the Guideline on Air Quality Models (40 CFR Part 51, 
Appendix W), to conduct its PSD air quality modeling analysis. 
Specifically, Mayflower has requested to use the Coupled Ocean-Atmosphere 
Response Experiment (COARE) bulk flux algorithm, as implemented in the 
AERCOARE meteorological data preprocessor program, to prepare 
meteorological data for use in the American Meteorological 
Society/Environmental Protection Agency Regulatory Model (AERMOD) 
dispersion program over the preferred Offshore and Coastal Dispersion 
(OCD) model to assess ambient impacts in a marine environment.

EPA Region 1 has conducted a thorough review of the Mayflower Wind 
request and has found the proposed application of the alternative model 
is satisfactory and addresses the requirements of the Guideline, Section 
3.2.2(b), Condition (3) and the subsequent five elements contained in 
Section 3.2.2(e). As such, pursuant to Sections 3.0(b) and 3.2.2(a), EPA 
Region 1 currently intends to approve the use of AERCOARE-AERMOD as an 
acceptable alternative model for the Mayflower Wind project.

C/H Response:

The Model Clearinghouse concurs with EPA Region 1’s proposed approval of 
a coupled AERCOARE-AERMOD alternative modeling approach for the air 
quality modeling analysis required in the Mayflower Wind project based 
the alternative model justification package provided by Mayflower Wind, 
LLC and the review documentation in the alternative model concurrence 
request memorandum provided by EPA Region 1. The Model Clearinghouse 
encourages EPA Region 1 to respond to Mayflower Wind, LLC and to the 
docket for federal permitting actions related to the Mayflower Wind 
project with a letter of alternative model approval, as appropriate. The 
information associated with the EPA Region 1 alternative model approval 
and the Model Clearinghouse concurrence should be available for comment 
during the appropriate public comment period(s).

Given the possible importance of platform downwash and shoreline 
fumigation, the Model Clearinghouse continues to recommend caution and 
careful review before additional alternative model considerations of the 
coupled AERCOARE-AERMOD model methodology in other projects. This case-
specific Model Clearinghouse concurrence does not constitute a generic 
approval of a coupled AERCOARE-AERMOD approach for other applications 
elsewhere. However, the scope of the technical assessment submitted here 
and with similar AERCOARE-AERMOD alternative model requests continue to 
provide a good basis for such considerations.

Memo:  Model Clearinghouse review of an alternative model application of 
Alternative Model AERCOARE in Conjunction with AERMOD in Support of 
Outer Continental Shelf PSD air permitting of the Mayflower Wind Project
        Dated: December 13, 2022
        From:  George Bridgers, Model Clearinghouse Director
                 Air Quality Modeling Group, Air Quality Assessment Division, 
                 Office of Air Quality Planning and Standards
        To:    Patrick Bird, Manager
                 Air Permits, Toxics, and Indoor Programs Branch, Air and Radiation Division
                 EPA Region 1, Boston, Massachusetts
               Lynne Hamjian, Director
                 Air and Radiation Division
                 EPA Region 1, Boston, Massachusetts
                 
Memo:  Concurrence Request for Approval of Alternative Model AERCOARE in 
Conjunction with AERMOD, in Support of Outer Continental Shelf PSD air 
permitting of the Mayflower Wind Project
        Dated: November 18, 2022
        From:  Patrick Bird, Manager
                 Air Permits, Toxics, and Indoor Programs Branch, Air and Radiation Division
                 EPA Region 1, Boston, Massachusetts
        Thru:  Lynne Hamjian, Director
                 Air and Radiation Division
                 EPA Region 1, Boston, Massachusetts
        To:    George Bridgers, Director of Model Clearinghouse
                 Air Quality Modeling Group, Office of Air Quality Planning and Standards

Memo:  Mayflower Wind Energy – Request for use of COARE Bulk Flux Algorithm to 
Generate Hourly Meteorological Data for use with AERMOD
            Dated: October 17, 2022