1020-00004 · Greenfield Agricultural Partners · Air Permit

response-idnr-air-completeness-comments.docx DOCUMENT M&A / Corporate

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CALDERWOOD & HARKNESS LLP Attorneys at Law

801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309

Telephone: (515) 284-7600 Facsimile: (515) 284-7601

May 15, 2023

Via Electronic Mail and U.S. Mail

Jonathan Kreske, P.E. Environmental Engineer Air Quality Bureau Iowa Department of Natural Resources 502 East 9th Street Des Moines, Iowa 50319

Re: Response to Completeness Review Comments — Prevention of Significant Deterioration (PSD) Construction Permit Application

Applicant: Greenfield Agricultural Partners LLC Project: Muscatine Expansion Facility Site Address: 14800 Highway 61 North, Muscatine, Iowa 52761 Muscatine County Parcel ID: 0735-19-200-004 Application Filed: April 28, 2023 C&H Matter No.: 1020-00004

Dear Mr. Kreske:

I. Introduction

Calderwood & Harkness LLP represents Greenfield Agricultural Partners LLC ("GAP") in connection with the above-referenced Prevention of Significant Deterioration ("PSD") Construction Permit application filed with the Iowa Department of Natural Resources ("IDNR") Air Quality Bureau ("AQB") on April 28, 2023, pursuant to Iowa Administrative Code 567—Chapter 33. The application seeks authorization for the construction of the Muscatine Expansion Facility ("MEF"), a greenfield soybean processing and specialty fertilizer blending facility to be located on a 147-acre site in Muscatine County, Iowa, at 14800 Highway 61 North, Muscatine, Iowa 52761 (Muscatine County Parcel ID 0735-19-200-004). As described in detail in the application, the MEF will comprise a soybean crush operation with a design capacity of 3,200 tons per day and a granular fertilizer blending line with a capacity of 450 tons per day.

We acknowledge receipt of AQB's completeness review comments, which were transmitted via electronic mail on or about May 10, 2023. In those comments, AQB identified three areas in which supplemental information is required before a completeness determination can be issued for the PSD application. Specifically, AQB requested additional detail concerning: (1) the AERMOD receptor grid spacing and configuration used in the air dispersion modeling analysis; (2) startup and shutdown emission estimates for emission units EU-01 and EU-02; and (3) supporting documentation for the proposed baghouse filter particulate matter outlet concentration specification for EU-04.

This letter provides GAP's responses to each of the three items identified by AQB, together with supplemental documentation and revised application materials as described herein. These responses have been prepared in coordination with Pinnacle Environmental Consultants Inc. ("Pinnacle"), GAP's environmental consultant, under the direction of Dr. Leonard Fisk, P.E., Principal of Pinnacle's Air Quality Practice, located at 1120 Ingersoll Avenue, Suite 210, Des Moines, Iowa 50309. Dr. Fisk has supervised the preparation of all technical analyses and supplemental materials enclosed with this response.

It is GAP's understanding, based on communications with your office, that upon satisfactory receipt of these supplemental materials, AQB anticipates issuing a completeness determination for the PSD application by May 19, 2023. GAP appreciates AQB's diligent review and is committed to providing all information necessary to facilitate a timely completeness determination and progression of the permitting process.

The responses to each of AQB's three comments are set forth below in the order in which they were raised in AQB's May 10, 2023 correspondence.

II. Response to Comment No. 1: AERMOD Receptor Grid Spacing and Configuration

A. Summary of IDNR Comment

In its completeness review comments, AQB requested additional detail regarding the receptor grid configuration used in the AERMOD air dispersion modeling analysis submitted as Appendix C to the PSD application. Specifically, AQB asked GAP to confirm and document: (i) the receptor grid spacing intervals from the facility fenceline outward to the maximum extent of the modeling domain; (ii) the maximum extent of the receptor grid in each cardinal direction; and (iii) the placement of discrete receptors at the nearest residential receptor location, including the distance and direction of that receptor relative to the proposed emission sources. AQB noted that while Appendix C contained modeling output files and graphical concentration plots, the receptor grid configuration narrative did not fully describe the grid spacing intervals and nesting approach used.

B. GAP Response

GAP and Pinnacle appreciate AQB's careful review of the AERMOD modeling documentation and are pleased to provide the following clarification and supplemental information in response to this comment.

The AERMOD air dispersion modeling analysis submitted with the PSD application was performed using AERMOD Version 23.1, which is the current regulatory version of the model approved by the U.S. Environmental Protection Agency ("EPA") for PSD and other New Source Review applications. The modeling was conducted in accordance with both IDNR's Air Dispersion Modeling Guidelines, as published by AQB, and EPA's Guideline on Air Quality Models, codified at Appendix W to 40 C.F.R. Part 51. GAP confirms the following receptor grid configuration details:

Cartesian Receptor Grid. The primary receptor grid is a Cartesian receptor grid with 50-meter spacing extending from the facility fenceline outward to a distance of 5 kilometers in all four cardinal directions. This grid encompasses a total modeling domain of approximately 10 kilometers by 10 kilometers centered on the facility, providing comprehensive spatial coverage for the purpose of identifying the location of maximum modeled concentrations for all criteria pollutants subject to the PSD review.

Nested Fine Grid. A nested finer-resolution Cartesian grid with 25-meter spacing was employed within the first 500 meters of the facility fenceline in all directions. This nested grid was implemented to provide enhanced spatial resolution in the near-field area surrounding the facility, where maximum ground-level concentrations are most likely to occur. GAP acknowledges that this detail was inadvertently omitted from the modeling protocol narrative included in Section C.2 of Appendix C to the application. The nested grid was, however, correctly implemented in the AERMOD input files that were submitted with the application, and the modeling results reflect the use of this finer-resolution grid. GAP regrets the oversight in the narrative description and has prepared a supplemental explanation that is included with the enclosed materials.

Discrete Receptors. Discrete (flagpole) receptors were placed at the nearest residential receptor location, which is situated approximately 0.42 miles (2,218 feet) east-northeast of the proposed primary stack location for emission unit EU-01. The discrete receptors were placed at a height of 1.5 meters above ground level, consistent with EPA guidance for representing breathing-zone height at residential locations. The coordinates and elevation of the nearest residential receptor were verified by Pinnacle using publicly available Muscatine County GIS parcel data and a field reconnaissance survey conducted on March 8, 2023.

Terrain Data. Terrain elevations were incorporated into the modeling analysis using U.S. Geological Survey ("USGS") National Elevation Dataset ("NED") data at 1/3 arc-second resolution (approximately 10-meter horizontal resolution). The terrain data were processed through the AERMAP terrain pre-processor (Version 18081) to generate receptor and source elevations and hill-height scale values for input into AERMOD. The terrain in the vicinity of the MEF site is generally flat to gently rolling, with elevation variations of approximately 30 feet across the modeling domain, which is characteristic of the Mississippi River valley terrain in Muscatine County.

Meteorological Data. The modeling analysis employed a 5-year meteorological dataset from the Muscatine Municipal Airport (station identifier KMUT), covering the period January 1, 2018, through December 31, 2022. Surface meteorological data from KMUT were paired with upper-air data from the Davenport, Iowa, National Weather Service station (station identifier KDVN), which is the nearest upper-air sounding station. The meteorological data were processed using the AERMET meteorological pre-processor (Version 22112) in accordance with both EPA and IDNR guidance, including the application of the Bulk Richardson Number approach for determining the planetary boundary layer height and the use of AERSURFACE (Version 21112) to characterize surface roughness, albedo, and Bowen ratio values for the land use surrounding the KMUT station.

Supplemental Receptor Grid Map. Enclosed herewith as Attachment A is a supplemental receptor grid map prepared by Pinnacle that depicts all Cartesian grid receptors (both the 50-meter primary grid and the 25-meter nested grid), discrete receptors at the nearest residential receptor location, and the facility property boundary. The map includes grid spacing annotations, a distance scale, and a north arrow. The map was prepared using GIS software and overlaid on current aerial photography of the project area for reference.

Dr. Fisk of Pinnacle has verified the receptor grid configuration and confirms that it is fully consistent with IDNR's Air Dispersion Modeling Guidelines and EPA's Guideline on Air Quality Models (Appendix W to 40 C.F.R. Part 51). The receptor grid provides adequate spatial resolution and geographic extent to identify maximum modeled concentrations at all ambient air locations, including the nearest residential receptor and the facility fenceline.

GAP also takes this opportunity to confirm that the maximum modeled impact results presented in the application remain unchanged as a result of this supplemental clarification. Specifically, the 24-hour PM₁₀ impact, which represents the highest modeled concentration relative to the applicable National Ambient Air Quality Standard ("NAAQS"), was determined to be 38.2 µg/m³ (modeled concentration) plus 72 µg/m³ (background concentration), for a total of 110.2 µg/m³. This total is well below the 24-hour PM₁₀ NAAQS of 150 µg/m³, providing a compliance margin of approximately 39.8 µg/m³. Similarly, all other criteria pollutant concentrations were demonstrated to be in compliance with the applicable NAAQS and PSD increments for all averaging periods.

Finally, GAP notes that Muscatine County is designated as attainment or unclassifiable for all criteria pollutants under the Clean Air Act, thereby confirming the applicability of the PSD permitting program and the PSD increment analysis. The increment consumption analysis presented in Appendix C of the application demonstrates that the MEF's emissions will not cause or contribute to a violation of any applicable PSD increment.

III. Response to Comment No. 2: Startup and Shutdown Emission Estimates for EU-01 and EU-02

A. Summary of IDNR Comment

AQB's second completeness review comment requested clarification of the emission estimates for EU-01, the natural gas-fired process heater rated at 120 MMBtu/hr heat input capacity, and EU-02, the soybean dryer rated at 80 MMBtu/hr heat input capacity and also fired on natural gas. Specifically, AQB noted that the application narrative and the emissions inventory presented in Table 4-2 of the application included only steady-state potential-to-emit ("PTE") figures calculated at maximum rated capacity and continuous operation (8,760 hours per year). AQB observed that the application did not separately quantify or discuss emissions during transient startup and shutdown operating periods for these two emission units. AQB asked GAP to clarify whether startup and shutdown emissions were included within the PTE calculations already presented, or whether startup and shutdown emissions represent additional emissions not accounted for in the application's emission inventory and PTE determinations.

B. GAP Response

GAP appreciates AQB's request for clarification on this point. The treatment of startup and shutdown emissions is an important aspect of the PTE determination, and GAP is pleased to provide the following detailed response, which has been prepared by Pinnacle in coordination with GAP's operations and engineering teams.

Basis for Steady-State PTE Calculations. The PTE calculations for EU-01 and EU-02 presented in Table 4-2 of the original application were based on maximum continuous steady-state operation at rated capacity — specifically, 120 MMBtu/hr for EU-01 and 80 MMBtu/hr for EU-02 — for 8,760 hours per year (i.e., continuous year-round operation). This methodology inherently represents a conservative, upper-bound estimate of annual emissions because it assumes both units operate at their maximum rated heat input capacity without interruption for the entire calendar year. In practice, of course, actual operations will include periods of reduced load, maintenance outages, and seasonal variations in production schedules, all of which would result in actual emissions below the calculated PTE values.

Startup and Shutdown Emissions Are Not Separately Additive. GAP clarifies that startup and shutdown emissions for EU-01 and EU-02 are not separately additive to the steady-state PTE figures reported in the application. This conclusion is based on the following technical considerations:

(a) Rapid Achievement of Stable Combustion. Both EU-01 and EU-02 are natural gas-fired combustion units that achieve stable combustion conditions rapidly upon ignition. Based on manufacturer specifications and operating experience with comparable equipment, the estimated startup duration is approximately 30 minutes per event for EU-01 and approximately 20 minutes per event for EU-02. During these brief startup periods, the units are operating at reduced firing rates, and emissions are therefore lower on a mass-per-hour basis than during steady-state maximum-rate operation.

(b) Reduced Firing Rates During Startup. During startup, burner firing rates for both EU-01 and EU-02 are maintained at reduced capacity, typically in the range of approximately 25% to 40% of rated heat input. Because the mass emission rates for criteria pollutants are directly proportional to the rate of fuel combustion, the reduced firing rates during startup result in lower mass emission rates (expressed in pounds per hour) than the maximum steady-state rates used in the PTE calculations.

(c) BACT Controls Operational During Startup. The low-NOₓ burners with flue gas recirculation ("FGR"), which constitute the proposed Best Available Control Technology ("BACT") for NOₓ control on EU-01 and EU-02, are operational during startup. GAP acknowledges that during the initial burner stabilization phase — estimated to last approximately the first 10 minutes of each startup event — NOₓ emission rates may be slightly elevated on a pounds-per-MMBtu basis relative to the steady-state BACT emission limit. Pinnacle estimates that the NOₓ emission rate during this initial stabilization phase is approximately 0.050 lb/MMBtu, which declines to the BACT limit of 0.036 lb/MMBtu upon full burner stabilization. This brief period of marginally elevated emission rates, combined with the reduced firing rate, results in only a negligible incremental contribution to annual emissions above the steady-state PTE.

(d) Negligible Shutdown Emissions. Shutdown emissions for both EU-01 and EU-02 are negligible. Both units undergo controlled ramp-down of the burner firing rate during shutdown, during which emissions decline in proportion to the decreasing fuel combustion rate. There is no period of elevated emissions during shutdown, and the controlled ramp-down process does not produce transient emission spikes.

Supplemental Startup/Shutdown Emission Calculations. Notwithstanding the foregoing, and to provide AQB with complete documentation, Pinnacle has prepared supplemental startup and shutdown emission calculations for EU-01 and EU-02. These calculations conservatively estimate the incremental emissions attributable to startup and shutdown events above the steady-state PTE basis, as follows:

EU-01 (Natural Gas-Fired Process Heater, 120 MMBtu/hr): GAP estimates approximately 12 startup events per year and 12 shutdown events per year for EU-01, based on the anticipated operating schedule, which includes planned maintenance outages and seasonal operational adjustments. Based on the startup emission profile described above (30-minute duration, 25–40% firing rate, 0.050 lb/MMBtu NOₓ during the first 10 minutes declining to 0.036 lb/MMBtu), Pinnacle calculates incremental startup NOₓ emissions of approximately 0.08 tons per year ("tpy") above the steady-state PTE. Incremental shutdown emissions are negligible and are estimated at less than 0.01 tpy NOₓ.

EU-02 (Soybean Dryer, 80 MMBtu/hr): GAP estimates approximately 24 startup events per year and 24 shutdown events per year for EU-02. The higher frequency of startup and shutdown events for EU-02 reflects the seasonal cycling of the soybean dryer in connection with soybean processing campaigns, which are driven by harvest schedules and market conditions. Based on the startup emission profile described above (20-minute duration, 25–40% firing rate, similar elevated lb/MMBtu rate during initial stabilization), Pinnacle calculates incremental startup NOₓ emissions of approximately 0.05 tpy above the steady-state PTE. Incremental shutdown emissions are negligible and are estimated at less than 0.01 tpy NOₓ.

Total Incremental Startup/Shutdown Emissions: The total incremental startup and shutdown NOₓ emissions for both EU-01 and EU-02 combined are approximately 0.13 tpy. This figure is well within the aggregate facility-wide PTE of 312 tpy NOₓ already reported in the application and represents approximately 0.04% of the total facility NOₓ PTE. The incremental startup/shutdown emissions are therefore de minimis and do not materially affect the facility's PTE, BACT determinations, NAAQS compliance demonstrations, or PSD increment consumption analyses.

Other Criteria Pollutants. Pinnacle has conducted a similar analysis for PM₁₀, PM₂.₅, carbon monoxide ("CO"), volatile organic compounds ("VOC"), sulfur dioxide ("SO₂"), and greenhouse gases ("GHG," expressed as CO₂-equivalent) during startup and shutdown of EU-01 and EU-02. This analysis confirms that transient startup and shutdown emissions for all of these pollutants are de minimis relative to the steady-state PTE and do not change the application's overall emission inventory, BACT determinations, NAAQS compliance demonstrations, or PSD increment consumption analyses. The detailed calculations are included in the revised Table 4-2 enclosed herewith.

Revised Table 4-2. Enclosed herewith as Attachment B is a revised Table 4-2 (Emission Summary) for the MEF. The revised table now includes a footnote and supplemental line items that separately quantify startup and shutdown emissions for EU-01 and EU-02 alongside the steady-state PTE figures. This revision is intended to provide AQB with a comprehensive and transparent accounting of all emissions, including transient operating modes, consistent with AQB's request for clarification.

GAP confirms that the aggregate facility-wide PTE figures reported in the original application remain valid and are unchanged by this supplemental analysis. The facility-wide PTE values are summarized as follows:

These PTE values continue to reflect the maximum potential emissions of the facility, inclusive of all emission units and operating modes, and serve as the basis for the BACT analysis, NAAQS compliance demonstration, and PSD increment consumption analysis presented in the application.

IV. Response to Comment No. 3: Baghouse Filter PM Outlet Specification for EU-04

A. Summary of IDNR Comment

AQB's third completeness review comment requested supplemental documentation supporting the proposed particulate matter ("PM") outlet concentration specification of 0.005 grains per dry standard cubic foot ("gr/dscf") for the baghouse filters controlling emissions from EU-04. Emission unit EU-04 encompasses material handling and storage operations at the MEF, including grain elevators, enclosed belt conveyors, storage bin venting, and fertilizer product loadout operations. AQB noted that the BACT analysis included in the application asserted a 99.5% control efficiency for the proposed baghouse system but did not provide vendor performance data, equipment design specifications, or references to comparable installations supporting the proposed outlet concentration of 0.005 gr/dscf. AQB requested that GAP submit such supplemental documentation to support the technical feasibility and achievability of the proposed emission limit.

B. GAP Response

GAP appreciates AQB's request for additional supporting documentation and is pleased to provide the following detailed response, together with the supplemental materials enclosed as Attachment C.

Description of EU-04. Emission unit EU-04 encompasses all particulate-generating material handling and storage operations at the MEF. Specifically, EU-04 includes the following sources:

• Grain receiving operations (truck dump and rail unloading pits)

• Bucket elevator legs (four units serving grain receiving, storage, and processing transfer points)

• Enclosed belt conveyors (six units connecting grain receiving, storage, processing, and loadout areas)

• Grain storage bin venting (eight storage bins with a combined capacity of approximately 2.4 million bushels)

• Fertilizer product storage bin venting (four bins with a combined capacity of approximately 12,000 tons)

• Fertilizer product loadout operations (truck and rail loadout via enclosed spouts with dust collection)

All of the foregoing sources are ducted to centralized pulse-jet fabric filter (baghouse) dust collection systems. The baghouse systems are designed and specified to serve as the primary PM control technology for all material handling and storage emission points within EU-04.

Proposed BACT Control and Specifications. GAP confirms that the proposed BACT control for EU-04 is pulse-jet fabric filter (baghouse) dust collection, with the following design and performance specifications:

• PM Outlet Concentration: 0.005 gr/dscf (approximately 11.4 mg/m³)

• Control Efficiency: 99.5%

• Air-to-Cloth Ratio: 4:1 (gross)

• Filter Media: Polyester felt with polytetrafluoroethylene ("PTFE") membrane laminate

• Cleaning Mechanism: Pulse-jet (compressed air) cleaning with on-demand differential pressure control

• Filter Bag Dimensions: Nominal 6-inch diameter by 120-inch length

The PTFE membrane laminate filter media provides superior particulate filtration performance compared to conventional woven or felted filter media, achieving high collection efficiency across a broad particle size distribution, including fine particulate matter (PM₂.₅). The membrane laminate creates a surface filtration mechanism that captures particulate on the outer surface of the membrane rather than allowing depth penetration into the filter media, resulting in consistently low outlet concentrations and high cleaning efficiency throughout the service life of the filter bags.

Supporting Documentation (Attachment C). In response to AQB's request, GAP has assembled and enclosed herewith as Attachment C the following supplemental documentation supporting the proposed 0.005 gr/dscf outlet concentration specification:

(1) Vendor Performance Guarantee Letter. Attachment C includes a performance guarantee letter from the baghouse equipment manufacturer, confirming that the proposed baghouse system is guaranteed to achieve a PM outlet concentration of 0.005 gr/dscf or less under the specified operating conditions, including the anticipated grain and fertilizer dust loading, air-to-cloth ratio, and volumetric flow rates. The performance guarantee is subject to standard commercial conditions, including proper installation, operation, and maintenance of the baghouse system in accordance with the manufacturer's specifications and recommendations.

(2) Equipment Specification Sheets. Attachment C includes detailed equipment specification sheets for the proposed baghouse units, showing all relevant design parameters, including overall dimensions, number of filter bags per unit, total filtration area, design volumetric flow rate, air-to-cloth ratio, filter media type and weight, cleaning cycle specifications (pulse duration, pulse pressure, cleaning interval), hopper design, and materials of construction. The specification sheets confirm that the equipment is designed and rated to achieve the proposed 0.005 gr/dscf outlet concentration at the air-to-cloth ratio of 4:1 specified in the application.

(3) Comparable Installation Stack Test Data. Attachment C includes a summary of stack test data compiled by Pinnacle Environmental from three comparable soybean processing and grain handling installations in Iowa and Nebraska where the same baghouse technology (pulse-jet fabric filter with PTFE membrane laminate filter media) has been installed and has achieved outlet concentrations at or below 0.005 gr/dscf during compliance stack testing. The three comparable installations, their locations, and the measured outlet concentrations are summarized as follows:

All three comparable installations utilize pulse-jet baghouse systems with PTFE membrane laminate filter media and air-to-cloth ratios in the range of 3.5:1 to 4.5:1, which are comparable to the design parameters proposed for the MEF. The stack test data demonstrate that the proposed 0.005 gr/dscf outlet concentration is readily achievable with this technology and represents a conservative (i.e., slightly higher than demonstrated) performance specification.

(4) RACT/BACT/LAER Clearinghouse References. Attachment C includes references to recent entries in EPA's RACT/BACT/LAER Clearinghouse ("RBLC") database for grain handling and processing facility PSD permits issued within the past five years. These RBLC entries demonstrate that outlet concentrations of 0.005 gr/dscf or lower have been established as BACT for baghouse-controlled grain handling and material storage operations at multiple facilities nationwide. The referenced RBLC entries confirm that the proposed 0.005 gr/dscf outlet specification is consistent with current BACT determinations for this source category and represents achievable, commercially proven technology.

Design Engineer Verification. GAP further confirms that Ridgeline Engineering Group LLC, the facility design engineer for the MEF, has incorporated the baghouse specifications described above into the MEF process and civil engineering design. Thomas Novak, P.E., Project Manager at Ridgeline Engineering Group LLC (7700 Pioneers Boulevard, Suite 105, Lincoln, Nebraska 68506), has verified the adequacy of the air-to-cloth ratio of 4:1 for the anticipated grain and fertilizer dust loading based on the design throughput capacities of the grain receiving, storage, conveying, and fertilizer blending and loadout systems. Mr. Novak has confirmed that the baghouse systems are properly sized and integrated into the facility design to maintain the specified air-to-cloth ratio and outlet concentration across the full range of anticipated operating conditions.

Consistency with Emission Inventory and Modeling. GAP notes that the 0.005 gr/dscf outlet specification, combined with the proposed 99.5% control efficiency, is reflected in the PM₁₀ PTE of 196 tpy and PM₂.₅ PTE of 87 tpy reported for the facility in the original application. These PTE figures formed the basis for the AERMOD air dispersion modeling analysis demonstrating compliance with all applicable NAAQS and PSD increments. No changes to the PM₁₀ or PM₂.₅ PTE figures, the BACT analysis, or the modeling results are required as a result of this supplemental documentation.

V. Enclosures and Attachments Summary

For AQB's convenience, GAP provides the following summary of all supplemental materials enclosed with this response:

Attachment A — Supplemental Receptor Grid Map. AERMOD receptor grid configuration map showing the 50-meter Cartesian receptor grid extending to 5 kilometers from the facility fenceline, the 25-meter nested receptor grid within 500 meters of the fenceline, and discrete receptors placed at the nearest residential receptor location (0.42 miles / 2,218 feet east-northeast of EU-01). The map includes grid spacing annotations, a distance scale, north arrow, facility boundary, and aerial photography basemap.

Attachment B — Revised Table 4-2: Emission Summary with Startup/Shutdown Emission Estimates for EU-01 and EU-02. Revised emission summary table incorporating footnoted line items that separately quantify startup and shutdown emissions for EU-01 and EU-02 alongside steady-state PTE figures. Aggregate facility-wide PTE values remain unchanged: NOₓ 312 tpy, SO₂ 28 tpy, PM₁₀ 196 tpy, PM₂.₅ 87 tpy, CO 245 tpy, VOC 164 tpy, and GHG (CO₂e) 148,600 tpy.

Attachment C — Supplemental Baghouse Documentation. Compilation of supporting documentation for the proposed 0.005 gr/dscf baghouse outlet concentration specification for EU-04, including: (i) vendor performance guarantee letter; (ii) equipment specification sheets; (iii) comparable installation stack test data summary (three Iowa and Nebraska facilities); and (iv) EPA RACT/BACT/LAER Clearinghouse references for recent grain handling and processing facility PSD permits.

Attachment D — Updated Stack-Parameter Spreadsheet. Revised electronic spreadsheet (Microsoft Excel format) containing corrected and updated stack parameters for all emission units EU-01 through EU-06, including stack height, stack inside diameter, exit velocity, exit temperature, and geographic coordinates (UTM Zone 15N, NAD83 datum). The spreadsheet has been updated to incorporate the clarifications and supplemental information provided in response to Comments 1 through 3 above.

VI. Request for Completeness Determination

Based on the foregoing responses and the enclosed supplemental materials, GAP respectfully requests that AQB review the submissions and issue a completeness determination for the PSD Construction Permit application at its earliest convenience. GAP understands, based on prior communications with AQB, that the completeness determination is anticipated by May 19, 2023, and GAP appreciates AQB's diligence in adhering to this timeline.

GAP notes that the project schedule for the MEF contemplates the commencement of the public notice and comment period promptly following issuance of the completeness determination, consistent with the permitting timeline previously discussed with AQB. Timely progression of the permitting process is important to GAP's construction schedule and to the broader project development timeline for the MEF.

GAP remains fully committed to meeting all applicable permitting requirements under the Clean Air Act, Iowa Administrative Code 567—Chapter 33, and all other applicable federal, state, and local regulations. GAP is available and prepared to provide any additional information that AQB may require in connection with the completeness review or the subsequent substantive review of the PSD application.

For the record, GAP has site control of the 147-acre project site identified by Muscatine County Parcel ID 0735-19-200-004, which was acquired from the Reinholt Family Trust on January 20, 2023, as previously documented in Section 2.1 of the application. Additionally, the Muscatine County Board of Supervisors approved Conditional Use Permit No. MC-2022-041 for the MEF on November 15, 2022, authorizing the proposed soybean processing and fertilizer blending use at the project site, as documented in Appendix A to the application.

VII. Availability and Contact Information

GAP and its counsel remain available to discuss these responses or provide any additional information at AQB's request. To facilitate efficient communication, GAP respectfully directs the following categories of inquiries to the appropriate points of contact:

Technical Questions regarding AERMOD air dispersion modeling, emissions calculations, startup/shutdown emission estimates, and baghouse specifications should be directed to:

Dr. Leonard Fisk, P.E. Principal, Air Quality Practice Pinnacle Environmental Consultants Inc. 1120 Ingersoll Avenue, Suite 210 Des Moines, Iowa 50309 Telephone: (515) 331-4200

Email: lfisk@pinnacle-env.com

Legal and Permitting Process Questions should be directed to the undersigned or to:

Rafael Dominguez Lead Associate Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 284-7618

Email: rdominguez@calderwoodharkness.com

GAP In-House Contact for this matter:

Derek Yun Director of Environmental, Health & Safety Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 492-3300

Email: dyun@greenfieldagpartners.com

VIII. Closing

We appreciate AQB's prompt review of the PSD application and the thoroughness of the completeness review comments. GAP looks forward to the completeness determination and to continuing to work cooperatively with AQB throughout the permitting process for the Muscatine Expansion Facility. Please do not hesitate to contact us if you have any questions regarding these responses or the enclosed supplemental materials.

Respectfully submitted,

CALDERWOOD & HARKNESS LLP

By: ________

Cynthia Ho Associate 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 284-7622

Email: cho@calderwoodharkness.com

cc: (via electronic mail)

Patricia Caldwell, General Counsel & VP of Regulatory Affairs, Greenfield Agricultural Partners LLC Derek Yun, Director of Environmental, Health & Safety, Greenfield Agricultural Partners LLC Margaret Solberg, VP of Operations, Greenfield Agricultural Partners LLC James Prentice, Partner, Calderwood & Harkness LLP Rafael Dominguez, Associate, Calderwood & Harkness LLP Dr. Leonard Fisk, P.E., Principal, Pinnacle Environmental Consultants Inc. Thomas Novak, P.E., Project Manager, Ridgeline Engineering Group LLC

Enclosures:

Attachment A — Supplemental Receptor Grid Map Attachment B — Revised Table 4-2 (Emission Summary with Startup/Shutdown Estimates) Attachment C — Supplemental Baghouse Documentation Attachment D — Updated Stack-Parameter Spreadsheet (Excel format)

Pollutant	Facility-Wide PTE (tpy)
NOₓ	312
SO₂	28
PM₁₀	196
PM₂.₅	87
CO	245
VOC	164
GHG (CO₂e)	148,600
Installation	Location	Year Tested	Measured PM Outlet (gr/dscf)
Heartland Grain Processing, LLC	Cedar Rapids, Iowa	2021	0.0038
Platte Valley Ag Cooperative	Columbus, Nebraska	2020	0.0042
Hawkeye Soy Products, Inc.	Iowa Falls, Iowa	2022	0.0031

CALDERWOOD & HARKNESS LLP Attorneys at Law
801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309
Telephone: (515) 284-7600 Facsimile: (515) 284-7601
May 15, 2023
Via Electronic Mail and U.S. Mail
Jonathan Kreske, P.E. Environmental Engineer Air Quality Bureau Iowa Department of Natural Resources 502 East 9th Street Des Moines, Iowa 50319
Re: Response to Completeness Review Comments — Prevention of Significant Deterioration (PSD) Construction Permit Application
Applicant: Greenfield Agricultural Partners LLC Project: Muscatine Expansion Facility Site Address: 14800 Highway 61 North, Muscatine, Iowa 52761 Muscatine County Parcel ID: 0735-19-200-004 Application Filed: April 28, 2023 C&H Matter No.: 1020-00004
Dear Mr. Kreske:
I. Introduction
Calderwood & Harkness LLP represents Greenfield Agricultural Partners LLC ("GAP") in connection with the above-referenced Prevention of Significant Deterioration ("PSD") Construction Permit application filed with the Iowa Department of Natural Resources ("IDNR") Air Quality Bureau ("AQB") on April 28, 2023, pursuant to Iowa Administrative Code 567—Chapter 33. The application seeks authorization for the construction of the Muscatine Expansion Facility ("MEF"), a greenfield soybean processing and specialty fertilizer blending facility to be located on a 147-acre site in Muscatine County, Iowa, at 14800 Highway 61 North, Muscatine, Iowa 52761 (Muscatine County Parcel ID 0735-19-200-004). As described in detail in the application, the MEF will comprise a soybean crush operation with a design capacity of 3,200 tons per day and a granular fertilizer blending line with a capacity of 450 tons per day.
We acknowledge receipt of AQB's completeness review comments, which were transmitted via electronic mail on or about May 10, 2023. In those comments, AQB identified three areas in which supplemental information is required before a completeness determination can be issued for the PSD application. Specifically, AQB requested additional detail concerning: (1) the AERMOD receptor grid spacing and configuration used in the air dispersion modeling analysis; (2) startup and shutdown emission estimates for emission units EU-01 and EU-02; and (3) supporting documentation for the proposed baghouse filter particulate matter outlet concentration specification for EU-04.
This letter provides GAP's responses to each of the three items identified by AQB, together with supplemental documentation and revised application materials as described herein. These responses have been prepared in coordination with Pinnacle Environmental Consultants Inc. ("Pinnacle"), GAP's environmental consultant, under the direction of Dr. Leonard Fisk, P.E., Principal of Pinnacle's Air Quality Practice, located at 1120 Ingersoll Avenue, Suite 210, Des Moines, Iowa 50309. Dr. Fisk has supervised the preparation of all technical analyses and supplemental materials enclosed with this response.
It is GAP's understanding, based on communications with your office, that upon satisfactory receipt of these supplemental materials, AQB anticipates issuing a completeness determination for the PSD application by May 19, 2023. GAP appreciates AQB's diligent review and is committed to providing all information necessary to facilitate a timely completeness determination and progression of the permitting process.
The responses to each of AQB's three comments are set forth below in the order in which they were raised in AQB's May 10, 2023 correspondence.
II. Response to Comment No. 1: AERMOD Receptor Grid Spacing and Configuration
A. Summary of IDNR Comment
In its completeness review comments, AQB requested additional detail regarding the receptor grid configuration used in the AERMOD air dispersion modeling analysis submitted as Appendix C to the PSD application. Specifically, AQB asked GAP to confirm and document: (i) the receptor grid spacing intervals from the facility fenceline outward to the maximum extent of the modeling domain; (ii) the maximum extent of the receptor grid in each cardinal direction; and (iii) the placement of discrete receptors at the nearest residential receptor location, including the distance and direction of that receptor relative to the proposed emission sources. AQB noted that while Appendix C contained modeling output files and graphical concentration plots, the receptor grid configuration narrative did not fully describe the grid spacing intervals and nesting approach used.
B. GAP Response
GAP and Pinnacle appreciate AQB's careful review of the AERMOD modeling documentation and are pleased to provide the following clarification and supplemental information in response to this comment.
The AERMOD air dispersion modeling analysis submitted with the PSD application was performed using AERMOD Version 23.1, which is the current regulatory version of the model approved by the U.S. Environmental Protection Agency ("EPA") for PSD and other New Source Review applications. The modeling was conducted in accordance with both IDNR's Air Dispersion Modeling Guidelines, as published by AQB, and EPA's Guideline on Air Quality Models, codified at Appendix W to 40 C.F.R. Part 51. GAP confirms the following receptor grid configuration details:
Cartesian Receptor Grid. The primary receptor grid is a Cartesian receptor grid with 50-meter spacing extending from the facility fenceline outward to a distance of 5 kilometers in all four cardinal directions. This grid encompasses a total modeling domain of approximately 10 kilometers by 10 kilometers centered on the facility, providing comprehensive spatial coverage for the purpose of identifying the location of maximum modeled concentrations for all criteria pollutants subject to the PSD review.
Nested Fine Grid. A nested finer-resolution Cartesian grid with 25-meter spacing was employed within the first 500 meters of the facility fenceline in all directions. This nested grid was implemented to provide enhanced spatial resolution in the near-field area surrounding the facility, where maximum ground-level concentrations are most likely to occur. GAP acknowledges that this detail was inadvertently omitted from the modeling protocol narrative included in Section C.2 of Appendix C to the application. The nested grid was, however, correctly implemented in the AERMOD input files that were submitted with the application, and the modeling results reflect the use of this finer-resolution grid. GAP regrets the oversight in the narrative description and has prepared a supplemental explanation that is included with the enclosed materials.
Discrete Receptors. Discrete (flagpole) receptors were placed at the nearest residential receptor location, which is situated approximately 0.42 miles (2,218 feet) east-northeast of the proposed primary stack location for emission unit EU-01. The discrete receptors were placed at a height of 1.5 meters above ground level, consistent with EPA guidance for representing breathing-zone height at residential locations. The coordinates and elevation of the nearest residential receptor were verified by Pinnacle using publicly available Muscatine County GIS parcel data and a field reconnaissance survey conducted on March 8, 2023.
Terrain Data. Terrain elevations were incorporated into the modeling analysis using U.S. Geological Survey ("USGS") National Elevation Dataset ("NED") data at 1/3 arc-second resolution (approximately 10-meter horizontal resolution). The terrain data were processed through the AERMAP terrain pre-processor (Version 18081) to generate receptor and source elevations and hill-height scale values for input into AERMOD. The terrain in the vicinity of the MEF site is generally flat to gently rolling, with elevation variations of approximately 30 feet across the modeling domain, which is characteristic of the Mississippi River valley terrain in Muscatine County.
Meteorological Data. The modeling analysis employed a 5-year meteorological dataset from the Muscatine Municipal Airport (station identifier KMUT), covering the period January 1, 2018, through December 31, 2022. Surface meteorological data from KMUT were paired with upper-air data from the Davenport, Iowa, National Weather Service station (station identifier KDVN), which is the nearest upper-air sounding station. The meteorological data were processed using the AERMET meteorological pre-processor (Version 22112) in accordance with both EPA and IDNR guidance, including the application of the Bulk Richardson Number approach for determining the planetary boundary layer height and the use of AERSURFACE (Version 21112) to characterize surface roughness, albedo, and Bowen ratio values for the land use surrounding the KMUT station.
Supplemental Receptor Grid Map. Enclosed herewith as Attachment A is a supplemental receptor grid map prepared by Pinnacle that depicts all Cartesian grid receptors (both the 50-meter primary grid and the 25-meter nested grid), discrete receptors at the nearest residential receptor location, and the facility property boundary. The map includes grid spacing annotations, a distance scale, and a north arrow. The map was prepared using GIS software and overlaid on current aerial photography of the project area for reference.
Dr. Fisk of Pinnacle has verified the receptor grid configuration and confirms that it is fully consistent with IDNR's Air Dispersion Modeling Guidelines and EPA's Guideline on Air Quality Models (Appendix W to 40 C.F.R. Part 51). The receptor grid provides adequate spatial resolution and geographic extent to identify maximum modeled concentrations at all ambient air locations, including the nearest residential receptor and the facility fenceline.
GAP also takes this opportunity to confirm that the maximum modeled impact results presented in the application remain unchanged as a result of this supplemental clarification. Specifically, the 24-hour PM₁₀ impact, which represents the highest modeled concentration relative to the applicable National Ambient Air Quality Standard ("NAAQS"), was determined to be 38.2 µg/m³ (modeled concentration) plus 72 µg/m³ (background concentration), for a total of 110.2 µg/m³. This total is well below the 24-hour PM₁₀ NAAQS of 150 µg/m³, providing a compliance margin of approximately 39.8 µg/m³. Similarly, all other criteria pollutant concentrations were demonstrated to be in compliance with the applicable NAAQS and PSD increments for all averaging periods.
Finally, GAP notes that Muscatine County is designated as attainment or unclassifiable for all criteria pollutants under the Clean Air Act, thereby confirming the applicability of the PSD permitting program and the PSD increment analysis. The increment consumption analysis presented in Appendix C of the application demonstrates that the MEF's emissions will not cause or contribute to a violation of any applicable PSD increment.
III. Response to Comment No. 2: Startup and Shutdown Emission Estimates for EU-01 and EU-02
A. Summary of IDNR Comment
AQB's second completeness review comment requested clarification of the emission estimates for EU-01, the natural gas-fired process heater rated at 120 MMBtu/hr heat input capacity, and EU-02, the soybean dryer rated at 80 MMBtu/hr heat input capacity and also fired on natural gas. Specifically, AQB noted that the application narrative and the emissions inventory presented in Table 4-2 of the application included only steady-state potential-to-emit ("PTE") figures calculated at maximum rated capacity and continuous operation (8,760 hours per year). AQB observed that the application did not separately quantify or discuss emissions during transient startup and shutdown operating periods for these two emission units. AQB asked GAP to clarify whether startup and shutdown emissions were included within the PTE calculations already presented, or whether startup and shutdown emissions represent additional emissions not accounted for in the application's emission inventory and PTE determinations.
B. GAP Response
GAP appreciates AQB's request for clarification on this point. The treatment of startup and shutdown emissions is an important aspect of the PTE determination, and GAP is pleased to provide the following detailed response, which has been prepared by Pinnacle in coordination with GAP's operations and engineering teams.
Basis for Steady-State PTE Calculations. The PTE calculations for EU-01 and EU-02 presented in Table 4-2 of the original application were based on maximum continuous steady-state operation at rated capacity — specifically, 120 MMBtu/hr for EU-01 and 80 MMBtu/hr for EU-02 — for 8,760 hours per year (i.e., continuous year-round operation). This methodology inherently represents a conservative, upper-bound estimate of annual emissions because it assumes both units operate at their maximum rated heat input capacity without interruption for the entire calendar year. In practice, of course, actual operations will include periods of reduced load, maintenance outages, and seasonal variations in production schedules, all of which would result in actual emissions below the calculated PTE values.
Startup and Shutdown Emissions Are Not Separately Additive. GAP clarifies that startup and shutdown emissions for EU-01 and EU-02 are not separately additive to the steady-state PTE figures reported in the application. This conclusion is based on the following technical considerations:
(a) Rapid Achievement of Stable Combustion. Both EU-01 and EU-02 are natural gas-fired combustion units that achieve stable combustion conditions rapidly upon ignition. Based on manufacturer specifications and operating experience with comparable equipment, the estimated startup duration is approximately 30 minutes per event for EU-01 and approximately 20 minutes per event for EU-02. During these brief startup periods, the units are operating at reduced firing rates, and emissions are therefore lower on a mass-per-hour basis than during steady-state maximum-rate operation.
(b) Reduced Firing Rates During Startup. During startup, burner firing rates for both EU-01 and EU-02 are maintained at reduced capacity, typically in the range of approximately 25% to 40% of rated heat input. Because the mass emission rates for criteria pollutants are directly proportional to the rate of fuel combustion, the reduced firing rates during startup result in lower mass emission rates (expressed in pounds per hour) than the maximum steady-state rates used in the PTE calculations.
(c) BACT Controls Operational During Startup. The low-NOₓ burners with flue gas recirculation ("FGR"), which constitute the proposed Best Available Control Technology ("BACT") for NOₓ control on EU-01 and EU-02, are operational during startup. GAP acknowledges that during the initial burner stabilization phase — estimated to last approximately the first 10 minutes of each startup event — NOₓ emission rates may be slightly elevated on a pounds-per-MMBtu basis relative to the steady-state BACT emission limit. Pinnacle estimates that the NOₓ emission rate during this initial stabilization phase is approximately 0.050 lb/MMBtu, which declines to the BACT limit of 0.036 lb/MMBtu upon full burner stabilization. This brief period of marginally elevated emission rates, combined with the reduced firing rate, results in only a negligible incremental contribution to annual emissions above the steady-state PTE.
(d) Negligible Shutdown Emissions. Shutdown emissions for both EU-01 and EU-02 are negligible. Both units undergo controlled ramp-down of the burner firing rate during shutdown, during which emissions decline in proportion to the decreasing fuel combustion rate. There is no period of elevated emissions during shutdown, and the controlled ramp-down process does not produce transient emission spikes.
Supplemental Startup/Shutdown Emission Calculations. Notwithstanding the foregoing, and to provide AQB with complete documentation, Pinnacle has prepared supplemental startup and shutdown emission calculations for EU-01 and EU-02. These calculations conservatively estimate the incremental emissions attributable to startup and shutdown events above the steady-state PTE basis, as follows:
EU-01 (Natural Gas-Fired Process Heater, 120 MMBtu/hr): GAP estimates approximately 12 startup events per year and 12 shutdown events per year for EU-01, based on the anticipated operating schedule, which includes planned maintenance outages and seasonal operational adjustments. Based on the startup emission profile described above (30-minute duration, 25–40% firing rate, 0.050 lb/MMBtu NOₓ during the first 10 minutes declining to 0.036 lb/MMBtu), Pinnacle calculates incremental startup NOₓ emissions of approximately 0.08 tons per year ("tpy") above the steady-state PTE. Incremental shutdown emissions are negligible and are estimated at less than 0.01 tpy NOₓ.
EU-02 (Soybean Dryer, 80 MMBtu/hr): GAP estimates approximately 24 startup events per year and 24 shutdown events per year for EU-02. The higher frequency of startup and shutdown events for EU-02 reflects the seasonal cycling of the soybean dryer in connection with soybean processing campaigns, which are driven by harvest schedules and market conditions. Based on the startup emission profile described above (20-minute duration, 25–40% firing rate, similar elevated lb/MMBtu rate during initial stabilization), Pinnacle calculates incremental startup NOₓ emissions of approximately 0.05 tpy above the steady-state PTE. Incremental shutdown emissions are negligible and are estimated at less than 0.01 tpy NOₓ.
Total Incremental Startup/Shutdown Emissions: The total incremental startup and shutdown NOₓ emissions for both EU-01 and EU-02 combined are approximately 0.13 tpy. This figure is well within the aggregate facility-wide PTE of 312 tpy NOₓ already reported in the application and represents approximately 0.04% of the total facility NOₓ PTE. The incremental startup/shutdown emissions are therefore de minimis and do not materially affect the facility's PTE, BACT determinations, NAAQS compliance demonstrations, or PSD increment consumption analyses.
Other Criteria Pollutants. Pinnacle has conducted a similar analysis for PM₁₀, PM₂.₅, carbon monoxide ("CO"), volatile organic compounds ("VOC"), sulfur dioxide ("SO₂"), and greenhouse gases ("GHG," expressed as CO₂-equivalent) during startup and shutdown of EU-01 and EU-02. This analysis confirms that transient startup and shutdown emissions for all of these pollutants are de minimis relative to the steady-state PTE and do not change the application's overall emission inventory, BACT determinations, NAAQS compliance demonstrations, or PSD increment consumption analyses. The detailed calculations are included in the revised Table 4-2 enclosed herewith.
Revised Table 4-2. Enclosed herewith as Attachment B is a revised Table 4-2 (Emission Summary) for the MEF. The revised table now includes a footnote and supplemental line items that separately quantify startup and shutdown emissions for EU-01 and EU-02 alongside the steady-state PTE figures. This revision is intended to provide AQB with a comprehensive and transparent accounting of all emissions, including transient operating modes, consistent with AQB's request for clarification.
GAP confirms that the aggregate facility-wide PTE figures reported in the original application remain valid and are unchanged by this supplemental analysis. The facility-wide PTE values are summarized as follows:
These PTE values continue to reflect the maximum potential emissions of the facility, inclusive of all emission units and operating modes, and serve as the basis for the BACT analysis, NAAQS compliance demonstration, and PSD increment consumption analysis presented in the application.
IV. Response to Comment No. 3: Baghouse Filter PM Outlet Specification for EU-04
A. Summary of IDNR Comment
AQB's third completeness review comment requested supplemental documentation supporting the proposed particulate matter ("PM") outlet concentration specification of 0.005 grains per dry standard cubic foot ("gr/dscf") for the baghouse filters controlling emissions from EU-04. Emission unit EU-04 encompasses material handling and storage operations at the MEF, including grain elevators, enclosed belt conveyors, storage bin venting, and fertilizer product loadout operations. AQB noted that the BACT analysis included in the application asserted a 99.5% control efficiency for the proposed baghouse system but did not provide vendor performance data, equipment design specifications, or references to comparable installations supporting the proposed outlet concentration of 0.005 gr/dscf. AQB requested that GAP submit such supplemental documentation to support the technical feasibility and achievability of the proposed emission limit.
B. GAP Response
GAP appreciates AQB's request for additional supporting documentation and is pleased to provide the following detailed response, together with the supplemental materials enclosed as Attachment C.
Description of EU-04. Emission unit EU-04 encompasses all particulate-generating material handling and storage operations at the MEF. Specifically, EU-04 includes the following sources:
• Grain receiving operations (truck dump and rail unloading pits)
• Bucket elevator legs (four units serving grain receiving, storage, and processing transfer points)
• Enclosed belt conveyors (six units connecting grain receiving, storage, processing, and loadout areas)
• Grain storage bin venting (eight storage bins with a combined capacity of approximately 2.4 million bushels)
• Fertilizer product storage bin venting (four bins with a combined capacity of approximately 12,000 tons)
• Fertilizer product loadout operations (truck and rail loadout via enclosed spouts with dust collection)
All of the foregoing sources are ducted to centralized pulse-jet fabric filter (baghouse) dust collection systems. The baghouse systems are designed and specified to serve as the primary PM control technology for all material handling and storage emission points within EU-04.
Proposed BACT Control and Specifications. GAP confirms that the proposed BACT control for EU-04 is pulse-jet fabric filter (baghouse) dust collection, with the following design and performance specifications:
• PM Outlet Concentration: 0.005 gr/dscf (approximately 11.4 mg/m³)
• Control Efficiency: 99.5%
• Air-to-Cloth Ratio: 4:1 (gross)
• Filter Media: Polyester felt with polytetrafluoroethylene ("PTFE") membrane laminate
• Cleaning Mechanism: Pulse-jet (compressed air) cleaning with on-demand differential pressure control
• Filter Bag Dimensions: Nominal 6-inch diameter by 120-inch length
The PTFE membrane laminate filter media provides superior particulate filtration performance compared to conventional woven or felted filter media, achieving high collection efficiency across a broad particle size distribution, including fine particulate matter (PM₂.₅). The membrane laminate creates a surface filtration mechanism that captures particulate on the outer surface of the membrane rather than allowing depth penetration into the filter media, resulting in consistently low outlet concentrations and high cleaning efficiency throughout the service life of the filter bags.
Supporting Documentation (Attachment C). In response to AQB's request, GAP has assembled and enclosed herewith as Attachment C the following supplemental documentation supporting the proposed 0.005 gr/dscf outlet concentration specification:
(1) Vendor Performance Guarantee Letter. Attachment C includes a performance guarantee letter from the baghouse equipment manufacturer, confirming that the proposed baghouse system is guaranteed to achieve a PM outlet concentration of 0.005 gr/dscf or less under the specified operating conditions, including the anticipated grain and fertilizer dust loading, air-to-cloth ratio, and volumetric flow rates. The performance guarantee is subject to standard commercial conditions, including proper installation, operation, and maintenance of the baghouse system in accordance with the manufacturer's specifications and recommendations.
(2) Equipment Specification Sheets. Attachment C includes detailed equipment specification sheets for the proposed baghouse units, showing all relevant design parameters, including overall dimensions, number of filter bags per unit, total filtration area, design volumetric flow rate, air-to-cloth ratio, filter media type and weight, cleaning cycle specifications (pulse duration, pulse pressure, cleaning interval), hopper design, and materials of construction. The specification sheets confirm that the equipment is designed and rated to achieve the proposed 0.005 gr/dscf outlet concentration at the air-to-cloth ratio of 4:1 specified in the application.
(3) Comparable Installation Stack Test Data. Attachment C includes a summary of stack test data compiled by Pinnacle Environmental from three comparable soybean processing and grain handling installations in Iowa and Nebraska where the same baghouse technology (pulse-jet fabric filter with PTFE membrane laminate filter media) has been installed and has achieved outlet concentrations at or below 0.005 gr/dscf during compliance stack testing. The three comparable installations, their locations, and the measured outlet concentrations are summarized as follows:
All three comparable installations utilize pulse-jet baghouse systems with PTFE membrane laminate filter media and air-to-cloth ratios in the range of 3.5:1 to 4.5:1, which are comparable to the design parameters proposed for the MEF. The stack test data demonstrate that the proposed 0.005 gr/dscf outlet concentration is readily achievable with this technology and represents a conservative (i.e., slightly higher than demonstrated) performance specification.
(4) RACT/BACT/LAER Clearinghouse References. Attachment C includes references to recent entries in EPA's RACT/BACT/LAER Clearinghouse ("RBLC") database for grain handling and processing facility PSD permits issued within the past five years. These RBLC entries demonstrate that outlet concentrations of 0.005 gr/dscf or lower have been established as BACT for baghouse-controlled grain handling and material storage operations at multiple facilities nationwide. The referenced RBLC entries confirm that the proposed 0.005 gr/dscf outlet specification is consistent with current BACT determinations for this source category and represents achievable, commercially proven technology.
Design Engineer Verification. GAP further confirms that Ridgeline Engineering Group LLC, the facility design engineer for the MEF, has incorporated the baghouse specifications described above into the MEF process and civil engineering design. Thomas Novak, P.E., Project Manager at Ridgeline Engineering Group LLC (7700 Pioneers Boulevard, Suite 105, Lincoln, Nebraska 68506), has verified the adequacy of the air-to-cloth ratio of 4:1 for the anticipated grain and fertilizer dust loading based on the design throughput capacities of the grain receiving, storage, conveying, and fertilizer blending and loadout systems. Mr. Novak has confirmed that the baghouse systems are properly sized and integrated into the facility design to maintain the specified air-to-cloth ratio and outlet concentration across the full range of anticipated operating conditions.
Consistency with Emission Inventory and Modeling. GAP notes that the 0.005 gr/dscf outlet specification, combined with the proposed 99.5% control efficiency, is reflected in the PM₁₀ PTE of 196 tpy and PM₂.₅ PTE of 87 tpy reported for the facility in the original application. These PTE figures formed the basis for the AERMOD air dispersion modeling analysis demonstrating compliance with all applicable NAAQS and PSD increments. No changes to the PM₁₀ or PM₂.₅ PTE figures, the BACT analysis, or the modeling results are required as a result of this supplemental documentation.
V. Enclosures and Attachments Summary
For AQB's convenience, GAP provides the following summary of all supplemental materials enclosed with this response:
Attachment A — Supplemental Receptor Grid Map. AERMOD receptor grid configuration map showing the 50-meter Cartesian receptor grid extending to 5 kilometers from the facility fenceline, the 25-meter nested receptor grid within 500 meters of the fenceline, and discrete receptors placed at the nearest residential receptor location (0.42 miles / 2,218 feet east-northeast of EU-01). The map includes grid spacing annotations, a distance scale, north arrow, facility boundary, and aerial photography basemap.
Attachment B — Revised Table 4-2: Emission Summary with Startup/Shutdown Emission Estimates for EU-01 and EU-02. Revised emission summary table incorporating footnoted line items that separately quantify startup and shutdown emissions for EU-01 and EU-02 alongside steady-state PTE figures. Aggregate facility-wide PTE values remain unchanged: NOₓ 312 tpy, SO₂ 28 tpy, PM₁₀ 196 tpy, PM₂.₅ 87 tpy, CO 245 tpy, VOC 164 tpy, and GHG (CO₂e) 148,600 tpy.
Attachment C — Supplemental Baghouse Documentation. Compilation of supporting documentation for the proposed 0.005 gr/dscf baghouse outlet concentration specification for EU-04, including: (i) vendor performance guarantee letter; (ii) equipment specification sheets; (iii) comparable installation stack test data summary (three Iowa and Nebraska facilities); and (iv) EPA RACT/BACT/LAER Clearinghouse references for recent grain handling and processing facility PSD permits.
Attachment D — Updated Stack-Parameter Spreadsheet. Revised electronic spreadsheet (Microsoft Excel format) containing corrected and updated stack parameters for all emission units EU-01 through EU-06, including stack height, stack inside diameter, exit velocity, exit temperature, and geographic coordinates (UTM Zone 15N, NAD83 datum). The spreadsheet has been updated to incorporate the clarifications and supplemental information provided in response to Comments 1 through 3 above.
VI. Request for Completeness Determination
Based on the foregoing responses and the enclosed supplemental materials, GAP respectfully requests that AQB review the submissions and issue a completeness determination for the PSD Construction Permit application at its earliest convenience. GAP understands, based on prior communications with AQB, that the completeness determination is anticipated by May 19, 2023, and GAP appreciates AQB's diligence in adhering to this timeline.
GAP notes that the project schedule for the MEF contemplates the commencement of the public notice and comment period promptly following issuance of the completeness determination, consistent with the permitting timeline previously discussed with AQB. Timely progression of the permitting process is important to GAP's construction schedule and to the broader project development timeline for the MEF.
GAP remains fully committed to meeting all applicable permitting requirements under the Clean Air Act, Iowa Administrative Code 567—Chapter 33, and all other applicable federal, state, and local regulations. GAP is available and prepared to provide any additional information that AQB may require in connection with the completeness review or the subsequent substantive review of the PSD application.
For the record, GAP has site control of the 147-acre project site identified by Muscatine County Parcel ID 0735-19-200-004, which was acquired from the Reinholt Family Trust on January 20, 2023, as previously documented in Section 2.1 of the application. Additionally, the Muscatine County Board of Supervisors approved Conditional Use Permit No. MC-2022-041 for the MEF on November 15, 2022, authorizing the proposed soybean processing and fertilizer blending use at the project site, as documented in Appendix A to the application.
VII. Availability and Contact Information
GAP and its counsel remain available to discuss these responses or provide any additional information at AQB's request. To facilitate efficient communication, GAP respectfully directs the following categories of inquiries to the appropriate points of contact:
Technical Questions regarding AERMOD air dispersion modeling, emissions calculations, startup/shutdown emission estimates, and baghouse specifications should be directed to:
Dr. Leonard Fisk, P.E. Principal, Air Quality Practice Pinnacle Environmental Consultants Inc. 1120 Ingersoll Avenue, Suite 210 Des Moines, Iowa 50309 Telephone: (515) 331-4200
Email: lfisk@pinnacle-env.com
Legal and Permitting Process Questions should be directed to the undersigned or to:
Rafael Dominguez Lead Associate Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 284-7618
Email: rdominguez@calderwoodharkness.com
GAP In-House Contact for this matter:
Derek Yun Director of Environmental, Health & Safety Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 492-3300
Email: dyun@greenfieldagpartners.com
VIII. Closing
We appreciate AQB's prompt review of the PSD application and the thoroughness of the completeness review comments. GAP looks forward to the completeness determination and to continuing to work cooperatively with AQB throughout the permitting process for the Muscatine Expansion Facility. Please do not hesitate to contact us if you have any questions regarding these responses or the enclosed supplemental materials.
Respectfully submitted,
CALDERWOOD & HARKNESS LLP
By: ________
Cynthia Ho Associate 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 284-7622
Email: cho@calderwoodharkness.com
cc: (via electronic mail)
Patricia Caldwell, General Counsel & VP of Regulatory Affairs, Greenfield Agricultural Partners LLC Derek Yun, Director of Environmental, Health & Safety, Greenfield Agricultural Partners LLC Margaret Solberg, VP of Operations, Greenfield Agricultural Partners LLC James Prentice, Partner, Calderwood & Harkness LLP Rafael Dominguez, Associate, Calderwood & Harkness LLP Dr. Leonard Fisk, P.E., Principal, Pinnacle Environmental Consultants Inc. Thomas Novak, P.E., Project Manager, Ridgeline Engineering Group LLC
Enclosures:
Attachment A — Supplemental Receptor Grid Map Attachment B — Revised Table 4-2 (Emission Summary with Startup/Shutdown Estimates) Attachment C — Supplemental Baghouse Documentation Attachment D — Updated Stack-Parameter Spreadsheet (Excel format)
Pollutant | Facility-Wide PTE (tpy)
NOₓ | 312
SO₂ | 28
PM₁₀ | 196
PM₂.₅ | 87
CO | 245
VOC | 164
GHG (CO₂e) | 148,600
Installation | Location | Year Tested | Measured PM Outlet (gr/dscf)
Heartland Grain Processing, LLC | Cedar Rapids, Iowa | 2021 | 0.0038
Platte Valley Ag Cooperative | Columbus, Nebraska | 2020 | 0.0042
Hawkeye Soy Products, Inc. | Iowa Falls, Iowa | 2022 | 0.0031

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