PERMIT REVIEW SUMMARY

Permit Writer:	Audra Sandifer 	Date:	January 28, 2025

Company Name:	Amazon Data Services Inc, JAN200

Facility Location:	1626 County Line Road, Ridgeland, MS 39157

Source Number:	1720-00099

County: 		Madison

FACILITY DESCRIPTION

Amazon Data Services, Inc (Amazon) has submitted a complete air application for a Permit to Construct Air Emissions Equipment. Amazon is proposing to construct a greenfield data processing facility in Ridgeland (Madison County), Mississippi. Amazon’s operations fall under SIC code 7374: Computer Processing and Data Preparation and Processing Services.

The site is referred to as the JAN200 Site (Site). The Site will include 391 emergency backup electrical power generator engines in various sizes with a total power generation capacity of 1,056 Megawatts (MW). The emergency backup generator engines will consist of:

•	Three-hundred and eighty-four (384) 2,750-Kilowatt (kW) Critical Emergency Backup Electrical Power Generator (CEG) Engines.
Each engine will consist of a 4,043-Horsepower (HP) Caterpillar 3516E Compression Ignition (CI) diesel-fired Tier-2 certified emergency generator engine, equipped with SCR, DOC, and DPF to meet Tier 4 equivalent emission limits.

•	Four (4) 750-kW House Emergency Backup Electrical Power Generators (HEG) Engines.
Each engine will consist of a 1,112 HP Caterpillar C18 CI diesel-fired Tier-2 certified emergency generator engine.

•	Two (2) 400-kW Building (Logistics Building and Administration Building) Emergency Backup Electrical Power Generators Engines.
Each engine will consist of a 609 HP Caterpillar C13 CI diesel-fired Tier-3 certified emergency generator engine.

•	One (1) 250-kW Security Building Emergency Backup Electrical Power Generator Engine.
A 398 HP Caterpillar C9 CI diesel-fired Tier-3 certified emergency generator engine.

The Site will have a total of 14 data center buildings (Building No. 1 – 14). Buildings No. 1 – 4, will contain 26 CEGs and 1 HEG. Buildings No. 5 – 14 will contain 28 CEGs. Since construction of the Site will be staged and emission sources will likely be installed over the course of years, emission sources have been grouped in the permit according to building number, as it is expected that upon each building’s construction will be followed by installation of the emergency generators in that building. 

Each emergency generator engine will be equipped with an associated diesel fuel storage tank. In addition to the belly tanks, the Site will also have fourteen (14) bulk diesel fuel storage tanks, with a volume capacity of 12,000 gallons each.

PROJECT/PERMIT ACTION DESCRIPTION

The permitting action is to issue the initial Permit to Construct of Air Emissions Equipment to Amazon Data Services, Inc.

EMISSION SUMMARY

Pollutant	PTE Emissions (tons/yr)	
Particulate Matter (TSP)	12.89	
PM10	12.89	
PM2.5	12.89	
Sulfur Dioxide (SO2)	1.21	
Nitrogen Oxides (NOx)	249.0	
Carbon Monoxide (CO)	249.0	
Volatile Organic Compounds (VOC)	28.62	
Total Reduced Sulfur (TRS)	—	
Lead	Not Listed	
CFC/HCFC	—	
Total HAP 	24.0	
1 The PTE emissions reflect any emission limits or enforceable restrictions included in the proposed permit.

APPLICABLE/PROPOSED PERMIT LIMITATIONS

Each of the critical emergency generators CEG 1 – 384 (Model CAT 3516E, 2,750 kW each) will be equipped with a selective catalytic reduction (SCR) unit, diesel oxidation catalyst (DOC), and diesel particulate filter (DPF) to meet Tier 4 equivalent emission limits. The three (3) control devices will be installed as one (1) individual control unit on each engine. The purpose of the control devices is for the Site to avoid exceeding major source PSD permitting. 

The final manufacturer for the control systems for the CEG engines has not yet been finalized. The control systems will be either be manufactured by Caterpillar, Miratech, or Safety Power. Or the control systems for the 384 CEG engines may be a combination of the three (3) manufacturers. Each proposed manufacturer’s provided control efficiencies of each system are provided below. 

Pollutant	Miratech Provided
Control Efficiency	Safety Power Provided Control Efficiency	Caterpillar Provided Control Efficiency	
NOx	91.7%	91.9%	91.7%	
CO	70%	80%	75%	
NMHC or VOC	50%	60%	45%	
Filterable PM	68.6%	75.6%	68.6%	

The post-controlled potential emissions from the Site are conservatively calculated based on the lowest control efficiency among the three (3) control system options for each pollutant. Amazon requests to retain flexibility to select either control system model or more than one model for installation throughout the Site. Final specifications of each engine’s selected control system will be detailed in each engine’s forthcoming certification of construction.

Performance stack testing is required within 180 days of startup for 36 engines. Subsequent testing shall be conducted every 5 years.  The testing shall be performed on this schedule until all engines in Emission Points AB-000 through AO-000 are tested. Testing shall be conducted according to:

(a)	Twelve (12) RICE equipped with Miratech control systems shall be tested.
(b)	Twelve (12) RICE equipped with Safety Power control systems shall be tested.  
(c)	Twelve (12) RICE equipped with Caterpillar control systems shall be tested.

Since Amazon requests to retain flexibility to select either control system model or more than one model for installation throughout the Site, MDEQ recognizes that the schedule denoted above may change. As Amazon submits final specifications of each engine’s selected control system will be detailed in each engine’s forthcoming certification of construction, MDEQ may re-open the permit to adjust RICE stack testing schedules due to potential changes in control systems.

As described in the NSPS Applicability section below, each emergency engine at the Site is limited to 100 hours per year of operation for readiness and/or maintenance testing, including non-emergency service. However, were each engine to operate 100 hours for purposes of readiness and/or maintenance testing, PSD emission thresholds for NOx and CO would be exceeded. When operating for purposes of readiness and/or maintenance testing, engines are operated under “No Load” conditions; therefore, the engine control devices do not meet their stated control efficiencies due to decreased engine exhaust temperature. Stated control efficiencies will only be met when engines are operated for emergency purposes at full engine load conditions. Therefore, in order to monitor and record monthly and rolling, consecutive twelve-month NOx and CO emissions, several variables must be recorded during each engine’s operation.

Each CEG engine will be equipped with a control system that will continuously measure and record the following:
•	The SCR catalyst bed exhaust temperature. The information will be recorded at a minimum frequency of once every minute, and correlated to run date, engine load/kilowatt output, and engine operating hours.
•	The NOx emissions measured after the catalyst, expressed in ppm. The information shall be recorded at a minimum frequency of once every minute, and correlated to run date, engine load/kilowatt output, and engine operating hours.
•	The differential pressure drop across the entire emissions control system to demonstrate proper function of the SCR, DPF, and DOC. The backpressure monitor shall notify the permittee when the high backpressure limit of the engine is approached. The emissions control system shall be observed by the permittee with a frequency as recommended by the process/control equipment manufacturer.

Further, each monitoring device will be equipped with a mechanism to detect parameters which exceed manufacturer’s recommended thresholds and trigger an alarm to operators when the unit is not operating within the manufacturer’s recommended conditions.

For CO emissions, the facility will apply the uncontrolled emission factor for any runtime that the catalyst bed is not within the manufacturer’s recommended range for control.

Following each month, total monthly NOx and CO emissions will be tabulated on a monthly and for each consecutive twelve-month period on a rolling basis.

PSD Applicability

Amazon is not one of the 28 categorical facilities listed in 40 CFR 52.21(b)(1)(i)(a); therefore, the PSD threshold for a major source is 250 tpy.  Amazon has the potential to emit more than 250 tons per year (tpy) of the following regulated NSR pollutants: nitrogen oxides (NOx) and carbon monoxide (CO). However, Amazon is proposing to limit facility-wide emissions of NOx and CO to 249.0 tpy, each; therefore, the facility will be considered a moderate stationary source. With potential emissions calculated based on each engine operating 100 hours per year, NOx is the only pollutant with potential emissions greater than 250 tpy. However, with potential emissions calculated based on each engine operating 500 hours per year, CO emissions also exceed 250 tpy.

Title V Source Applicability
Amazon’s potential-to-emit (PTE) exceeds the Title V major source threshold of 100 tons per year (tpy) for each of the following criteria air pollutants: Nitrogen Oxides (NOx) and Carbon Monoxide (CO). The facility’s potential-to-emit hazardous air pollutants (HAPs) does exceed the Title V major source thresholds of 25 tpy of total HAPs and 10 tpy for numerous individual HAPs. However, the facility will operate as an area source by taking federally enforceable limits for individual HAPs and total HAPs. 

NSPS APPLICABILITY

40 CFR Part 60, Subpart IIII—Standards of Performance for Stationary Compression Ignition Internal Combustion Engines
Subpart IIII applies to owners and operators of stationary compression ignition (CI) internal combustion engines (ICE) that commence construction (i.e. date the engine is ordered by the owner or operator) after July 11, 2005, and manufactured as a certified National Fire Protection Association (NFPA) fire pump engine after July 1, 2006. 

The 384 CEG 2,750-kW Genset diesel-fired emergency engines and 4 HEG 750-kW diesel-fired Genset emergency engines are each CI ICE and are subject to Subpart IIII. Each purchased engine must be certified to the emission standards in 40 CFR 60.4205(b) and Tier 2 of Appendix I of 40 CFR 1039, which include: 6.4 grams per kilowatt-hour (g/kW-hr) of Nitrogen Oxides (NOx) emissions; 3.5 g/kW-hr of Carbon Monoxide (CO) emissions; and to 0.2 g/kW-hr of Particulate Matter (PM) emissions.

The 2 400-kW Genset diesel-fired emergency engines and 1 250-kW Genset diesel-fired emergency engine are each CI ICE and are subject to Subpart IIII. Each purchased engine must be certified to the emission standards in 40 CFR 60.4205(b) and Tier 3 of Appendix I of 40 CFR 1039, which include: 4.0 grams per kilowatt-hour (g/kW-hr) of Nitrogen Oxides (NOx) emissions; 3.5 g/kW-hr of Carbon Monoxide (CO) emissions; and to 0.2 g/kW-hr of Particulate Matter (PM) emissions.

Each emergency backup generator engine must also meet the operating and emergency operational requirements of 40 CFR 60.4211(a)-(f).

40 CFR Part 60, Subpart JJJJ—Standards of Performance for Stationary Spark Ignition Internal Combustion Engines
Subpart JJJJ applies to owners and operators of stationary spark ignition (SI) internal combustion engines (ICE) that commence construction (i.e. date the engine is ordered by the owner or operator) after June 12, 2006, and are manufactured on or after January 1, 2009, for emergency engines with a maximum engine power greater than 19 KW (25 HP). All emergency engines are CI engines. Therefore, Subpart JJJJ is not applicable.

40 CFR Part 60, Subpart Kc—Standards of Performance for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which Construction, Reconstruction, or Modification Commenced After October 4, 2023
Subpart Kc applies to any storage vessel with a capacity greater than or equal to 75.7 m3 (20,000 gal) that is used to store volatile organic liquids (VOL) for which construction, reconstruction, or modification is commenced after October 4, 2023. Amazon is proposing to construct a total of three hundred and ninety-one (391) diesel fuel storage tanks. Each tank will have a capacity of much less than 20,000 gallons; therefore, Subpart Kc is not applicable. 

MACT APPLICABILITY

40 CFR Part 63, Subpart ZZZZ—National Emissions Standards for Hazardous Air Pollutants for Stationary Reciprocating Internal Combustion Engines
Subpart ZZZZ applies to owners or operators of stationary reciprocating internal combustion engines (RICE) at area and major sources of HAP emissions. 

Each proposed diesel-fired emergency generator engine is considered ‘new stationary RICE’, as defined in 40 CFR 63.6590(a)(2)(iii), at an area source of HAP emissions. As such, each engine must meet the requirements of 40 CFR 63, Subpart ZZZZ by meeting the requirements of 40 CFR 60, Subpart IIII, for CI engines.  No further requirements apply for such engines under 40 CFR 63, Subpart ZZZZ or the General Provisions in Subpart A

PUBLIC PARTICIPATION

The 30-day public notice period began on March 5, 2025, with the publication of a notice MDEQ website and ends April 4, 2025.
RECOMMENDATION

The staff has preliminarily decided to recommend issuance of the permit to the Mississippi Environmental Quality Permit Board as shown in the draft permit.  However, the staff recommendation to the Board will be made only after a thorough consideration of all public comments.