DRAFT PERMIT REVIEW SUMMARY

Permit Writer:	Thomas Parker	Date:	November 4, 2025

Company Name:	Mississippi Export Railroad Company, Mark B. Miller Railcar Repair Shop

Facility Location:	11458 Saracennia Road
Moss Point, MS 39562

Source Number:	1280-00150

County: 		Jackson

FACILITY DESCRIPTION

Mississippi Export Railroad Company, Mark B. Miller Railcar Repair (MSERR) is proposing to construct a railroad spur and building, which will contain repair (cutting and welding), abrasive blasting, and painting operations to make needed repairs to railcars that have been taken out of service. MSERR process operations will generate particulate matter (PM), particulate matter less than 10 microns (µm) in diameter (PM10), particulate matter less than 2.5 µm in diameter (PM2.5), volatile organic compounds (VOCs), sulfur oxides (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and hazardous air pollutants (HAPs). PM, SO2, NOx, CO, and VOC emissions will predominantly emit from the facility’s fuel burning equipment. MSERR operations fall under Standard Industrial Classification (SIC) Code 4789 (Transportation Services, Not Elsewhere Classified) and North American Industry Classification System (NAICS) 488210 (Support Activities for Rail Transportation. The proposed emission points at the facility are listed in the table below:

Emission Point	Description	
AA-000	Facility-Wide (Mississippi Export Railroad Company, Mark B. Miller Railcar Repair Shop)	
AA-001	Abrasive Blast Booth equipped with one (1) dust collector	
AA-002	Welding/Cutting Operations	
AA-003	Paint Booth equipped with dry filters	
AA-004	Paint Kitchen (Paint Storage exhausted to ambient air)	
AA-005	Fuel-Burning Equipment
•	Three (3) 0.067 MMBtu/hr Natural Gas-Fired Unit Heaters
•	Six (6) 1.02 MMBtu/hr Natural Gas-Fired Infrared Space Heaters	
AA-006	One (1) 6.05 MMBtu/hr Roof-Mounted Air Make-Up Unit                                                                  (Fuel Type: 1,050 Btu/scf Natural Gas, 94,986 Btu/gal Propane)	
AA-007	18,000-gallon Liquid Propane Gas (LPG) Storage Tank	

PROJECT/PERMIT ACTION DESCRIPTION

MSERR was given pre-permit construction approval as a Title V source on November 6, 2025.

Operations at the facility include the following processes:  

•	Abrasive Blast Booth (Emission Point AA-001): MSERR will operate one (1) Abrasive Blast Booth for up to two (2) eight (8) hour per shifts per day. Emission Point AA-001 will be equipped with an exhaust plenum that exhausts to a 27,000 cubic feet per minute (cfm) dust collector for PM control. The booth will also be equipped with two (2) #6 blasting nozzles rated at 100 pounds per square inch (psi) each. One (1) nozzle will have the capacity to use up to 1,200 pounds per hour (lb/hr) of steel grit, equivalent to 1.2 tons per hour (tph) and one (1) railcar blasted per shift. The steel grit will be recycled and reused as much as possible. The booth will have a bucket elevator used to fill a 300 cubic foot storage hopper to store the steel grit. The hopper will feed a 6.5 cubic foot blast pot. The bucket elevator will be piped to the dust collector for PM control. 

•	Welding/Cutting Operations (Emission Point AA-002): MSERR will use cutting torches and compressed air to remove the damaged sections of the railcar. Four (4) Millermatic electric Mig welders will be used to reinstall pieces of steel to the removed sections.

•	Paint Booth (Emission Point AA-003): MSERR will operate one (1) paint booth for up to two (2) eight (8) hour shifts per day. The booth will be equipped with two (2) 29,000 cfm exhaust plenum fans, dry filters, and one (1) 6.05 MMBtu/hr Roof-Mounted Air Makeup Air Unit (AA-006). Approximately 115 gallons of paint will be used per week to paint up to five (5) railcars per week. The booth will also be equipped with two (2) airless spray guns that are estimated to have 10% overspray.

•	Paint Kitchen (Emission Point AA-004): The paint kitchen will be utilized to store small amounts of the paints being used during the shift to paint the repaired railcar(s). Containers of varying sizes (i.e. 5 gallons, etc.) will be kept in the paint kitchen until used. Spent containers will be properly disposed of according to federal and state regulations. The paint kitchen will be equipped with a 1,300-cfm exhaust fan that will exhaust to ambient air.

•	Fuel-Burning Equipment (Emission Points AA-005 and AA-006): Fuel burning equipment utilized at the MSERR facility includes (3) natural gas-fired unit heaters with a capacity of 0.067 million British Thermal Units per hour (MMBtu/hr) each (Emission Point AA-005), six (6) natural gas-fired infrared radiant heaters with a capacity of 0.167 MMBtu/hr each (Emission Point AA-005), and one (1) 6.05 MMBtu/hr roof-mounted air make-up unit (Emission Point AA-006). Emission Point AA-006 will be mounted on the Paint Booth (Emission Point AA-003) and primarily combust natural gas but have the capability to combust propane as a backup fuel as needed.

•	Liquid Propane Gas (LPG) Storage Tank (Emission Point AA-007): One (1) 18,000 WGC LPG storage tank will be located on site to use as backup fuel to natural gas as needed. The tank will be equipped with two (2) 320 gallon per hour (gph) vaporizers.

EMISSION SUMMARY

Facility-Wide Potential Emission Summary
Pollutant	New Construction Potential Emissions
(tpy)	
PM/PM10/PM2.5	45.04	
SO2	0.02	
NOx	3.09	
CO	2.39	
VOC	105.76	
Toluene	31.48	
Total HAPs	31.54	

The potential facility-wide emissions for MSERR exceed the Title V major source thresholds of 100 tons per year (tpy) for VOCs, 25 tpy for Total HAPs, and 10 tpy for Individual HAPs (i.e. toluene). Therefore, the facility will be classified as a Title V major source and need to obtain an operating permit after the initial construction permit. MSERR is not listed as one of the 28 industrial categories where the Prevention of Significant Deterioration (PSD) emission threshold is reduced from 250 tpy to 100 tpy for any regulated criteria pollutant. Since the facility’s potential-to-emit for all criteria pollutants are significantly less than 250 tpy, the facility is not defined as a major source with respect to PSD and will not have any PSD avoidance limitations.

APPLICABLE/PROPOSED PERMIT LIMITATIONS

Facility-Wide:
•	11 Miss. Admin. Code Pt. 2, R. 1.3.A. and 1.3.B.
o	Shall not cause, allow, or permit the emission of PM such that the opacity exceeds 40%. However, during startup operations, the source may exceed the 40% opacity requirement for up to fifteen (15) minutes per startup in any one-hour, not to exceed three (3) startups per 24-hour period.

•	11 Miss. Admin. Code Pt. 2, R. 1.3.C.
o	Shall not cause, allow, or permit the emission of particles or any contaminants in sufficient amounts, or of such duration from any process as to be injurious to humans, animals plants, or property, or to be a public nuisance, or create a condition of air pollution.

•	11 Miss. Admin. Code Pt. 2, R. 1.3.F(1).
o	Particulate and ash limited by the relationship E = 4.1 × p0.67, where “E” is the emission rate in pounds per hour, and “p” is the process weight input rate in tons per hour.

NSPS APPLICABILITY

40 CFR 60, Subpart Dc (Standards of Performance for Small Industrial-Commercial-Institutional Steam Generating Units):

Subpart Dc applies to facilities with industrial steam generating units with a rated capacity equal to or greater than 10 MMBtu/hr, but less than 100 MMBtu/hr, and installed, modified, or reconstructed after June 9, 1989. Emission Points AA-005 and AA-006 are between the applicable rated capacity, but the fuel-burning equipment is used for heating purposes and does not generate steam. Therefore, Emission Points AA-005 and AA-006 are not subject to 40 CFR 60, Subpart Dc.

40 CFR 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 each storage vessel for which construction, reconstruction, or modification commenced after October 4, 2023. Storage vessels with a capacity greater than or equal to 20,000 gallons (75.7 m3) but less than 40,000 gallons (75.7 m3) containing a volatile organic liquid (VOL) that, as stored, has a maximum true vapor pressure greater than or equal to 1.5 psia (10.3 kPa). Emission Point AA-007 has a maximum capacity of 18,000 gallons; therefore, MSERR is not subject to 40 CFR 60, Subpart Kc.

MACT APPLICABILITY

40 CFR 63, Subpart MMMM (National Emission Standards for Hazardous Air Pollutants for Surface Coating of Miscellaneous Metal Parts and Products): 

Subpart MMMM applies to facilities that apply coatings to miscellaneous metal parts and products that include, but is not limited to, metal components of the following types of products as well as the products themselves: motor vehicle parts and accessories, bicycles and sporting goods, recreational vehicles, extruded aluminum structural components, railroad cars, heavy duty trucks, medical equipment, lawn and garden equipment, electronic equipment, magnet wire, steel drums, industrial machinery, metal pipes, and numerous other industrial, household, and consumer products. A source is considered a new source if it is constructed after August 13, 2002. A new source is subject to Subpart MMMM if the facility uses 250 gallons (946 liters) per year, or more, of coatings that contain HAPs. Since MSERR is a major source of HAPs, the facility is subject to 40 CFR 63, Subpart MMMM.

Under Subpart MMMM, a control device is equipment that reduces the mass of HAP emissions to the atmosphere. Emission Point AA-003 is equipped with dry filters to reduce PM emissions. Therefore, Emission Points AA-003 and AA-004 have been permitted based on not having control devices.

40 CFR 63, Subpart XXXXXX (National Emission Standards for Hazardous Air Pollutants Area Source Standards for Nine Metal Fabrication and Finishing Source Categories):

Subpart XXXXXX applies to facilities that are “primarily engaged” in the operations in one of the nine following source categories:

1.	Electrical and Electronic Equipment Finishing Operations;
2.	Fabricated Metal Products;
3.	Fabricated Plate Work (Boiler Shops);
4.	Fabricated Structural Metal Manufacturing;
5.	Heating Equipment (except Electric);
6.	Industrial Machinery and Equipment Finishing Operations;
7.	Iron and Steel Forging;
8.	Primary Metal Products Manufacturing; and 
9.	Valves and Pipe Fittings.

The facility SIC Code 4789 (Transportation Services, Not Elsewhere Classified) is not listed as a subject source; therefore, MSERR is not subject to 40 CFR 63, Subpart XXXXXX.

40 CFR 63, Subpart HHHHHH (National Emission Standards for Hazardous Air Pollutants: Paint Stripping and Miscellaneous Surface Coating Operations at Area Sources):

Subpart HHHHHH establishes operation limitations and work practice standards for the spray application of coatings containing compounds of chromium (Cr), lead (Pb), nickel (Ni), or cadmium (Cd), collectively referred to as the target HAP, in concentrations greater than 0.1 percent by mass, or manganese (Mn) greater than 1.0 percent by mass. The coating must be applied to any part or product made of metal or plastic, or combinations of metal and plastic that are not motor vehicles or mobile equipment located at an area source of HAPs. MSERR is a major source of HAPs; therefore, the facility is not subject to 40 CFR 63, Subpart HHHHHH.

PUBLIC PARTICIPATION

The 30-day public notice period began on May 13, 2026, when the notice was posted on MDEQ’s website and ends June 12, 2026.