PERMIT RATIONALE FOR ISSUANCE
Airgas USA LLC dba Airgas Dry Ice
Rankin County
Star, Mississippi
Water NPDES No. MS0062570
May 7, 2025

I.	FACILITY INFORMATION

Facility Name:  	Airgas USA LLC dba Airgas Dry Ice
Facility Address:  	217 Andrew Jackson Circle 
	Star, MS  39167    
Star, 
Permit No.:  		MS0062570
SIC:  			2813
Permit Writer:  	Tracy Tomkins
EPD Branch:  		Water I Branch

II.	NATURE OF BUSINESS

Airgas Dry Ice manufactures dry ice for use in food production facilities. The boxes are returned and rinsed.

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

Effluent form Outfall 001 consists of process wastewater from the rinsing of returned boxes from food processing facilities. Approximately 3,400 gpd will be discharged into an unnamed tributary (7Q10=0) of Steen Creek. This stream is located in the Pearl River Basin. 

IV.	TOTAL MAXIMUM DAILY LOAD (TMDL) AND 303(d) ISSUES

The receiving stream, Steen Creek, is not listed on the Mississippi 2018 Section 303(d) List of Impaired Water Bodies.

A Pearl River Basin TMDL for Total Nitrogen and Total Phosphorus for the Pearl River was approved in June of 2009. This discharge is considered a de minimis flow and complies with the Pearl River Nutrient TMDL. 

V.	TYPE OF WASTEWATER TREATMENT

Bag Filtration, granular activated carbon polishing, and pH adjustment.

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

None.

VII.	DATA FROM APPLICATION FORM 2C

Parameter	Maximum Daily Value	
Flow	0.0033 MGD	
BOD5	10 mg/l	
Chlorine	<0.050 mg/l	
pH	8.76 SU	
TSS	8.7 mg/l	
Ammonia-N	<0.10 mg/l	
Phosphorus	1.9 mg/l	
Fecal Coliform	<100 CFU/100 ml	

VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

Due to the characteristics of the effluent, the discharge from this facility cannot be modeled.  As such, the Water Quality Modeling and TMDL Branch cannot provide WQBELs. Recommend compliance with categorical limitations and water quality standards.

IX.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

Not Applicable.

X.	TOXICITY SCREENING

Not Applicable.

XI.	PROPOSED FINAL LIMITATIONS 

1.	Average Permit Limitations

Parameter	Categorical Limitation	Current Permit Limitation	Proposed Permit Limitation	Basis	
Ammonia Nitrogen, Total	N/A	1 mg/l	Report, mg/l	EJ	
Oxygen Demand (CBOD5)	N/A	10 mg/l	30 mg/l	DG	
Total Nitrogen	N/A	Report lbs/day	Report lbs/day	CPL	
Total Phosphorus	N/A	Report lbs/day	Report lbs/day	CPL	
Dissolved Oxygen (DO)	N/A	6.0 mg/l min.	6.0 mg/l min.	CPL	
Flow, MGD	N/A	0.001 MGD	0.003 MGD	EJ	

2.	Maximum Permit Limitations

Parameter	Categorical Limitation	Current Permit Limitation	Proposed Permit Limitation	Basis	
Ammonia Nitrogen, Total	N/A	1.5 mg/l	Report, mg/l	EJ	
Oxygen Demand (CBOD5)	N/A	15 mg/l	45 mg/l	DG	
Total Nitrogen	N/A	Report lbs/day	Report lbs/day	CPL	
Total Phosphorus	N/A	Report lbs/day	Report lbs/day	CPL	
Flow, MGD	N/A	Report, MGD	Report, MGD	CPL	
pH	N/A	6.0 - 9.0 SU	6.0 - 9.0 SU	CPL	

EJ = Engineering Judgement, DG = Domestic Guidelines, CPL = Current Permit Limit. 

All parameters are to be sampled once/month, except for Total Nitrogen and Phosphorus which will be sampled once/quarter. 

Ammonia Nitrogen, CBOD5, Total Nitrogen, and Total Phosphorus sample type is 24hr composite. All other parameters are grab with the exception of flow which will be monitored by a totalizer.

Within 180 days of commencing discharge, the permittee shall submit to MDEQ a complete Form 2C.  Based upon the results of the sampling, the permit may be reopened to address additional limits or requirements as deemed necessary to protect water quality.