PERMIT RATIONALE FOR REISSUANCE
SABIC Innovative Plastics US LLC
Hancock County
Bay St. Louis, Mississippi
Water NPDES No. MSS062057
October 2025

I.	FACILITY INFORMATION

Facility Name:  SABIC Innovative Plastics US LLC
Facility Address:  3531 Port and Harbor Drive 
Bay St. Louis, MS 39520-9669
Bay St. Louis, 
Permit No.:  MSS062057
SIC:  2821
Permit Writer:  Samar Patel
EPD Branch:  Chemical Branch

II.	NATURE OF BUSINESS

The SABIC facility consists of two primary manufacturing units:  (1) the chem-ops production unit and (2) the finishing plant and miscellaneous support services.  The chem-ops unit manufactures styrene-acrylonitrile (SAN), acrylonitrile-butadiene-styrene (ABS), alpha-methyl styrene-acrylonitrile (AMSAN) and methyl methacrylate styrene-acrylonitrile (MMASAN).  The finishing plant produces plastic pellets.

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

Outfall 002:
Post-first flush storm waters from the Chem-Ops and STAMAX Plant areas, and other areas with minimal potential for storm water contamination are routed to the concrete drainage sump via the facility storm water ditch system.  Discharge into Mulatto Bayou.  

Outfall 003:
Storm waters falling within the curbed concrete sloped dock surface are routed to a collection pipe below the dock which gravity flows to a concrete containment sump at the shoreline.  The containment sump is equipped with a manual valve.  Discharge into Port Canal and thence to the Pearl River.  

Outfall 007:
Storm water runoff from the southeast firewater storage tank and pump area, former polypropylene ether (PPE) plant, outdoor storage of off-specification product (pig farm), equipment storage areas, maintenance, and truck/railcar loading and unloading areas.  Discharge into a drainage ditch, which flows to a Port Canal and thence to the Pearl River.

IV.	303(d) ISSUES

None

V.	TYPE OF WASTEWATER TREATMENT:

Outfall 002:
Equipped with a concrete collection sump upstream of outfall, where pH is monitored and automatically adjusted, if needed prior to discharge to Mulatto Bayou. 

Outfall 003:
Equipped with a concrete sump and a manual valve that allows collection of a sample for pH prior to discharge.

Outfall 007:
	None. 

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

Categorical guidelines only apply to Outfall 001A, which has a pretreatment permit.

VII.	DATA FROM APPLICATION FORM  (2F)

Outfall 002:
Parameter	Maximum Daily Value	
Oil and Grease	< 5.0 mg/L	
BOD5	< 6.8 mg/L	
COD	24 mg/L	
TSS	24 mg/L	
Total Nitrogen (TN)	5.7 mg/L	
Total Phosphorous (TP)	0.5 mg/L	
pH	7.42 s.u.	

Outfall 003:
Parameter	Maximum Daily Value	
Oil and Grease	< 5.0 mg/L	
BOD5	< 6.8 mg/L	
COD	11 mg/L	
TSS	< 5.0 mg/L	
Total Nitrogen (TN)	6.38 mg/L	
Total Phosphorous (TP)	0.50 mg/L	
pH	7.5 s.u.	

Outfall 007:
Parameter	Maximum Daily Value	
Oil and Grease	< 5.0 mg/L	
BOD5	< 6.8 mg/L	
COD	19.0 mg/L	
TSS	34 mg/L	
Total Nitrogen (TN)	20.1 mg/L	
Total Phosphorous (TP)	0.30 mg/L	
pH	8.17 s.u.	

VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

	Not applicable.

CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

Not applicable.

VIII.	TOXICITY SCREENING

Not applicable.

XI.	PROPOSED FINAL LIMITATIONS 

Permit Limitations

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Basis	
MS0036994-002	pH	n/a	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	MSWQS	
MS0036994-003	pH	n/a	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	MSWQS	
MS0036994-007	pH	n/a	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	6.0 to 9.0 s.u.	MSWQS	
MSWQS – Mississippi Water Quality Standard

All samples are monitored monthly when discharging.  pH is a grab sample and flow is an instantaneous sample.
 
Standard permit language requiring a Storm Water Pollution Prevention Plan (SWPPP) has been included, consistent with the requirements of Mississippi’s Baseline Storm Water General Permit.