PERMIT RATIONALE FOR REISSUANCE
Tennessee Gas Pipeline Company LLC, Bay St Louis Compressor Station Number 530
Water NPDES No. MS0046230
Thomas Kelly, Water I Branch
April 16, 2025

I.	FACILITY INFORMATION

Facility Address:  10064 Lower Bay Road, Bay St. Louis, MS  39520 
Facility County:  Hancock
EPA ID:  110001471899
SIC:  4922

II.	NATURE OF BUSINESS

Transmission of natural gas

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

Outfall 001: The effluent discharge consists of compressor building drainage, air compressor condensate, wash down rack, equipment cleaning wash water, and storm water from the gas scrubber area and the electrical conduit manholes. The outfall has a maximum daily discharge flow of 0.0086 MGD and discharges into an unnamed ditch (7Q10 flow=0 cfs) then into Bryan Bayou, then into Bayou Caddy, then into Lake Borgne, and then into the Mississippi Sound. These streams are located in the Coastal Streams Basin. The Mississippi Sound is classified as “shellfish harvesting and recreation”, and the remaining streams are classified as “fish and wildlife”.

IV.	303(d) and TMDL ISSUES

There are no 303(d) issues. This permit complies with the following applicable TMDLs:

V.	TYPE OF WASTEWATER TREATMENT:

•	Oil/water separation 
•	Rock Reed filtration system.

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

None

VII.	DATA FROM APPLICATION FORM (2C)

Parameter	1Max. 	2LTA	3# 	
BOD5, mg/L	11.1	8.1	2	
COD, mg/L	86	54	2	
TOC, mg/L	38	33.4	2	
TSS, mg/L	18	17.5	2	
Ammonia, mg/L	0.2	0.2	2	
Flow, MGD	0.0086	0.0086	2	
Temperature (w), ºC	28.1	27.1	2	
Temperature (s), ºC	26.11	27.1	2	
pH, SU (max)	6.5	6.29	2	
Nitrate-Nitrite, mg/L	1.44	0.715	2	
Oil and Grease, mg/L	<3.0	<3.0	2	
Sulfate, mg/L	1.0	1.0	2	
Sulfite, mg/L	<3.0	<3.0	2	
Surfactants, mg/L	10	5.6	2	
1Max. = Maximum daily value
2LTA = Long-Term Average value
3# = Number of analysis

VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

	Not Applicable

IX.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

Not Applicable
 
X.	TOXICITY SCREENING

Not Applicable

XI.	PROPOSED FINAL LIMITATIONS 

1.	Average Permit Limitations
Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	1Basis	
001	Flow (MGD)	--	--	Report	Report	Twice per Quarter	Instantaneous Sampling	Quarterly	PPL, TJ	
001	Oil and Grease	--	--	10 mg/L	10 mg/L	Twice per Quarter	Grab Sampling	Quarterly	PPL, TJ	
001	pH (min.)	--	6.0 SU	6.0 SU	6.0 SU	Twice per Quarter	Grab Sampling	Quarterly	PPL, MSWQS	
001	Temperature, ºF	--	--	Report	Report	Twice per Quarter	Grab Sampling	Quarterly	PPL, TJ	

2.	Maximum Permit Limitations
Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	1Basis	
001	Flow (MGD)	--	--	Report 	Report	Twice per Quarter	Instantaneous Sampling	Quarterly	PPL, TJ	
001	Oil and Grease	--	--	15 mg/L	15 mg/L	Twice per Quarter	Grab Sampling	Quarterly	PPL, TJ	
001	pH (max.)	--	9.0 SU	9.0 SU	9.0 SU	Twice per Quarter	Grab Sampling	Quarterly	PPL, MSWQS	
001	Temperature, ºF	--	90 ºF	90 ºF	90 ºF	Twice per Quarter	Grab Sampling	Quarterly	PPL, MSWQS	

1Basis: MSWQS = Mississippi Water Quality Standards, TJ = Technical Judgement, PPL = Previous Permit Limits

XII.	BPJ STATEMENT: 

It is our judgment that the foregoing limitations represent technical judgment (TJ), and 423.12 11 Miss. Admin. Code Pt.6, Ch. 1 and Ch. 2 (MSWQS).