PRETREATMENT RATIONALE FOR ISSUANCE

Entergy Mississippi LLC, Vicksburg Advanced Power Station
Warren County
Vicksburg, MS
Agency Interest (AI) No. 1074

	MSP092485
SIC: 4911
March 18, 2026
Permit Engineer: Tracy Tomkins
Water I Branch
	
I.	FACILITY INFORMATION

A.	Nature of Business: Electric Power Generation
B.	Process Wastewater Description: Ultrafiltration reject water, reverse osmosis reject water, service water and power block contact stormwater, HRSG blowdown
C.	Proposed Flowrate: 0.290 MGD (estimated)
D.	Applicable Federal Guidelines: None. Non-categorical Industry - SIU

II.	RECEIVING POTW INFORMATION

A.	POTW and Permit Number: Vicksburg POTW (AI# 13434, MS0022381)
B.	POTW Treatment Type: Biological by means of trickling filter followed by chlorine disinfection.
C.	POTW Design Flowrate: 10 MGD
D.	POTW Receiving Stream: Mississippi River
E.	POTW Receiving Stream 7Q10 (Q7/10): 127000 cfs

III.	NOTABLE SAMPLING DATA FOR PERMIT APPLICATION:  (Form 2P)

1Because this facility has not been constructed; the facility has utilized effluent characteristics from a similar facility to estimate the above pollutant concentrations. 

IV.	PROPOSED PERMIT LIMITATIONS

Outfall 001

Parameter	Monthly Avg	Daily Max	Minimum	Monthly Avg	Daily Max	Sampling Frequency	Sample Type	Basis of Decision1	
Flow	Report MGD	Report MGD	---	---	---	Continuously	Continuous Recorder	TJ	
Temperature 	---	---	---	Report ºF	Report ºF	Twice per month	Instantaneous Sampling	TJ	
pH	---	---	6.0 SU	---	9.5 SU	Twice per month	Grab sampling	TJ	
1Basis:  TJ = Technical Judgment

Other Permit Requirements

•	Submit DMRs to the City of Vicksburg:

The permittee shall submit the monthly Discharge Monitoring Report (DMR) to the City of Vicksburg via email (Edward.Busby@inframark.com). The DMR submission shall be done through the MDEQ NetDMR system due no later than the 28th day of the month following the completed reporting period. The DMR recipient's email address (Edward.Busby@inframark.com) should be added in the "DMR Submission Notification" section of NetDMR [11 Miss. Admin. Code Pt. 6, R. 1.1.4.A(4)].  

•	Application Submittal Requirement:

Within 6 months (180 days) of commencing discharge of effluent associated with normal power generation activities, the permittee shall submit to the MDEQ Environmental Permits Division a completed Form 2P application containing results of data collected from the facility's process wastewater discharge. The sampling data shall be representative of normal power generation activities. Based upon the results of the sampling, the permit may be reopened to address additional limits or requirements as deemed necessary to protect the POTW or water quality. The permittee shall submit the application within six months (180 days) of commencing discharge of effluent. [11 Miss. Admin. Code Pt. 6, R. 1.1.4.A(4)]

X.	STATEMENT OF BASIS 

 Technical Judgement 

APPENDIX A

ADEQUACY OF TREATMENT

Vicksburg POTW MS0022381

	Design Flowrate 10 MGD
				
	Average flow from DMRs January 2025- December 2025 = 2.84 MGD

	10.0 MGD – 2.839 MGD = 7.161 MGD capacity

	Proposed discharge to POTW 0.290 MGD
		
	7.161 MGD > 0.290 MGD, therefore the hydraulic capacity is adequate

Changes to second draft permit

(1)	Increased pH maximum limit to 9.5 s.u.

(2)	Updated additional requirements:

Application Submittal Requirement:

Within 6 months (180 days) of commencing discharge of effluent associated with normal power generation activities, the permittee shall submit to the MDEQ Environmental Permits Division a completed Form 2P application containing results of data collected from the facility's process wastewater discharge. The sampling data shall be representative of normal power generation activities. Based upon the results of the sampling, the permit may be reopened to address additional limits or requirements as deemed necessary to protect the POTW or water quality. The permittee shall submit the application within six months (180 days) of commencing discharge of effluent. [11 Miss. Admin. Code Pt. 6, R. 1.1.4.A(4)]