PERMIT RATIONALE FOR REISSUANCE
Shaw POTW
Bolivar County
Shaw, Mississippi
Water NPDES No. MS0024953
October 9,2025

I.	CLASSIFICATION – NPDES Minor Municipal

II.	DESCRIPTION OF WASTEWATER – Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Municipal wastewater is collected and treated by means of a conventional lagoon. No increase in flow is proposed within the application.  

IV.	RECEIVING WATERS – Unnamed drainage ditch thence into Porter Bayou.  The receiving waters are located within the Yazoo River Basin. The unnamed drainage ditch is classified as ephemeral and Porter Bayou is classified Fish and Wildlife.  Neither waterbody appears on the 2018 State of Mississippi 303(d) List of Impaired Waterbodies.  This facility is listed in a completed Total Maximum Daily Load (TMDL) for Nutrients and Organic Enrichment / Low DO (June 2008). The draft permit contains limitations for Total Nitrogen and Total Phosphorous as prescribed in the TMDL. 

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 0.2 cfs. The Instream Wastewater Concentration (IWC) at the point of the discharge is determined by the following calculation:

IWC = {(Qw)/(Qw + QR)} * 100
            Where:
            Qw = Design flow of the wastewater treatment facility 0.36 MGD or 0.56 cfs.  
            QR = Receiving stream 7Q10, 0.09 cfs.

IWC = {(0.56 cfs)/(0.56 cfs + 0.2 cfs)} * 100 = 96.54%

V.	APPLICABLE GUIDELINES – 11 MS Admin Code Pt 6, Commercial/Municipal Facility Guidelines (Technology), MS Water Quality Standards, Wasteload Allocation (WLA), TMDL

VI.	CHANGES FROM PREVIOUS PERMIT – Ammonia Nitrogen Limitation was reduce to comply with the updated Ammonia Toxicity Standard. 

VII.	SUMMARY OF LIMITATIONS –

Parameter				Value				Basis
Ammonia Nitrogen, Total (Phase 1)	2.0 mg/L			WLA
Ammonia Nitrogen, Total (Phase 2)	1.4 mg/L			WLA
Chlorine, Total Residual		0.011 mg/L			WLA 
E. coli					126 (#Col/100mL)		MS WQS 
Flow					0.36 MGD			Design
Nitrogen, Total			34.5 lbs/day			WLA/TMDL
BOD5					30 mg/L			WLA/MS WQS
BOD5, Percent Removal		65%, Minimum		Technology
Oxygen, Dissolved			6.0 mg/L, Minimum		WLA
Phosphorous, Total			15.6 lbs/day			WLA/TMDL
TSS					90 mg/L			Technology
TSS, Percent Removal		65%, Minimum		Technology
pH					6.0 – 9.0 SU			MS WQS

The Permittee shall comply with phase 1 limitations upon issuance of the permit. The facility shall comply with phase 2 limitations upon completion of the upgrades required to comply the limitations, but no later than 3 years after issuance. 

The Permittee must submit an engineering report detailing how the facility will comply with phase 2 limitations. The report is due 1 year after issuance.