PERMIT RATIONALE FOR REISSUANCE
Noxapater POTW, North
Winston County
Noxapater, Mississippi
Water NPDES No. MS0025241
March 2023

I.	CLASSIFICATION –Municipal NPDES Minor 

II.	DESCRIPTION OF WASTEWATER – Domestic / Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated by means of a lagoon, followed artificial wetlands.  No increase in flow is proposed within the application.  

IV.	RECEIVING WATERS – Unnamed Tributary of Tallahaga Creek.  The receiving water is located within the Pearl River Basin, and is classified as Fish and Wildlife.  Tallahaga Creek appears on the current State of Mississippi 303(d) list of impaired waterbodies, as impaired with monitoring data for aquatic life support due to biological impairment. The requirement for a Mercury Minimization Plan, as set forth in the mercury TMDL, has been completed in the previous permit. The discharge is also listed in a Completed TMDL due to Pathogens. The permit contains limitations that comply with the conditions of the TMDL. At the point of discharge the 7Q10 for the receiving stream is 0.0 cfs.  The instream wastewater concentration at the point of discharge can be determined by the following calculation:
IWC = {(Qw)/(Qw + Qr)}*100

	Where, Qw = Design flow of the wastewater treatment facility, 0.06 MGD or 0.093 cfs
		 Qr = Receiving stream 7Q10, 0.0 cfs.

IWC = {(0.093 cfs)/(0.093 cfs + 0.0 cfs)}*100 = 100 %

V.	APPLICABLE GUIDELINES – 11 MS Admin Code pt. 6, Municipal Facility Guidelines

VI.	SUMMARY OF LIMITATIONS –
Parameter				Flow				Basis
Flow					0.06 MGD			Design
BOD5					10 mg/l				WLA
BOD (Percent Removal)		85% Minimum			Admin Code	
Minimum DO				6 mg/l				WLA
TSS					30 mg/l				Admin Code	
TSS (Percent Removal)			85% Minimum			Admin Code	
NH3-N (Phase I)			2 mg/l				WLA
NH3-N (Phase II)			1.37 mg/l			WLA
E Coli (col/100ml)			200 Col./100 ml 		Admin Code	
Chlorine, Total Residual 		0.011 mg/l 			Admin Code & IWC
pH					6.0 – 9.0 SU			Admin Code	
Total Nitrogen				Report mg/l			WLA
Total Phosphorus			Report mg/l			WLA

VII.	CHANGES TO PREVIOUS PERMIT—

•	Ammonia Nitrogen limitation of 1.37 mg/l has been phased into the permit (Phase II)

•	Reporting Requirements for Nutrients (Total Nitrogen and Total Phosphorus) have been added to the draft permit

•	The permittee shall achieve compliance with the effluent limitations specified for discharge in accordance with the following schedule:

Upon issuance of this permit, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase I; Phase II parameters shall not apply at this time.  Beginning upon completion and start-up of improvements needed to comply with the Phase II parameters, or by three years after permit issuance, the facility shall comply with the parameters noted as Phase II ; Phase I parameters shall not apply at this time. The permittee shall notify our office orally at least 24 hours prior to start-up and in writing no later than 48 hours after start-up of the needed improvements.