PERMIT RATIONALE FOR REISSUANCE
North Carrollton POTW
Carroll County
North Carrollton, Mississippi
Water NPDES No. MS0024741
October 2018

I.	CLASSIFICATION – NPDES Minor Municipal

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater 

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and biologically treated by means of a conventional lagoon followed by chlorine disinfection then dechlorination prior to discharge. The current design capacity of the facility is 0.10 MGD. Only one discharge to surface waters is described in the application with no increase in treated effluent flow proposed.

IV.	RECEIVING WATERS – Big Sand Creek. The receiving waters are located within the Yazoo River Basin and are classified as Fish and Wildlife. At the point of discharge, the receiving waters do not appear on the current State of Mississippi 303(d) List for Impaired Waterbodies. The discharge does appear on a completed Total Maximum Daily Load (TMDL) for Organic Enrichment/Low DO and Nutrients in Big Sand Creek (June 2008). The proposed draft permit incorporates Total Nitrogen and Total Phosphorus limits developed in accordance with the TMDL. The discharge also appears on a completed TMDL for Pathogens in the Yazoo River (June 2003). The facility utilizes chlorine disinfection, which complies with the conditions of the TMDL. 

The 7-day, 10-year minimum flow (7Q10) of the receiving stream is 6.4 cfs. The Instream Wastewater Concentration (IWC) at the point of the discharge is determined by the following calculation:
IWC = {(Qw)/(Qw + Qr)}*100

Qw = Design flow of the wastewater treatment facility, 0.1 MGD or 0.15 cfs
Qr = Receiving stream 7Q10, 6.4 cfs.

IWC = {(0.15 cfs)/(0.15 cfs + 6.4 cfs)} * 100 = 2.29 %

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), Wasteload Allocation (WLA), Big Sand Creek TMDL (June 2008)

VI.	CHANGES FROM PREVIOUS PERMIT – 

1.	E. coli has replaced fecal coliform as the bacterial indicator for all freshwaters in MS designated as Recreation, Fish and Wildlife Support, and/or Public Water supply. 

2.	Total Nitrogen and Total Phosphorus limits have been modified in accordance with limits developed in the Big Sand Creek Nutrient TMDL.

3.	Phase I reporting and Phase II limits have been added for the Ammonia Nitrogen parameter based on the WLA for the discharge dated October 29, 2018.

VII.	SUMMARY OF DISCHARGE LIMITATIONS – 
Parameter				Value		Basis
Flow					0.10 MGD		Design
BOD5					45 mg/l 		Technology
TSS					90 mg/l		Technology
E. coli					126 col/100 ml		Admin Code
	Chlorine, Total Residual		0.466 mg/l 		WLA
	Dissolved Oxygen			6.0 (Minimum)		WLA
	pH					6.0 – 9.0 SU		Admin Code
	Ammonia Nitrogen (Phase I)		Report mg/l		WLA
			        (Phase II)		11.5 mg/l		WLA
	Total Nitrogen (Phase I)		Report lbs/day		TMDL
		             (Phase II)		9.59 lbs/day		TMDL
	Total Phosphorus (Phase I)		Report lbs/day		TMDL	
			     (Phase II)		4.34 lbs/day		TMDL	

Upon issuance of this permit, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase I; Phase II limitations shall not apply at this time.
Beginning upon completion and start-up of improvements needed to comply with Phase II limitations or five (5) years after the issuance of the permit, whichever comes first, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase II; Phase I limitations shall not apply at this time. The permittee shall notify our office orally at least 48 hours prior to start-up and in writing no later than 5 days after start-up.