PERMIT RATIONALE FOR REISSUANCE
Tunica County Utility District, Dundee Facility
Tunica County
Dundee, Mississippi
Water NPDES No. MS0058165
March 2019

I.	CLASSIFICATION – NPDES Minor Municipal

II.	DESCRIPTION OF WASTEWATER – Domestic Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Wastewater is collected and treated by means of an extended aeration activated sludge system followed by chlorine disinfection prior to discharge. Only one discharge to surface waters is described in the application with no increase in treated effluent flow proposed. 

IV.	RECEIVING WATERS – Unnamed Tributary of Cypress Lake. The receiving waters are located in the Yazoo River drainage 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 of Impaired Waterbodies, nor does the facility appear on a completed Total Maximum Daily Load (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, 0.05 MGD or 0.078 cfs
		 Qr = Receiving stream 7Q10, 0.0 cfs.

IWC = {(0.078 cfs)/(0.078 cfs + 0.0 cfs)}*100 = 100 %

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), Wasteload Allocation (WLA)

VI.	CHANGES FROM PREVIOUS PERMIT – 

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

Total Nitrogen and Total Phosphorus monitoring have been placed in the draft permit in accordance with the WLA developed for the discharge dated March 6, 2019. 

VII.	SUMMARY OF DISCHARGE LIMITATIONS – 
Parameter			Flow			Basis
Flow				0.05 MGD		Design
BOD5				10 mg/l 		WLA
BOD (Percent Removal)	85% Minimum	Technology
Minimum DO			6 mg/l			WLA
TSS				30 mg/l 		Technology
TSS (Percent Removal)	85% Minimum	Technology
NH3-N				2 mg/l 			WLA
E. coli				126 Col./100 ml	Admin Code
Chlorine, Total Residual	0.011 mg/l 		WLA
pH				6.0 – 9.0 SU		Admin Code
Total Nitrogen			Report lbs/day		WLA
Total Phosphorus		Report lbs/day		WLA

The minimum and maximum values for Dissolved Oxygen in the aeration basin, 30-Minute Sludge Settleability in the aeration basin, and influent pH must be reported.