PERMIT RATIONALE FOR REISSUANCE
Hickory Flat POTW
Benton County
Hickory Flat,, Mississippi
Water NPDES No. MS0024694
October 14, 2025

I.	CLASSIFICATION – Municipal NPDES Minor

II.	DESCRIPTION OF WASTEWATER – Domestic Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Domestic wastewater is collected and treated conventional lagoon followed by chlorine disinfection.  No increase in treatment capacity is proposed within the application.  

IV.	RECEIVING WATERS – Oaklimiter Creek.  The receiving stream is located within Yazoo River Basin and is classified as Fish and Wildlife.  At the point of discharge the receiving stream does not appear on the most recent State of Mississippi 303(d) list of evaluated or impaired waterbodies. The permit contains Nitrogen and Phosphorus reporting to comply with the Nutrient TMDL for the Little Tallahatchie River. The 7Q10 for the receiving stream is 0.61 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, 0.09 MGD or 0.1395 cfs
	QR = Receiving stream 7Q10, 0.61 cfs

IWC = {(0.1395 cfs)/(0.1395 cfs + 0.61 cfs)}*100 = 18.6 %

V.	APPLICABLE GUIDELINES – 11 MS Admin Code pt. 6 (MSWQS), 2025 Wasteload Allocation (WLA), Municipal Guidelines (Technology), Total Maximum Daily Load (TMDL)

VI.	SUMMARY OF LIMITATIONS –
Parameter	Value				Basis
Flow						0.09 MGD			Design
BOD5						30 mg/l (Monthly Avg.)		WLA
TSS						90 mg/l (Monthly Avg.)		Technology
Ammonia Nitrogen 	Phase I		10 mg/l			WLA
Ammonia Nitrogen	Phase II		6 mg/l			WLA
Dissolved Oxygen 				6.0 mg/l			MSWQS
E. Coli		 				126 Col./100 ml			MSWQS
Chlorine, Total Residual		0.059 mg/l 			*See Calculation
pH						6.0 – 9.0 SU			MSWQS
Total Nitrogen					Report			TMDL
Total Phosphorus				Report 			TMDL

Total Residual Chlorine Calculations

Limitation Calculation = (Numeric Criteria)/(IWC)

IWC = 18.6 %
Chlorine Acute Limitation Calculation

Chlorine Acute Freshwater Stream Standard = 0.019 mg/l

(0.019 mg/l)/(0.186) = 0.102 mg/l

Chlorine Chronic Limitations Calculation

Chlorine Chronic Freshwater Stream Standard = 0.011 mg/l

(0.011 mg/l)/(0.186) =0.059 mg/l

VII.	CHANGES FROM PREVIOUS PERMIT

The permit requires a reduction in ammonia nitrogen limitations to comply with the current ammonia toxicity standard. The reduction will be phased into the permit. The facility will be required to comply with phase 1 limitations upon issuance and must be in compliance with phase 2 limitations no later than 3 years after permit issuance. The facility is required to submit an engineering report 1 year after issuance. The report must detail how the facility will come into compliance with the reduced limitations.