PERMIT RATIONALE FOR REISSUANCE
Bent Creek Utility Inc, Bent Creek Lagoon
Lamar County
Hattiesburg, Mississippi
Water NPDES No. MS0052868
May 2023

I.	CLASSIFICATION – Commercial NPDES 

II.	DESCRIPTION OF WASTEWATER – Domestic Wastewater 

III.	DESCRIPTION OF WASTEWATER TREATMENT – Domestic wastewater is collected and treated biologically by an aerated lagoon followed by constructed wetland.  

IV.	RECEIVING WATERS – Perkins Creek.  The receiving stream is located within the Pascagoula 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.  Pascagoula River has a TMDL for Pathogens, which the facility complies with via disinfection. Only one discharge to surface waters is described within the application.  
		At the point of discharge, the 7Q10 for the receiving stream is 0.32 cfs.  The 	instream wastewater concentration at the point of discharge can be determined using the 	following calculation:

IWC = {(Qw)/(Qw + QR)}*100

	Where:
	Qw = Design flow of the wastewater treatment facility, Phase I 0.174 MGD or 0.27 cfs, 	
	Phase II 0.595 MGD or 0.92 cfs. 
	QR = Receiving Stream 7Q10, 0.32 cfs.

IWC = {(0.92 cfs)/(0.92 cfs + 0.32 cfs)}*100 = 74 %

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

VI.	SUMMARY OF LIMITATIONS – 
	Parameter					Value		Basis
	Flow						0.595 MGD		Design
	BOD5						20 mg/l		Modeled
	TSS						60 mg/l 		Technology
	Ammonia Nitrogen				3.0 mg/l		MSWQS
	Dissolved Oxygen				> 6.0 mg/l 		MSWQS
	E. Coli						126 Col./100 ml		MSWQS
	Nitrogen, Total 					Report lbs/day		MSWQS
	Phosphorus, Total				Report lbs/day		MSWQS
	Chlorine, Total Residual			0.015 mg/l 		See Calculations
	pH						6.0 – 9.0 SU		MSWQS