PERMIT RATIONALE FOR REISSUANCE
Chunky POTW
Newton County
Chunky, Mississippi
Water NPDES No. MS0024767
May 2023

I.	CLASSIFICATION –Municipal NPDES Minor 

II.	DESCRIPTION OF WASTEWATER – Domestic/ Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Municipal wastewater is collected and treated by means of a conventional lagoon followed by disinfection.  No increase in flow is proposed within the application.  

IV.	RECEIVING WATERS – Wetlands thence Chunky River.  The receiving water is located within the Pascagoula River Basin, and is classified as Recreational.  Chunky River does not appear on the appear on the Updated 303(d) list impaired waterbodies. The discharge appears in a Completed TMDL for Pathogens. The facility utilizes chlorine disinfection, which complies with conditions of the TMDL. At the point of discharge the 7Q10 for the receiving stream is 5.2 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, 0.03 MGD or 0.047 cfs
		 Qr = Receiving stream 7Q10, 5.2 cfs.

IWC = {(0.047 cfs)/(0.047 cfs + 5.2 cfs)}*100 = 0.89 %

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

VI.	SUMMARY OF LIMITATIONS –
Parameter			Flow				Basis
Flow				0.03 MGD			Design
BOD5( Phase I)		45 mg/l 			WLA
BOD5( Phase II)		2 mg/l 				WLA
BOD (Percent Removal)	65% Minimum		Technology
NH3 -N (Phase I)		Report mg/l			WLA
NH3 -N (Phase II)		1 mg/L				WLA
Minimum DO			6 mg/l				Admin Code
TSS				90 mg/l 			Technology
E. coli				126 Col./100 ml		Admin Code
Chlorine, Total Residual	1.0 mg/l 			Admin Code & IWC
pH				6.0 – 9.0 SU			Admin Code

BOD5, DO limits are based on the Wasteload Allocation and modeled for oxygen depletion in the receiving stream. The toxicity limit for Cl2 was determined, and the facility will not be allowed to discharge over 1.0 mg/l maximum, which is less the toxicity limit. 

*Phase II limitations were based on a model that reflects an accurate discharge point, which was determined via field inspection to be a discharge into wetlands, not directly into the Chunky River. An alternative discharge location should be considered.

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.