PERMIT RATIONALE FOR REISSUANCE
Robinwood Forest Utility Inc, Robinwood Development
Harrison County
Wortham, Mississippi
Water NPDES No. MS0050725
May 2022

I.	CLASSIFICATION – NPDES Commercial

II.	DESCRIPTION OF WASTEWATER – Domestic

III.	DESCRIPTION OF WASTEWATER TREATMENT – Domestic wastewater is collected and treated via an aerated lagoon followed by chlorine disinfection prior to discharge. Only one discharge to surface waters is described within the application with no increase in treated effluent flow proposed. 

IV.	RECEIVING WATERS – Unnamed Tributary of the Little Biloxi River. The receiving waters are located in the Coastal Streams drainage basin and are classified as Fish and Wildlife. At the point of discharge, the receiving stream does not appear on the current State of Mississippi 303(d) List of Impaired Waterbodies. The discharge does appear on a completed Total Maximum Daily Load (TMDL) for Fecal Coliform in the Biloxi River, Little Biloxi River, and Saucier Creek (December 1999). The facility utilizes chlorine disinfection, which complies with the conditions of the TMDL.

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Commercial Facility Guidelines (Technology), State of Mississippi Water Quality Criteria (MSWQS), Wasteload Allocation (WLA), TMDL

VI.	SUMMARY OF DISCHARGE LIMITATIONS – 

Parameter		Value				Basis
Flow			0.1 MGD		Design
BOD			30 mg/l 			Technology
Ammonia Nitrogen
-	Phase I		Report mg/l		WLA
-	Phase II	1.37 mg/l		WLA
Dissolved Oxygen
-	Phase I		Report mg/l		WLA
-	Phase II	≥6.0 mg/l		WLA
TSS 			60 mg/l 			Technology
E. coli			126 Col./100mL 	MSWQS
pH			6.0 to 9.0 S.U.	MSWQS
Chlorine		0.1 to 1.0 mg/l	Technology
Total Nitrogen		Report lbs/day	WLA
Total Phosphorus	Report lbs/day	WLA

VII.	CHANGES FROM PREVIOUS PERMIT – 

1.	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. 

2.	Ammonia Nitrogen limits of 1.37 mg/l have been added to the draft permit based on the State of Mississippi Water Quality Standards for Ammonia toxicity. The limit will be phased in on a 3-year schedule. 

3.	Minimum Dissolved Oxygen limits of 6.0 mg/l have been added to the draft permit as recommended in the Wasteload Allocation developed for the discharge. The limit will be phased in on a 3-year schedule. 

4.	Monitoring and reporting requirements for Total Nitrogen and Total Phosphorus have been added to the draft permit as recommended in the Wasteload Allocation developed for the discharge.