PERMIT RATIONALE FOR REISSUANCE
Verona POTW
Lee County
Verona, Mississippi
Water NPDES No. MS0042048
July 2017

I.	CLASSIFICATION – NPDES Municipal Major

II.	DESCRIPTION OF WASTEWATER – Domestic/Municipal Wastewater

III.	DESCRIPTION OF WASTEWATER TREATMENT – Domestic wastewater is collected and treated by a conventional lagoon with a hydrograph controlled discharge point.  No increase in permitted flow is proposed within the application.  See Attachment # 1 for flow schematic.

IV.	RECEIVING WATERS – Coonewah Creek.  The receiving stream is located within the Tombigbee River Basin and is classified as Fish and Wildlife.  See Attachment # 2 for the discharge location map.  At the point of discharge, the receiving stream appears on the current State of Mississippi 303(d) List for Evaluated or Impaired Waterbodies for Biological Impairment.  The discharge also appears on a completed Nutrient Total Maximum Daily Load (TMDL) for Town Creek (October 2009) and a completed Fecal Coliform TMDL for Town Creek (June 2002). Total Nitrogen and Total Phosphorus limits prescribed in the Nutrient TMDL and E. coli limits have been incorporated into the draft permit to comply with the conditions of the TMDLs. No effluent discharge from Verona POTW is allowed until instream monitoring stations indicate a stream flow of 10.0 cubic feet per second (cfs) or greater. The instream wastewater concentrations (IWCs) were calculated as shown below:

	IWC = {(Qw)/(Qw + Qr)
	Where:
	Qw = Design flow of the wastewater treatment facility
	Qr = Receiving stream flow

	Maximum permitted discharge flow rates at corresponding minimum stream flow rates
				
				1.05 MGD @ 10 cfs < stream flow < 26 cfs
				5.25 MGD @ 26 cfs < stream flow

Calculation for Stream flow ≥ 10.0 cfs:

		Where:
		Qw = 1.05 MGD (1.63 cfs)
		Qr = 10.0 cfs

IWC = {(1.63 cfs)/(1.63 cfs + 10.0 cfs)}*100 = 14.0 %

Calculation for Stream Flow ≥ 26.0 cfs:

		Where:
		Qw = 5.25 MGD (8.13 cfs)
		Qr = 26.0 cfs

IWC = {(8.13 cfs)/(8.13 cfs + 26.0 cfs)}*100 = 23.8 %
For maximum protection of the receiving water, the highest ratio of mixing, IWC = 23.8%, will be used in all calculations of chemical specific data results. 

V.	APPLICABLE GUIDELINES – 11 Mississippi Admin Code pt. 6, Municipal Facility Guidelines (Technology), Wasteload Allocation (WLA, Attachment # 3)

VI.	SUMMARY OF LIMITATIONS –

	Outfall 001

	Monthly Submittal
Parameter	Limit	Basis	
Flow	Report	Design	
BOD	30 mg/l	WLA	
BOD (Percent Removal)	65 % min	Technology	
pH	6.0 – 9.0	Admin Code	
TSS	90 mg/l	Technology	
TSS (Percent Removal)	65 % min	Technology	
Nitrogen (effluent)	Report	TMDL	
Phosphorus (effluent)	Report	TMDL	
E. coli	126 Col/100 ml	TMDL	
Ammonia Nitrogen (Phase I)	Report mg/L	WLA	
Ammonia Nitrogen (Phase II)	10 mg/L	WLA	
Dissolved Oxygen (Phase I)	Report mg/L	WLA	
Dissolved Oxygen (Phase II)	6.0 mg/L	WLA	

	Yearly Submittal (total)
Parameter	Limit	Basis	
Flow	1.05 MGD	Design	
BOD	263 lbs/day	WLA	
TSS	789 lbs/day	Technology	
Nitrogen (effluent, Phase I)	Report 	TMDL	
Nitrogen (effluent, Phase II)	100.77 lbs/day	TMDL	
Phosphorus (effluent, Phase I)	Report 	TMDL	
Phosphorus (effluent, Phase II)	45.67 lbs/day	TMDL	
Nitrogen (influent)	Report (quarterly)	TMDL	
Phosphorus (influent)	Report (quarterly)	TMDL	
Ammonia Nitrogen (Phase I)	Report	WLA	
Ammonia Nitrogen (Phase II)	88 lbs/day	WLA	

BIOASSAY AND CHEMICAL SPECIFIC EVALUATION

BIOASSAY

In accordance to State Regulation 11 Mississippi Admin Code, pt. 6, VI.B.2b., Verona POTW is required to perform Whole Effluent Toxicity (WET) tests as part of the renewal application.  The applicant should test in accordance with Short – Term Methods for estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms.  Short-term chronic WET tests should be performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate).

As a condition of the draft permit, Verona POTW will be required to begin the WET testing monitoring within 10 days of the date of permit issuance and complete the required testing within one year following effective date of the permit.  Verona POTW has a water salinity of less than 1,000 mg/l, so freshwater testing organisms will be used.  Verona POTW should use a dilution ratio of 23.8% when performing the Whole Effluent Toxicity testing.  Regulations require that those facilities with an IWC of than or equal to 1% performs a chronic whole effluent toxicity evaluation.  This test should be performed in accordance with Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms (EPA/600/4-91/002) or most recent addition.  The chronic WET tests should be performed on Ceriodaphnia dubia (invertebrate) and Pimephales promelas (vertebrate).

CHEMICAL SPECIFIC ANALYSIS

Major municipalities shall determine the toxic characteristics of their wastewater by analyzing for the toxic pollutant listed in Table III of appendix D of 40 CFR 122.  Chemical specific analysis shall be for total recoverable metals.  Municipalities shall submit twelve influent and effluent samples collected.  Chemical specific limits shall be placed in a permittee’s permit if any of the parameters evaluated in the toxic screening procedure indicated that reasonable potential for violations of the appropriate criteria (acute, chronic, and human health).

As a condition of the draft permit, Verona POTW will be required to begin the chemical specific monitoring within 10 days of the date of permit issuance and complete the required testing within one year following the effective date of the permit.

Upon receipt of the above data, pending the results, the permit will be reopened to make any modifications needed.  

VII.	CHANGES FROM PREVIOUS PERMIT

1.	The proposed draft permit contains Phase I and Phase II Total Phosphorus requirements for Outfall 001. The Phase I requirements are Total Phosphorus monitoring and reporting. The Phase II requirements reflect the limitations proposed in the Wasteload Allocation for the discharge dated June 26, 2017.

2.	The proposed draft permit contains Phase I and Phase II Total Nitrogen effluent requirements for Outfall 001. The Phase I requirements are Total Nitrogen monitoring and reporting. The Phase II requirements reflect the limitations proposed in the Wasteload Allocation for the discharge dated June 26, 2017.

3.	The proposed draft permit contains Phase I and Phase II Ammonia-Nitrogen effluent requirements for Outfall 001.  The Phase I requirements are Ammonia-Nitrogen monitoring and reporting. The Phase II requirements reflect the limitations proposed in the Wasteload Allocation for the discharge dated June 26, 2017.

4.	The proposed draft permit contains Phase I and Phase II Dissolved Oxygen effluent requirements for Outfall 001. The Phase I requirements are Dissolved Oxygen monitoring and reporting. The Phase II requirements reflect the limitations proposed in the Wasteload Allocation for the discharge dated June 26, 2017.

5.	The proposed draft permit contains E. coli limits of 126 Col./100 ml, which have replaced Fecal Coliform limits of 200 Col./100 ml as the bacterial standard for all freshwaters in MS designated as Recreation, Fish and Wildlife Support, and/or Public Water supply.

6.	The proposed draft permit contains Total Suspended Solids (TSS) percent removal limits of 65%, in accordance with 40 CFR 133.105.

7.	The proposed draft permit contains updated dilution ratios for the allowable discharge conditions to protect against ammonia toxicity in the receiving stream. 

Upon issuance of this permit, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase I; Phase II limitations shall not apply at this time.

Beginning upon completion and start-up of wastewater treatment units designed to meet the Phase II parameters denoted in this permit or five (5) years after the issuance of the permit, whichever comes first, the permittee shall achieve compliance with the effluent limitations specified for the parameters noted as Phase II; Phase I limitations shall no longer be in effect at this time. The permittee shall notify our office orally at least 48 hours prior to start-up of the wastewater treatment units designed to meet the Phase II parameters and in writing no later than 5 days after start-up.

The permittee shall submit an engineering report that describes how the facility will come into compliance with the Phase II limitations.

ATTACHMENTS

Attachment # 1 – Flow Diagram 
Attachment # 2 – Discharge Location Topography Map 
Attachment # 3 – Wasteload Allocation

Attachment #1 – Flow Diagram
Attachment #2 – Discharge Location Topography Map

Attachment #3 – Wasteload Allocation