PERMIT RATIONALE FOR REISSUANCE
Entergy Mississippi Inc, Grand Gulf Nuclear Station
Claiborne County
Port Gibson, Mississippi
Water NPDES No. MS0029521
May 15, 2019

I.	FACILITY INFORMATION

Facility Name:  Entergy Mississippi Inc, Grand Gulf Nuclear Station
Facility Address:  7003 Bald Hill Road 
Port Gibson, MS  39150    
Port Gibson, 
Permit No.:  MS0029521
SIC:  4911
Permit Writer:  Thomas Kelly
EPD Branch:  Water I 

II.	NATURE OF BUSINESS

Nuclear Powered Steam Electric Plant. The facility operations fall within SIC Code 4911-Steam Electric Power Generation.  This facility is classified as a NPDES major source.

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

External Outfalls

001 – 	Discharge from the Mixing/Discharge Basin. Effluent from this outfall is a combination of internal outfalls(s) 002, 004, 005, 006 and 011. This outfall has a maximum 30-day flow of 45.66 MGD and discharges to the Mississippi River.  

The Mississippi River is classified as “Fish and Wildlife” and has a 7Q10 flow of 82,082 MGD. 

013 – 	Discharge from Sediment Basin A - Effluent from this outfall consists of the combined discharge from the Bechtel shop, vehicle maintenance shop, ice house condensate, standby service water leakage, construction and site runoff, once through cooling, site processing facility HVAC, Internal Outfall 010 (Sanitary), and Internal Outfall 016 (Energy Service System). This outfall has a maximum daily flow of 2.9 MGD. 

014 -    Discharge from Sedimentation Basin B - This discharge is a combination of discharges from Outfall 007, standby service water leakage and releases, intermittent circulation water basin overflows, and storm water runoff.  This outfall has a maximum daily flow of 1.0 MGD. 

Outfalls 013 and 014 discharge to an unnamed creek thence to Hamilton Lake. The receiving stream is classified as “Fish and Wildlife” and has a 7Q10 flow of 0 MGD.  

Internal Outfalls

002 -	(Categorical: Cooling Tower Blowdown) – Natural draft and auxiliary cooling tower blowdown. This outfall has a maximum 30-day flow of 46.21 MGD and discharges via Outfall 001.

004 -	(Categorical: Cooling Tower Blowdown) – Unit A standby service water (SSW- A). This outfall has a maximum daily flow of 0.452 MGD and discharges via Outfall 001. 

005 -	(Categorical: Cooling Tower Blowdown) – Unit B standby service water (SSW-B). This outfall has a maximum daily flow of 0.529 MGD and discharges via Outfall 001.

006 -	(Categorical: Low Volume) – Low volume waste basin including demineralizer wastewater, carbon filter backwash, and water treatment building sump. This outfall has a maximum daily flow of 0.529 MGD and discharges via Outfall 001.

007 -	(Categorical:  Low Volume) – Miscellaneous wastewaters discharged into Sedimentation Basin B comprised of administrative building drains; yard and storm Drains; fire water pump house, oily waste sumps, ionics reject water, turbine building cooling water Blowdown, HVAC blowdown, air conditioner once-through cooling, outage air compressor once-through cooling, intermittent standby service water, plant service water leakage and small releases. This outfall has a maximum 30-day flow of 0.504 MGD and discharges via Outfall 014.

010 -	(Non-categorical) – Sanitary wastewater. This outfall has an average flow of 0.035 MGD and discharges via Outfall 013.

	011 - 	(Non-categorical) – Treated liquid rad wastewater. This outfall has a maximum 30-day flow of 0.0567 MGD.

016 - 	(Non-categorical) – Miscellaneous wastewaters from the energy services center inclusive of water softener backwash, air conditioning cooling tower blowdown and storm water runoff. This outfall has a maximum 30-day flow of 0.004 MGD and discharges via Outfall 013.

IV.	303(d) ISSUES

None.

V.	TYPE OF WASTEWATER TREATMENT:

Outfall 

001 -	Commingling of waste streams from Outfalls 002, 004, 005, 006, 011, and the cooling tower makeup bypass.
002 -	No treatment.
004 -	No treatment.
005 - 	No treatment.
006 - 	No treatment.
007 -	Oil/Water separation provided for selected internal waste streams.
010 -	Sanitary Wastewater Treatment Plant with treatment including activated sludge, aeration, chlorination and dechlorination. 
011 -	No treatment.
013 -	Oil/Water separation provided for selected internal waste streams.  Settling provided for commingled wastewaters.
014 -	Oil/Water separation provided for selected internal waste streams.  Settling provided for commingled wastewaters.
016 -	No treatment.

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

40 CFR Part 423 - Steam Electric Power Generation Point Source Category; Sections 423.12 (BPT-Best Practicable Control Technology Currently Available) and 423.13 (BAT-Best Available Technology Economically Available).

VII.	DATA FROM APPLICATION FORM (2C)

External Outfalls:

	Maximum Daily Value	
Parameter	Outfall 001	Outfall 013	Outfall 014	
BOD5	< 2  mg/L	< 2 mg/L	< 2  mg/L	
COD	31 mg/L	12 mg/L	21 mg/L	
TOC	13 mg/L	3.9 mg/L	6.9 mg/L	
TSS	6 mg/L	22 mg/L	27 mg/L	
Ammonia (as N)	< 0.1 mg/L	< 0.1 mg/L	0.14 mg/L	
Flow	24.16 MGD	2.9  MGD	0.07 MGD	
Temperature (Winter)	38.8 °C	Ambient	Ambient	
Temperature (Summer)	39.9 °C	Ambient	Ambient	
pH	8.65 SU	8.12 SU	8.4 SU	

	Maximum Daily Value	
Parameter	Outfall 001	Outfall 013	Outfall 014	
BOD5	< 2  mg/L	< 2 mg/L	< 2  mg/L	
COD	31 mg/L	12 mg/L	21 mg/L	
TOC	13 mg/L	3.9 mg/L	6.9 mg/L	
TSS	6 mg/L	22 mg/L	15 mg/L	
Ammonia (as N)	< 0.1 mg/L	< 0.1 mg/L	0.14 mg/L	
Flow	50.23 MGD	2.9  MGD	1.0 MGD	
Temperature (Winter)	46 °C	Ambient	Ambient	
Temperature (Summer)	39.6 °C	Ambient	Ambient	
pH	8.46 SU	8.12 SU	7.95 SU	
Bromide	< 0.2 mg/L	< 0.2 mg/L	--	
Chlorine, TR	-- 	--	--	
Fluoride	0.52 mg/L	--	--	
Nitrate-Nitrite	2.6 mg/L	--	--	
Nitrogen, Total Organic (as N)	2.6 mg/L	1.9 mg/L	--	
Phosphorus	1.4 mg/L	0.18 mg/L	0.13 mg/L	
Sulfate (as SO4)	390 mg/L	390 mg/L	7.9 mg/L	
Barium, Total	0.29 mg/L	0.16 mg/L	--	
Boron, Total	0.12 mg/L	< 0.1 mg/L	--	
Iron, Total1	2.9 mg/L	0.73 mg/L	0.6 mg/L	
Magnesium, Total	51 mg/L	32 mg/L	7.2 mg/L	
Manganese, Total	0.36 mg/L	0.24 mg/L	--	
Arsenic, Total1	0.0079 mg/L	0.0038 mg/L	0.002 mg/L	
Copper, Total	0.003 mg/L	0.0023 mg/L	 0.0019 mg/L	
Lead, Total	< 0.0005 mg/L	0.00054 mg/L	0.00083 mg/L	
Mercury, Total1	< 0.005 ug/l	< 0.003 ug/L	< 0.005 ug/l	
Nickel, Total	0.0077 mg/L	< 0.0059 mg/L	2.3 mg/L	
Zinc, Total1	0.46 mg/L	<0.026 mg/L	0.024 mg/L	
Cyanide, Total1	< 0.010 mg/L	< 0.010 mg/L	<0.010 mg/L	
Phenols, Total	< 0.005 mg/L	< 0.005 mg/L	0.01 mg/L	

	Internal Outfalls:

		Maximum Daily Value	
Parameter	Outfall 002	Outfall 0041	Outfall 0052	Outfall 0064	
BOD5	< 2 mg/L	< 1.0 mg/L	1.2 mg/L	1.5 mg/L	
COD	40 mg/L	55 mg/L	36 mg/L	< 20.0 mg/L	
TOC	13 mg/L	11.7 mg/L	12.2 mg/L	4.6 mg/L	
TSS	6.8 mg/L	5 mg/L	4 mg/L	16 mg/L	
Ammonia (as N)	< 0.10 mg/L	0.17 mg/L	0.23 mg/L	< 0.10 mg/L	

		Maximum Daily Value	
Parameter	Outfall 002	Outfall 0041	Outfall 0052	Outfall 006	
Flow	70.45 MGD	0.452 MGD	0.529 MGD	0.65 MGD	
Temperature (Winter)	Ambient	16.1 °C	18.8 °C	18.9 °C	
Temperature (Summer)	Ambient	26.2 °C	25.1  °C	24.5 °C	
pH	8.43 SU	7.51 SU	6.96 SU	8.51 SU	
Bromide	--	14.4 mg/L	12.1 mg/L	0.52 mg/L	
Chlorine, TR	--	<0.1 mg/L	<0.1 mg/L	<0.1 mg/L	
Fluoride	0.54 mg/L	0.32 mg/L	0.33 mg/L	0.35 mg/L	
Nitrate-Nitrite	2.7 mg/L	0.28 mg/L	0.63 mg/L	--	
Nitrogen, Total Organic	2.9 mg/L	1.27 mg/L	1.05 mg/L	0.40 mg/L	
Phosphorus	1.5 mg/L	2.86 mg/L	3.48 mg/L	3.38 mg/L	
Sulfate	530 mg/L	202 mg/L	257 mg/L	3370 mg/L	
Aluminum, Total	--	--	--	5.46 mg/L	
Barium, Total	0.34 mg/L	0.09 mg/L	0.09 mg/L	0.04 mg/L	
Boron, Total	0.14 mg/L	0.12 mg/L	0.11 mg/L	--	
Cobalt, Total	--	--	0.01 mg/L	--	
Iron, Total	3.0 mg/L	2.5 mg/L	3.16 mg/L	48.6 mg/L	
Magnesium, Total	61 mg/L	24.7 mg/L	25.9 mg/L	54.3 mg/L	
Manganese, Total	0.37 mg/L	0.08 mg/L	0.22 mg/L	1.47 mg/L	
Arsenic, Total	0.0085 mg/L	0.006 mg/L	--	0.012 mg/L	
Cadmium, Total	--	--	--	0.0008 mg/L	
Chromium, Total	--	--	--	0.125 mg/L	
Copper, Total 	--	0.039 mg/L	0.113 mg/L	0.098 mg/L	
Lead, Total	--	--	--	0.003 mg/L	
Mercury, Total	--	1.23e-5 mg/L	2.98e-5 mg/L	5.5e-6 mg/L	
Nickel, Total	0.0077 mg/L	0.16 mg/L	0.13 mg/L	0.136 mg/L	
Selenium, Total	--	--	--	0.007 mg/L	
Zinc, Total	0.982 mg/L	0.49 mg/L	0.62 mg/L	0.270 mg/L	
4-Nitrophenol	--	0.283 mg/L	--	--	
Benzidine	--	1.51 mg/L	--	--	
4-Bromophenyl Phenyl Ether	--	0.006 mg/L	--	--	

	Maximum Daily Value	
Parameter	Outfall 007	Outfall 0113	Outfall 016	Outfall 010	
BOD5	< 2 mg/L	< 2.0  mg/L	< 2  mg/L	22 mg/L	
COD	< 24 mg/L	< 4.32  mg/L	40  mg/L	--	
TOC	8.7 mg/L	< 0.33 mg/L	7.6 mg/L	--	
TSS	5 mg/L	1.4 mg/L	5.2 mg/L	22 mg/L	
Ammonia (as N)	<0.1 mg/L	0.042 mg/L	< 0.1  mg/L	32 mg/L	
Flow	0.504 MGD	0.1564 MGD	0.0143 MGD	0.415 MGD	
Temperature (Winter)	Ambient	31.2 °C	Ambient	Ambient	
Temperature (Summer)	Ambient	31.0 °C	Ambient	Ambient	
pH	8.5 SU	7.75 SU	8.19 SU	8.25 SU	
Fecal Coliform	--	--	--	138 col./100 ml	
Bromide	--	--	< 0.2 mg/L	--	
Chlorine, TR	0.1 mg/L	< 0.011 mg/L	0.12 mg/L	0.15 mg/L	
Fluoride	< 1.0 mg/L	--	0.16 mg/L	--	
Nitrate-Nitrite	< 0.5 mg/L	--	0.29 mg/L	--	
Nitrogen, Total Organic (as N)	2.1 mg/L	0.042 mg/L	< 1 mg/L	--	
Oil and Grease	1.5 mg/L		--	< 5 mg/L	
Phosphorus	0.16 mg/L	 0.74 mg/L	0.13 mg/L	--	
Alpha, Total	--	4.63 pCi/l	--	--	
Beta, Total	--	725 pCi/l	--	--	
Radium, Total	--	2.55 pCi/l	--	--	
Radium 228, Total	--	1.05 pCi/l	--	--	
Sulfate (as SO4)	6.2 mg/L	--	36 mg/L	--	
Barium, Total	0.034 mg/L	--	0.05 mg/L	--	
Cobalt, Total	--	0.111 mg/L	--	--	
Iron, Total	0.23 mg/L	 39.5 mg/L	--	--	
Magnesium, Total	7.7 mg/L	--	10 mg/L	--	
Molybdenum, Total	--	0.149 mg/L	--	--	
Manganese, Total	--	--	0.046 mg/L	--	
Arsenic, Total	--	--	0.0017 mg/L	--	
Chromium, Total	--	--	< 0.010 mg/L	--	
Copper, Total	--	 0.599 mg/L	--	--	
Mercury, Total	--	--	< 0.005 ug/L	--	
Thallium, Total	--	0.336 mg/L	--	--	
Zinc, Total	48 mg/L	--	< 0.020 mg/L	--	

All of the detectable concentrations provided on the application are listed above. The remaining pollutant data provided on the application for each outfall was reported as non-detectable (ND). 

1All pollutant values provided in this table for Outfall 004, except for TSS, Flow, and zinc, were estimated using the discharge data provided in the previous renewal application.  These pollutants were not sampled at the time the application was prepared.

2All pollutant values provided in this table for Outfalls 005, except for Flow and zinc, were estimated using the discharge data provided in the previous renewal application.  These pollutants were not sampled at the time the application was prepared.

3All pollutant values provided in this table for Outfall 011, except for TSS and Flow, were estimated using the discharge data provided in the previous renewal application.  These pollutants were not sampled at the time the application was prepared.

4Because this Outfall 006 has not discharged in several years, effluent could not be sampled. All pollutant values provided in this table were estimated using the discharge data provided in the previous renewal application.  

VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

	None. 

IX.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

Not Applicable.

X.	TOXICITY SCREENING

See Attachment A.

XI.	PROPOSED FINAL LIMITATIONS 

1.	Average Permit Limitations

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	Basis	
001	Flow (MGD)	--	--	Report 	Report	Continuously	Measurement	Monthly	Technical Judgment	
001	Temperature °F	--	--	Report	Report	Continuously	Continuous Recorder	Monthly	Technical Judgment	
001	Chlorine, FA	0.2 mg/L		0.2 mg/L	0.2 mg/L	See Permit	Check Requirements	Monthly	Categorical	
001	pH	--	6.0 SU	6.0 SU	6.0 SU	Weekly	Grab Sampling	Monthly	11 Miss. Admin Code Pt. 6. Ch. 2	
002	Flow (MGD)	--	--	Report 	Report	Twice per Month	Instantaneous Sampling	Monthly	Technical Judgment	
002	Chlorine, FA	0.2 mg/L	--	0.2 mg/L	0.2 mg/L	Continuously	Check Requirements	Monthly	Categorical	
002	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Twice per Month	24-hr Composite	Monthly	Categorical	
004	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Check Requirements	Monthly	Technical Judgment	
004	Chlorine, FA	0.2 mg/L	--	0.2 mg/L	0.2 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
004	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
005	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Instantaneous Sampling	Monthly	Technical Judgment	
005	Chlorine, FA	0.2 mg/L	--	0.2 mg/L	0.2 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
005	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
006	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Instantaneous Sampling	Monthly	Technical Judgment	
006	Oil and grease	15 mg/L	--	15 mg/L	15 mg/L	Once per Batch During Operation	Grab Sampling	Monthly	Categorical	
006	TSS	30 mg/L	--	30 mg/L	30 mg/L 	Once per Batch During Operation	Grab Sampling	Monthly	Categorical	
007	Flow (MGD)	--	--	Report 	Report	Twice per Month	Instantaneous	Monthly	Technical Judgment	
007	Oil and grease	15 mg/L	--	15 mg/L	15 mg/L	Twice per Month	Instantaneous	Monthly	Categorical	
007	TSS	30 mg/L	--	30 mg/L	30 mg/L 	Twice per Month	Grab Sampling	Monthly	Categorical	
007	Chlorine, TR	--	--	Report 	Report	Twice per Month 	Grab Sampling	Monthly	Technical Judgment	

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	Basis	
010	Flow (MGD)	--	--	Report 	Report	Continuously	Continuous Recorder	Monthly	Technical Judgment	
010	BOD (5-Day)	--	--	30 mg/L	30 mg/L	Twice per month	24-hour composite	Monthly	Domestic Guidelines	
010	TSS	--	--	30 mg/L	30 mg/L 	Twice per month	24-hour composite	Monthly	Domestic Guidelines	
010	Chlorine, TR	--	--	Report 	Report	Twice per month	Grab	Monthly	Technical Judgment	
010	E.Coli		126 per 100 ml	--	126 per 100 ml	Twice per month	Grab	Monthly	11 Miss. Admin Code Pt. 6. Ch. 2	
010	pH	--	6.0 SU	6.0 SU 	6.0 SU 	Twice per month	Grab	Monthly	11 Miss. Admin Code Pt. 6. Ch. 2	
011	Flow (MGD)	--	--	Report 	Report	Continuously	Pump Log	Monthly	Technical Judgment	
011	TSS	--	--	Report 	Report 	Monthly	Grab Sampling	Monthly	Technical Judgment	
013	Flow (MGD)	--	--	Report 	Report	Quarterly	Instantaneous Sampling	Annually	Technical Judgment	
013	TSS	--	--	Report 	Report 	Quarterly	Grab Sampling 	Annually	Technical Judgment	
013	pH	--	6.0 SU	6.0 SU 	6.0 SU 	Quarterly	Grab Sampling 	Annually	11 Miss. Admin Code Pt. 6. Ch. 2	
013	Zinc, TR	--	0.065  mg/L	--	Report	Monthly	24-hr Composite	Quarterly	Technical Judgment 	
014	Flow (MGD)	--	--	Report 	Report	Quarterly	Instantaneous Sampling	Annually	Technical Judgment	
014	TSS	--	--	Report 	Report 	Quarterly	Grab Sampling 	Annually	Technical Judgment	
014	Zinc, TR	--	--	--	Report	Monthly	24-hr Composite	Quarterly	Technical Judgment 	
014	pH	--	6.0 SU	6.0 SU 	6.0 SU 	Quarterly 	Grab Sampling	Annually	11 Miss. Admin Code Pt. 6. Ch. 2	
016	Flow (MGD)	--	--	Report 	Report	Twice per Quarter	Instantaneous Sampling	Annually	Technical Judgment	
016	Chlorine, TR	--	--	Report 	Report 	Twice per Quarter	Grab Sampling	Annually	Technical Judgment	
016	pH	--	6.0 SU	6.0 SU 	6.0 SU 	Twice per Quarter	Grab Sampling	Annually	11 Miss. Admin Code Pt. 6. Ch. 2	

2.	Maximum Permit Limitations

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	Basis	
001	Flow (MGD)	--	--	Report 	Report	Continuously	Measurement	Monthly	Technical Judgment	
001	Temperature °F	--	--	Report	Report	Continuously	Continuous Recorder	Monthly	Technical Judgment	
001	Chlorine, FA			0.5 mg/L	0.5 mg/L	See Permit	Check Requirements	Monthly	Categorical	
001	pH	--	9.0 SU	9.0 SU	9.0 SU	Weekly	Grab Sampling	Monthly	11 Miss. Admin Code Pt. 6. Ch. 2	
002	Flow (MGD)	--	--	Report 	Report	Twice per Month 	Instantaneous 	Monthly	Technical Judgment	
002	Chlorine, FA	0.5 mg/L	--	0.5 mg/L	0.5 mg/L	Continuously	Check Requirements	Monthly	Categorical	
002	Chlorination Duration	120 min	--	120 min	120 min	Twice per Month	Measurement	Monthly	Categorical	
002	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Twice per Month	24-hr Composite	Monthly	Categorical	
004	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Instantaneous 	Monthly	Technical Judgment	
004	Chlorine, FA	0.5 mg/L	--	0.5 mg/L	0.5 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
004	Chlorination Duration	120 min	--	120 min	120 min	Once per Batch During Operation	Measurement	Monthly	Categorical	
004	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
005	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Measurement	Monthly	Technical Judgment	
005	Chlorine, FA	0.5 mg/L	--	0.5 mg/L	0.5 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
005	Chlorination Duration	120 min	--	120 min	120 min	Once per Batch During Operation	Measurement	Monthly	Categorical	
005	Zinc, TR	1.0 mg/L	--	1.0 mg/L	1.0 mg/L	Once per Batch During Operation	Check Requirements	Monthly	Categorical	
006	Flow (MGD)	--	--	Report 	Report	Once per Batch During Operation	Instantaneous 	Monthly	Technical Judgment	
006	Oil and grease	20 mg/L	--	20 mg/L	20 mg/L	Once per Batch During Operation	Grab 	Monthly	Categorical	
006	TSS	100 mg/L	--	100 mg/L	100 mg/L	Once per Batch During Operation	Grab	Monthly	Categorical	
007	Flow (MGD)	--	--	Report 	Report	Twice per Month	Instantaneous	Monthly	Technical Judgment	
007	Oil and grease	20 mg/L	--	20 mg/L	20 mg/L	Twice per Month	Grab	Monthly	Categorical	
007	TSS	100 mg/L	--	100 mg/L	100 mg/L 	Twice per Month	Grab	Monthly	Categorical	

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Monitoring Frequency	Sample Type	DMR Reporting Frequency	Basis	
007	Chlorine, TR	--	--	Report	Report	Twice per Month	Grab	Monthly	Technical Judgment	
010	Flow (MGD)	--	--	Report 	Report	Continuously	Continuous Recorder 	Monthly	Technical Judgment	
010	BOD (5-Day)	--	--	45 mg/L	45 mg/L	Twice per Month	24-hr Composite	Monthly	Domestic Guidelines	
010	TSS	--	--	45 mg/L	45 mg/L	Twice per Month	24-hr Composite	Monthly	Domestic Guidelines	
010	Chlorine, TR	--	--	0.5 mg/L	0.5 mg/L	Twice per Month	Grab	Monthly	Technical Judgment	
010	E.Coli		410 col./100 ml	--	410 col./100 ml	Twice per Month	Grab	Monthly	11 MISS. ADMIN CODE PT. 6. CH. 2	
010	pH	--	9.0 SU	9.0 SU	9.0 SU	Twice per Month	Grab	Monthly	11 MISS. ADMIN CODE PT. 6. CH. 2	
011	Flow (MGD)	--	--	Report 	Report	Continuously	Pump Log	Monthly	Technical Judgment	
011	TSS	--	--	30 mg/L	30 mg/L	Monthly	Grab	Monthly	Technical Judgment	
013	Flow (MGD)	--	--	Report 	Report	Quarterly	Instantaneous	Annually	Technical Judgment	
013	TSS	--	--	Report 	Report 	Quarterly	Grab	Annually	Technical Judgment	
013	pH	--	9.0 SU	9.0 SU	9.0 SU	Quarterly	Grab	Annually	11 MISS. ADMIN CODE PT. 6. CH. 2	
013	Zinc, TR	--	0.065  mg/L	--	0.065  mg/L	Quarterly	Grab	Annually	11 MISS. ADMIN CODE PT. 6. CH. 2 	
014	Flow (MGD)	--	--	Report 	Report	Quarterly	Instantaneous	Annually	Technical Judgment	
014	TSS	--	--	Report 	Report 	Quarterly	Grab	Annually	Technical Judgment	
014	Zinc, Total Recoverable	--	0.065  mg/L	--	0.065 mg/L	Quarterly	24-hr Composite	Annually	11 MISS. ADMIN CODE PT. 6. CH. 2 	
014	pH	--	9.0 SU	9.0 SU	9.0 SU	Quarterly	Grab	Annually	11 MISS. ADMIN CODE PT. 6. CH. 2	
016	Flow (MGD)	--	--	Report 	Report	Twice per Quarter	Instantaneous	Annually	Technical Judgment	
016	Chlorine, TR	--	--	0.5 mg/L	0.5 mg/L	Twice per Quarter	Grab	Annually	Technical Judgment	
016	pH	--	9.0 SU	9.0 SU	9.0 SU	Twice per Quarter	Grab	Annually	11 MISS. ADMIN CODE PT. 6. CH. 2	

E. Coli

As part of the recent triennial review of Mississippi’s Water Quality Standards, revisions were made regarding the bacterial indicator for Mississippi’s freshwaters. The following information summarizes the revisions made regarding bacteria as part of the recently approved revisions to the WQS regulations:

1)	E.coli will now be the bacterial indicator used for all freshwaters in MS designated as Recreation, Fish and Wildlife Support, and/or Public Water Supply (replacing the use of fecal coliform).
2)	The specific language from the WQS regulations states that ‘Culturable E.coli should not exceed a geometric mean of 126 per 100 ml over a 30-day period, nor should the samples examined during a 30-day period exceed 410 per 100 ml more than 10% of the time.’

Accordingly, fecal coliform has been removed from the proposed permit and replaced with E. coli.  

126 Priority Pollutants Certification

The permittee shall certify, not less than once per year (with the DMR on January 28th of each year), that chemical products added for cooling tower maintenance, including such chemical used for corrosion inhibition, do not result in the discharge via cooling tower blowdown of any of the 126 priority pollutants (including but not limited to chromium and zinc) in detectable concentrations. Additionally, once for each product used for cooling system and/or boiler maintenance, compliance shall be demonstrated by submission of certification from the manufacturer that such product contains no priority pollutants

The addition of any chemical product to the cooling system and/or the boiler system other than those submitted with the application is prohibited unless prior written approval is obtained in accordance with condition S-10 on page 8 of this permit.  Chemicals used for the maintenance of cooling water chemistry and boiler water chemistry, or otherwise to operate or maintain these systems, shall not cause a violation of the terms and conditions contained in condition S-1 on page 5 of this permit.

Thermal Mixing Zone

The receiving water shall not exceed a maximum water temperature change of 2.8 degrees Celsius (5.0 degrees Fahrenheit) relative to the upriver temperature, outside a mixing zone not exceeding a maximum width of 60 feet from the river edge and a maximum length of 6,000 feet downstream from the point of discharge, as measured at a depth of 5 feet. The river edge shall be defined as being no further east than the mouth of the barge slip.  The maximum water temperature shall not exceed 32.2 degrees Celsius (90 degrees Fahrenheit) outside the same mixing zone, except then ambient temperatures approach or exceed this value.

Thermal Modeling

Thermal monitoring shall be performed any time the river stage is less than 0.5 feet (Vicksburg gauge) during winter months (November-April) or, is less than minus 1.2 feet (Vicksburg gauge) during the summer months (May-October). If these conditions occur and the plant is generating power, monitoring shall be performed upriver at PT.1 (surface/5 feet sub-surface), Discharge Outlet, Barge Slip Outlet, and down river at PT.7.  However, once monitoring has been performed at river stages less than those cited (0.5 feet during the winter months and minus 1.2 feet during the summer months), the river stages which existed at the time of thermal modeling, will then become the standard river stage during which a subsequent monitoring exercise must be performed if the river falls below that stage. Thorough documentation shall be maintained on file of the river stage during each period of thermal monitoring. This policy is subject to modification if any data collected during a particular stage indicates temperature variations not previously measured.

Report Submittal Requirement

Discharges from the following outfalls failed the toxicity screen because of a variability factor, i.e. only one sample was provided on the application. Based on technical judgment, the permittee will be required to monitor each outfall once per month when discharging, utilizing 24-hour composite sampling, until 12 effluent samples have been analyzed for each outfall.

•	Outfall 013 – Total Iron, Total Copper, Total Lead, and Total Nickel
•	Outfall 014 – Total Iron, Total Copper, Total Lead, and Total Nickel

If this data indicates a violation of water quality standards, the NPDES permit may be reopened and modified. Once all 12 samples have been collected for each pollutant, the permittee shall submit a report summarizing the results.

Application Submittal Requirements

On the first discharge following the effective re-issuance date of this permittee, the permittee shall collect one effluent sample from Outfalls 004, 005, 006, and 011 and test for the Part A and Part B pollutants listed on EPA Form 2C, Item V. For Part A pollutants, the application must contain the results of at least one analysis done for each pollutants listed in Part A.  For Part B pollutants, the application must contain analysis results of at least one analysis taken for each parameter in Part B that is believed present. This application should be submitted no later than the 28th day of the month following the completion of the effluent sampling.  The NPDES Permit may be modified if data indicates a violation of water quality standards for any of the above mentioned parameters.

XII.	BPJ STATEMENT: 

It is our Technical Judgement that the foregoing limitations represent 11 Miss. Admin. Code Pt.6, Ch. 1 and 2, and Technical Judgment.

ATTACHMENT A

CHEMICAL SPECIFIC SCREENING

Grand Gulf Nuclear Station has three external discharge points.  Outfall 001 is a combination of internal outfalls 002, 004, 005, 006 and 011 that discharges directly into the Mississippi River. Effluent from external Outfall 013 consists of the combined discharge from the Bechtel Shop, vehicle maintenance shop, Ice House Condensate, Standby Service Water Leakage, Construction and Site Runoff, Once-through cooling water, site processing facility HVAC, Internal Outfall 010 (Sanitary), Internal Outfall 016 (Energy Service System) which discharges to Hamilton Lake. Outfall 014 consists of a discharge from sedimentation Basin B, which includes water from the following: internal Outfall 007; standby service water leakage and releases; intermittent circulation water basin overflows; and storm water runoff. Outfalls 004, 005 and 006 are internal outfalls that discharge through Outfall 002 which discharge to Hamilton Lake.  

For Outfalls 001

Qr	= 7Q10 of receiving stream (Acute Screening) 
= 82,082 MGD
 
 	= Mean annual flow (Human Health Screening) 
= 653,272.60 MGD 

Qw	= Maximum 30 day value flow.
	= 45.66 MGD
	
IWC		= 100 * Qw /(Qr + Qw)
		= 100 * (45.66)/(82,082+45.66)  = 0.0556 %   (7Q10)
 		= 100 * (45.66)/(653272.7+45.66) = 0.007 % (Mean Annual)

Because IWC is less than 1 percent, an acute and human health toxicity screen will be performed. 

For Outfalls 013 

Qr	= Receiving Stream Flow 
	= 0 MGD (7Q10-Acute and Chronic Screening)
	= 5.8401 MGD (Mean Annual - Human Health Screening)

Qw	= Maximum 30 day value flow. 
	= 2.9 MGD (Outfall 013)

IWC(%)   = Qw /(Qr + Qw)*100
	  = 2.9/(5.881+2.9)*100 = 33 %  (Outfall 013) Mean
	  = 2.9/(0+2.9)*100 = 100 %  (Outfall 013) 7Q10=0 

Because IWC is greater than 1 percent, an acute, chronic and human health toxicity screen will be performed. 

For Outfalls 014 

Qr	= Receiving Stream Flow 
	= 0 MGD (7Q10-Acute and Chronic Screening)
	= 5.8401 MGD (Mean Annual - Human Health Screening)
	
Qw	= Maximum Daily flow was used because Maximum 30-day values were not available. 
	= 1.0 MGD (Outfall 014)
	
IWC(%)    = Qw /(Qr + Qw)*100
	 = 1.0/(5.8401+1.0)*100 = 14.62 %  (Outfall 014) Mean
	 = 1.0/(0+1.0)*100 = 100 %  (Outfall 014) 7Q10=0 

Because IWC is greater than 1 percent, an acute, chronic and human health toxicity screen will be performed. 

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