DRAFT PERMIT RATIONALE FOR REISSUANCE
Metal Impact South LLC
Union County
New Albany, Mississippi
Water NPDES No. MS0052523
September 25, 2025

I.	FACILITY INFORMATION

Facility Name:		Metal Impact South LLC
Facility Address:	795 Sam T Barkley Drive 
	New Albany, MS  38652    
New Albany, 
Permit No.:		MS0052523
SIC:			3463
Permit Writer:		Rusty Parrish
EPD Branch:		Water II Branch

II.	NATURE OF BUSINESS

Metal Impact South is a diversified contract manufacturer of aluminum impact extrusions 
		and cold forged steel products. They provide products in a wide range of industries 	
with a heavy concentration in the aerospace, automotive, military/defense, consumer product market, as well as agricultural equipment and the building product segments.

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

Outfall 001 discharge consists of process wastewater from various manufacturing processes. The facility has an average flow is 0.0265 MGD based on application data and discharges into Jasper Creek (7Q10 = 0.24 cfs = 0.155 MGD).

IV.	303(d) and TOTAL MAXIMUM DAILY LOADS (TMDL) ISSUES

Jasper Creek does not appear on the 2024 Mississippi List of Impaired Water Bodies. The facility complies with the following applicable TMDLs:

•	Sediment – Yazoo River Basin – Jasper Creek HUC 080302010404 – May 2019
•	Fecal Coliform – Yazoo River – Carroll, Holmes, Leflore, & Warren Counties – June 2003 – ID: 903063013
•	Sediment – Yazoo River Basin – Hills Region –  October 2020
•	Organic Enrichment/ Low Dissolved Oxygen – Tallahatchie & Yazoo Rivers – Yazoo River Basin – April 2008
•	Sediment – Tallahatchie River – Yazoo River Basin – June 2003 – ID: 908063046
•	DDT & Toxaphene – Yazoo River Basin – May 2003 – ID: 903051601
•	Fecal Coliform – Little Tallahatchie River – Panola County – January 2003 – ID: 903011703
•	Sediment – Yazoo River Basin – Delta Region – April 2008 – ID: 908041702
•	Total Nitrogen & Total Phosphorus – Selected Large Rivers in the Delta – Yazoo River Basin – June 2008 – ID: 908063054
•	DDT & Toxaphene – Yazoo River Basin – November 2005 – ID: 905110401
•	Fecal Coliform – Little Tallahatchie River – Union & Marshall Counties – January 2003 – ID: 903011702
•	Sediment – Little Tallahatchie River & Designated Streams in HUC 08030201 – Yazoo River Basin – February 2022

V.	TYPE OF WASTEWATER TREATMENT

Treatment occurs in the following order: equalization tank and lime holding tank, emulsion breaking chamber, oil separation chamber, lime chamber, flash flock, flocculation drop chamber, clarifying chamber, pH adjust chamber, bio tower which includes two stage reaction chamber, DAF unit, wet well, then a final holding tank before discharging to Jasper Creek.

The flocculation sludge that accumulates in the flocculation drop chamber will go through the following treatment: sludge holding tank, filter press – filtered water goes back to the equalization tank, the sludge from the filter press continues the process with 25 yard storage special waste then to waste disposal.

Note: see Appendix D in 2025 NPDES application for water flow line drawing.

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

40 CFR Part 433 – Metal Finishing Point Source Category, Subpart A – New Source Performance Standards (NSPS), specifically 433.16.

VII.	DATA FROM APPLICATION FORM 2C

Parameter	Maximum Daily Value (mg/L)	Maximum Monthly Value (mg/L)	Long-Term Average Daily Value (mg/L)	No. of Analyses	
BOD5	NA	NA	NA	NA	
COD	NA	NA	NA	NA	
TOC	NA	NA	NA	NA	
TSS	102	39	11.2	49	
Ammonia (as N)	1.02	1.02	0.109	25	
Flow	132,029 gallons	1,405,742 gallons	27,803 gallons	1827	
Temperature (winter)	27.7	22.9	24.7	63	
Temperature (summer)	32.1	27.8	24.7	65	
pH (min.)	6.10	6.93	7.05	257	
pH (max.)	7.84	7.15	7.05	257	
Cadmium, Total	ND	ND	ND	25	
Chromium, Total	0.116	0.116	0.007	25	
Copper, Total	0.043	0.043	0.004	25	
Lead, Total	ND	ND	ND	25	
Nickel, Total	0.090	0.090	0.008	25	
Silver, Total	0.012	0.007	0.003	25	
Zinc, Total	1.23	1.23	0.068	25	
Cyanide, Total	0.011	0.007	0.003	25	
Oil & Grease	2.10	1.40	0.81	25	
Aluminum, Total	10.3	5.59	1.76	26	

VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

Parameter	Average	
CBOD5 (mg/L)	10	
Total Ammonia Nitrogen (mg/L)	2	
Minimum DO (mg/L)	6	
E. coli (col/100 ml)	126	
Cl2 (mg/L)	0.075	
TN (lbs/day)	Report	
TP (lbs/day)	Report	
pH	6.0 – 9.0	

IX.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

See Attachment A

X.	TOXICITY SCREENING

See Attachment B

XI.	PROPOSED FINAL LIMITATIONS 

Average Permit Limitations

Parameter	Categorical Limitation (mg/L)	Water Quality Limitation (mg/L)	Current Permit Limitation (mg/L)	Proposed Permit Limitation (mg/L)	Basis	
Aluminum (TR)	N/A	0.23862	0.59	0.23862	WQL	
Cadmium (T)	0.07	0.01580	0.006	0.006	CPL	
Chromium (T)	1.71	1.65238	1.71	1.65238	WQL	
Copper (T)	2.07	0.16438	0.173	0.16438	WQL	
Lead (T)	0.43	0.02511	0.117	0.02511	WQL	
Nickel (T)	2.38	0.56085	0.754	0.56085	WQL	
Silver (T)	0.24	N/A	0.036	0.036	CPL	
Zinc (T)	1.48	1.71633	1.48	1.48	CPL	
Cyanide (T)	0.65	0.00886	0.011	0.00886	WQL	
Dissolved Oxygen	N/A	6.0 (min)	6.0 (min)	6.0 (min)	CPL	
TSS	31	-----	31	31	CPL	
pH	6.0 – 9.0 S.U.	6.0 – 9.0 S.U.	6.0 – 9.0 S.U.	6.0 – 9.0 S.U.	CPL	
CBOD5	N/A	10	10	10	CPL	
NH3	N/A	2	2	2	CPL	
Cl2	N/A	0.03238	0.037	0.03238	WQL	
Oil and Grease	26	N/A	26	26	CPL	
IC25	N/A	29.86	23.6%	29.86%	WQL	
E. coli	N/A	126 # colonies/ 100 mL	126 # colonies/ 100 mL	126 # colonies/ 100 mL	CPL	
WQL = Water Quality Limitation; CPL = Current Permit Limitation

Maximum Permit Limitations

Parameter	Categorical Limitation (mg/L)	Water Quality Limitation (mg/L)	Current Permit Limitation (mg/L)	Proposed Permit Limitation (mg/L)	Basis	
Aluminum (TR)	N/A	0.42611	1.06	0.42611	WQL	
Cadmium (T)	0.11	0.05239	0.067	0.05239	WQL	
Chromium (T)	2.77	7.32611	2.77	2.77	CPL	
Copper (T)	3.38	0.23992	0.282	0.23992	WQL	
Lead (T)	0.69	1.56289	0.69	0.69	CPL	
Nickel (T)	3.98	3.60029	3.98	3.60029	WQL	
Silver (T)	0.43	0.05949	0.073	0.05949	WQL	
Zinc (T)	2.61	1.70240	2.57	1.70240	WQL	
Cyanide (T)	1.20	0.03750	0.046	0.03750	WQL	
Dissolved Oxygen	N/A	---	2.13	2.13	CPL	
TSS	60	---	60	60	CPL	
pH	6.0 – 9.0 S.U.	----	6.0 – 9.0 S.U.	6.0 – 9.0 S.U.	CPL	
CBOD5	N/A	---	15	15	CPL	
NH3	N/A	---	3	3	CPL	
Cl2	N/A		0.055	0.055	CPL	
Oil and Grease	52	N/A	52	52	CPL	
E. coli	N/A	410 # colonies/ 100 mL	410 # colonies/ 100 mL	410 # colonies/ 100 mL	CPL	
WQL = Water Quality Limitation; CPL = Current Permit Limitation

Flow shall be measured continuously with a recorder. pH, TSS, Temperature, and Dissolved oxygen shall be monitored once per week. pH and Dissolved Oxygen shall be monitored with grab samples of the effluent. Temperature shall be monitored instantaneously and TSS shall be monitored with a 24 hour composite sample. BOD5, Ammonia as Nitrogen, Oil and Grease, Aluminum, Cadmium, Chromium, Copper, Lead, Nickel, Silver, Zinc, Cyanide, E. coli and Total Residual Chlorine shall be monitored twice per month.  All metals shall be monitored with 24-hour composite samples of the effluent. All other pollutants shall be monitored with grab samples of the effluent

XI.	ADDITIONAL INFORMATION

	Water Quality Limits determined for metals are based on a Hardness of 400 mg/l as CaCO3 using Hardness equations from EPA National Recommended Water Quality Criteria, The Metals Translator: Guidance For Calculating A Total Recoverable Permit Limit From A Dissolved Criterion, and IWC of 29.86%. Metal Translator calculations are based on TSS data collected from April 2014 - March 2015. A Hardness Study conducted at Jasper Creek from December 2006-February 2007 determined the average hardness of the receiving stream to be 604 mg/L.  The equations found in the criteria are applicable for instream hardness ranges from 25 mg/l to 400mg/l. If instream hardness is less than 25 mg/l, then a hardness value of 25 mg/l should be used to calculate the criteria. If instream hardness is greater than 400 mg/l, then a hardness of 400 mg/l should be used to calculate the criteria.

Total Toxic Organics shall be monitored twice per year with a grab sample of the effluent.  The term “TTO” shall mean total toxic organics, which is the summation of all quantifiable values greater than .01 milligrams per liter for the toxic organics identified in 40 CFR Part 433.11(e).

As is required in the existing permit, Metal Impact shall be required to perform chronic bioassays and comply with an IC25 limit, the IWC of their effluent, as required by the “State of Mississippi Wastewater Regulations”.  In the existing permit for the facility, the IWC of their effluent and thus the IC25 limit was established as 23.6%. As can be seen in Attachment B, the IWC of their effluent is now 29.86%. As result, the IC25 limit is now being established at 29.86%.

Effect on Static Renewal of Ceriodaphnia (%, 7-day Chronic), Effect on Static Renewal of
Pimephales (%, 7-day Chronic), Total Toxic Organics (TTO), Total Nitrogen, and Total Phosphorus analyses shall be submitted semi-annually and analyses for all other parameters shall be submitted monthly.

ATTACHMENT A
CATEGORICAL GUIDELINES

The following table is extracted from 40 CFR Part 433 – Metal Finishing Point Source 
Category; Subpart A - Metal Finishing Subcategory; 433.16 (NSPS)

Pollutant or pollutant property	Maximum for any 1 day	Monthly average shall not exceed	
	Milligrams per liter (mg/L)	
Cadmium (T)	0.11	0.07	
Chromium (T)	2.77	1.71	
Copper (T)	3.38	2.07	
Lead (T)	0.69	0.43	
Nickel (T)	3.98	2.38	
Silver (T)	0.43	0.24	
Zinc (T)	2.61	1.48	
Cyanide (T)	1.20	0.65	
TTO	2.13		
Oil and Grease	52	26	
TSS	60	31	
pH	6.0 – 9.0	

The term "Total Toxic Organics" is defined as the summation of all quantifiable values greater than 0.01 mg/L for the list of toxic organics found in 40 CFR 433.11(e).”  [40 CFR 433.11(e)]  

The permittee may, in lieu of monitoring, submit a toxic organic management plan for review and approval. Upon approval, the permittee may discontinue monitoring for TTO, but the following certification statement must be made in the comment section of every discharge monitoring report submitted: "Based on my inquiry of the person or persons directly responsible for managing compliance with the permit limitations (or pretreatment standard) for total toxic organics (TTO), I certify that, to the best of my knowledge and belief, no dumping of concentrated toxic organics into the wastewaters has occurred since filing of the last discharge monitoring report. I further certify that this facility is implementing the toxic organic management plan submitted to the permitting (or control) authority." [40 CFR 433.12(a)]

ATTACHMENT B

TOXICITY SCREENING AND WATER QUALITY LIMITATIONS CALCULATIONS

Water Quality Evaluation for discharge into Jasper Creek for Outfall 001

IWC	=	Instream Wastewater Concentration
Qw	=	maximum 30 day average wastewater flow, if available
Qr	=	receiving stream flow
Xw	=	historical effluent data
Xwa	=	permit limit from effluent guidelines
Xta	=	the calculated limit based on current effluent guidelines
Xt	=	the calculated instream concentration based on historical data from application
Xr	=	receiving stream concentration

IWC = 100 * (Qw / (Qr + Qw))

If Xr is zero or unknown then,

Based on a Hardness Study conducted at Jasper Creek from December 2006 - February 2007, the average hardness of the receiving stream was determined to be 604 mg/L.  Criteria for certain pollutants are hardness dependent. EPA’s National Recommended Water Criteria contains criteria adjustment equations for hardness dependent pollutants. The equations are applicable for instream hardness ranges from 25 mg/l to 400 mg/l. If instream hardness is less than 25 mg/l, then a hardness value of 25 mg/l should be used to calculate the criteria. If instream hardness is greater than 400 mg/l, then a hardness of 400 mg/l should be used to calculate the criteria.

Metal Translator Calculations

Kp = Kpo * TSS^α

Where:
Kp = Linear Partition Coefficient
Kpo = Regression Coefficient
TSS = Total Suspended Solids
α = Exponent Constant

Values are constants from EPA Document The Metals Translator: Guidance For Calculating A Total Recoverable Permit Limit From A Dissolved Criterion. The equations are also from this document.

The dissolved fraction is calculated as follows:

The 15th percentile of TSS is 5.0 mg/L from data taken from April 2014 – March 2015.

Water Quality Criteria recalculated from the hardness equations are as follows:

Parameter	Maximum (acute) (mg/L)	Average (chronic) (mg/L)	
Cadmium	0.007248	0.002185	
Chromium III	0.903488	0.203779	
Copper	0.054740	0.037507	
Lead	0.188525	0.003029	
Nickel	1.06903	0.16653	
Silver	0.0003036	N/A	
Zinc	0.331403	0.334114	

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.2358 multiplied by the WQC average and max:

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.2102 multiplied by the WQC average and max:

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.3889 multiplied by the WQC average and max:

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.2056 multiplied by the WQC average and max:

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.5061 multiplied by the WQC average and max:

The recalculated criteria would be as follows, the inverse of Cp/CT = 0.3318 multiplied by the WQC average and max:

Parameter	AWQC (mg/L)	Xt (mg/L)	Pass/Fail	
Cadmium (T)	0.03074	0.0029333	Pass	
Chromium (T)	4.29823	0.0041067	Pass	
Copper (T)	0.14076	0.0252667	Pass	
Lead (T)	0.91695	0.0029333	Pass	
Nickel (T)	2.11229	0.0528000	Pass	
Silver (T)	0.0349	0.0070400	Pass	
Zinc (T)	0.99880	0.7216000	Pass	
Cyanide (T)	0.022*	0.0064533	Pass	
Aluminum (T)	0.250	6.0426667	Fail	
*Value from State of Mississippi Water Quality Criteria August 23, 2007

Parameter	CWQC (mg/L)	Xt (mg/L)	Pass/Fail	
Cadmium (T)	0.00927	0.0029333	Pass	
Chromium (T)	0.96945	0.0041067	Pass	
Copper (T)	0.09644	0.0023467	Pass	
Lead (T)	0.01473	0.0029333	Pass	
Nickel (T)	0.32905	0.0046933	Pass	
Silver (T)	N/A	0.0046933	N/A	
Zinc (T)	1.00697	0.0398933	Pass	
Cyanide (T)	0.0052*	0.0017600	Pass	
Aluminum (T)	0.140	1.0325333	Fail	
*Value from State of Mississippi Water Quality Criteria August 23, 2007

Parameter	HHWQC* (mg/L)	Xt (mg/L)	Pass/Fail	
Cadmium (T)	0.168	0.0000529	Pass	
Chromium (T)	140.468	0.0000741	Pass	
Copper (T)	1.0	0.0000423	Pass	
Lead (T)	N/A	0.0000529	N/A	
Nickel (T)	4.584	0.0000847	Pass	
Silver (T)	N/A	0.0000318	N/A	
Zinc (T)	5.0	0.0007199	Pass	
Cyanide (T)	220.0	0.0000318	Pass	
Aluminum (T)	N/A	0.0186333	N/A	
*Value from State of Mississippi Water Quality Criteria August 23, 2007

Water Quality Limitations Calculations: