PERMIT RATIONALE FOR REISSUANCE OF NPDES PERMIT
Texas Eastern Transmission Corporation, Yazoo City Compressor Station
Yazoo County
Yazoo City, Mississippi
Water NPDES Number: MS0047457
May 11, 2013

I.	FACILITY INFORMATION
            Permitting Agency: 		Mississippi Department of Environmental Quality (MDEQ)
Facility Name:  	Texas Eastern Transmission Corp., Yazoo City Compressor Station
Facility Address:  	5170 Racetrack Road, Yazoo City, MS  39194  
	NPDES Permit No.: 	 MS0047457
SIC Code:  			 4922
Permit Writer:  		 Deanna Rush
II.	PROPOSED PERMITTING ACTION
Texas Eastern Transmission Corporation has applied to the MDEQ for re-issuance of a National Pollutant Discharge Elimination System (NPDES) permit to discharge treated wastewater into Willis Creek thence into the Yazoo River.  The NPDES permit issued to this facility expired May 31, 2011.  The MDEQ received a permit renewal application December 1, 2010. The permit has been administratively continued. 
III.	NATURE OF BUSINESS

The Yazoo City Compressor Station is natural gas compressor station that utilizes a natural gas-fired turbine to compress natural gas for continued transport through the interstate pipeline system.  This facility is an integral part of a natural gas transportation pipeline system that moves natural gas from the Gulf Coast to marketing areas in the Northeast.  

IV.	EFFLUENT AND RECEIVING STREAM FLOW DATA

The only discharge into Willis Creek is from a 12,500 gallon capacity holding tank (Outfall 001) which contains treated wastewater from the facility.  The wastewater entering the treatment system is collected from compressor building sumps, air receiver condensate, equipment cleaning, turbine pit cleaning, secondary containment contents, (when oil sheen is observed ) and groundwater from intermittent remedial activities.

V.	303(d) ISSUES
Willis Creek is not on the 2012 Section 303(d) List of Impaired Water Bodies. 
However, a TMDL has been developed for total nitrogen, total phosphorus and organic enrichment/low dissolved oxygen for Willis Creek. In addition, A TMDL has been developed for Legacy Pesticides targeting DDT and Toxaphene for the Yazoo River Basin.   DDT and Toxaphene are not used at the facility and the permit application was marked believed absent; therefore, the facility discharge is not expected to contribute to the impairment of the Yazoo River Basin for DDT and Toxaphene. 
          
VI.	TYPE OF WASTEWATER TREATMENT:

The first step in the wastewater treatment train is an equalization tank in which pH adjustment and/or flocculation is conducted, if deemed necessary.  This step is followed by oil/water separation, sediment filters, clay/coal filters, carbon filters, additional sediment filters and then storage in the 12,500 gallon holding tank.  The treated wastewater is discharged by opening a valve in the bottom of the tank.  It takes approximately seven hours to drain the tank.  The maximum discharge in one day is 12,500 gallons. 

VII.	EPA APPLICABLE CATEGORICAL GUIDELINES

There are no applicable categorical guidelines associated with this discharge.

VIII.	STATE APPLICABLE GUIDELINES
State of Mississippi Water Quality Criteria for Intrastate, Interstate, and Coastal Waters 	(Adopted by Mississippi Commission on Environmental Quality: August 23, 2007), 	hereafter referred to as WPC-2.

IX.	DATA FROM APPLICATION FORM (2C)

Table 1  Form 2C Data

Parameter	Maximum Daily Value 	
BOD5	<2 mg/l	
COD	<20 mg/l	
TOC	<1.0 mg/l	
TSS	<4.0 mg/l	
Ammonia (as N)	0.10 mg/l	
Flow	0.0125 MGD	
Temperature	78 degrees Fahrenheit	
pH	6.5-7.2 SU	
Oil & Grease	<5 mg/l	
PCB 1242	<0.5 µg/L	
PCB 1254	<0.5 µg/L	
PCB 1221	<0.5 µg/L	
PCB 1232	<0.5 µg/L	
PCB 1248	<0.5 µg/L	
PCB 1260	<0.5 µg/L	
PCB 1016	<0.5 µg/L	

X.	WATER QUALITY LIMITATIONS BASED ON WASTE-LOAD ALLOCATION (WLA)

Table 2 Waste Load Allocation Limitations
Parameter	Average	Maximum	
CBOD5	2 mg/l	4  mg/l	
NH3-N	2 mg/l 	4  mg/l 	
Minimum DO	6.0	None	
Total Suspended Solids	30	45	
Total Nitrogen	0.520 lb/day	None	
Total Phosphorus	0.230 lb/day	None	
pH	6-9	6-9	

XI.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

There are no categorical effluent guidelines for this type of facility; therefore, no categorical limitations are included in the permit. 

XII.	WATER QUALITY-BASED EFFLUENT LIMITS (WQBEL) - TOXICITY SCREENING

No pollutants were reported in the application which requires a toxicity screening; therefore it was not developed. 

XIII.	PROPOSED FINAL LIMITATIONS 

  Table 3: Average Permit Limitations

Outfall	Parameter	Present Average Limitation	Proposed Average Permit Limitation	Basis

001	Flow	Report	Report	Technical Judgment	
	Oil & Grease	10 mg/l	10 mg/l	Technical Judgment	
	TSS	30 mg/l	30 mg/l	WLA	
	CBOD5	Report Only	0.09 lb/day	WLA	

Outfall	Parameter	Present Permit Limitation
Maximum	Proposed Maximum Permit Limitation	Basis

001	Flow	Report	Report	Technical Judgment	
	Oil & Grease	15 mg/l	15 mg/l	Technical Judgment	
	TSS	45 mg/l	45 mg/l	WLA	
	CBOD5	Report Only	4  mg/l	WLA	
	PCB-1016	0.000045	0.000045	State WQ	
	PCB-1221	0.000045	0.000045	State WQ	
	PCB-1232	0.000045	0.000045	State WQ	
	PC B-1242	0.000045	0.000045	State WQ	
	PCB-1248	0.000045	0.000045	State WQ	
	PCB-1254	0.000045	0.000045	State WQ	
	PCB-1260	0.000045	0.000045	State WQ	

XIV.	BASIS FOR PERMIT LIMITATIONS	

The PH limit is based on the State of Mississippi Water Quality Criteria adopted August 23, 2007.  The limitation for PCBs are based on State of Mississippi Water Quality Standards adopted November 16, 1995.  The average limitations for carbonaceous oxygen demand (CBOD5 and total suspended solids (TSS) are based on a waste load allocation developed by the TMDL/WLA Branch of the MDEQ.   Oil & Grease limitations, established in a previous permitting action, are based technical judgment using a 1974 EPA memorandum: Oil & Grease Limitations for Petroleum Marketing terminals.  Flow will be measured with a totalizer once per week and for each discharge event.  Oil & Grease, CBOD5, TSS, pH, and the PCBs shall be measured by grab sample once per month. 
XV.	MONITORING 

The monitoring type for Oil & Grease, TSS, CBOD55 and pH will be a grab sample at a testing frequency of once/month.