FINAL Engineering Site Visit Report for 

Tennessee Valley Authority’s 

 Widows Creek Fossil Plant 

Stevenson, AL

Prepared for:

U.S. Environmental Protection Agency

Engineering and Analysis Division

Office of Water 

1200 Pennsylvania Avenue 

Washington, DC 20004 

Prepared by:

Eastern Research Group, Inc. 

14555 Avion Parkway 

Suite 200 

Chantilly, VA 20151-1102 

July 18, 2007 

EPA Contract No. 68-C02-095 

Work Assignment 4-22 
i

TABLE OF CONTENTS 

Page 

1.0 SITE VISITED AND DATE .......................................................................................... 1 

2.0 ATTENDEES.............................................................................................................. 1 

3.0 BACKGROUND AND OBJECTIVES.............................................................................. 1 

4.0 PLANT DESCRIPTION................................................................................................ 2 

5.0 PLANT OPERATIONS................................................................................................. 3 

5.1 Coal Preparation.......................................................................................... 3 

5.2 Boiler Operation.......................................................................................... 4 

5.3 Selective Catalytic Reduction Operation.................................................... 4 

5.4 Particulate Control ...................................................................................... 6 

5.5 FGD System................................................................................................ 7 

5.6 Biofouling Control...................................................................................... 8 

5.7 Metal Cleaning Operation........................................................................... 8 

6.0 WASTEWATER MANAGEMENT ................................................................................. 9 

6.1 Intake Water................................................................................................ 9 

6.2 Coal Pile Runoff ....................................................................................... 11 

6.3 Low-Volume Waste.................................................................................. 11 

6.4 Metal Cleaning Waste............................................................................... 11 

6.5 Cooling Water........................................................................................... 12 

6.6 Ash Handling Water ................................................................................. 12 

6.7 FGD System Wastewater.......................................................................... 14 

7.0 REFERENCES .......................................................................................................... 15 

Appendix A LIST OF ATTENDEES 

Appendix B PICTURES FROM SITE VISIT 
ii

LIST OF TABLES 

Page 

A-1 List of Attendees................................................................................................. A-1 
iii

LIST OF FIGURES 

Page 

6-1 Wastewater Flow Diagram for Widows Creek......................................................10 

B-1 Coal Pile Runoff Pond at Widows Creek ............................................................B-1 

B-2 Ash Pond Dike at Widows Creek ........................................................................B-2 

B-3 Ash Pond at Widows Creek .................................................................................B-3 

B-4 Cenospheres Collected from the Ash Pond at Widows Creek.............................B-4 

B-5 Pumping Basin at Widows Creek ........................................................................B-5 

B-6 Constructed Wetland Cells for the Old Ash Pond Runoff at Widows Creek ......B-6 

B-7 Gypsum Pond at Widows Creek..........................................................................B-7 

B-8 Gypsum Pond Discharge to Widows Creek.........................................................B-8 
1

1.0 SITE VISITED AND DATE

Tennessee Valley Authority’s (TVA’s) Widows Creek Fossil Plant 

County Road 96 

Stevenson, AL 35772 

December 12, 2006 

2.0 ATTENDEES

 Appendix A lists the attendees. 

3.0 BACKGROUND AND OBJECTIVES

 Section 304(m) of the Clean Water Act (CWA) requires EPA to develop and 

publish a biennial plan that establishes a schedule for the annual review and revision of national 

effluent limitations guidelines and standards (ELGs) required by CWA section 304(b). During 

EPA’s 2005/2006 review of ELGs, EPA determined that the steam electric power generating 

point source category (40 CFR Part 423) is the second-largest discharger of toxic-weighted 

pollutants. EPA’s analyses indicated that the toxic-weighted loadings are predominantly driven 

by metals present in wastewater discharges, and that the wastestreams contributing the majority 

of the metals are associated with air pollution controls. Other potential sources of metals include 

coal pile runoff, metal/chemical cleaning wastes, coal washing, and certain low volume wastes. 

 In presenting the findings of the 2005/2006 study, EPA noted certain data 

limitations affect the Agency’s estimate of the potential hazard posed by discharges from this 

category and, therefore, EPA determined that further review of these discharges during the 

2007/2008 ELG planning cycle is warranted. Due to the limited resources and time available for 

conducting this study, EPA is concentrating its efforts for the 2007/2008 study on better 

characterizing pollutant sources and available pollution control technologies/practices for the 

pollutants responsible for the majority of the toxic-weighted pollutant loadings from steam 

electric facilities. This will focus the review on wastewater discharges from coal-fired power 

plants. 
2

 EPA intends to review overall plant operations and better understand the various 

wastewater sources present at steam electric plants. This review is expected to largely focus on 

ash handling wastes, wet flue gas desulfurization (FGD) wastes, coal pile runoff, and final 

effluent. 

 EPA and its contractor, Eastern Research Group, Inc. (ERG), conducted a site 

visit to TVA’s Widows Creek Fossil Plant (Widows Creek) on December 12, 2006. The purpose 

of the visit was to: 1) gather information about the plant’s operations, the wastewater discharges 

from the plant, and the wastewater management practices used to control the discharges; and 2) 

determine the feasibility of collecting and analyzing wastewater samples from steam electric 

power plants. 

4.0 PLANT DESCRIPTION

 TVA’s Widows Creek plant began operation in July 1952, when Unit 1 came on 

line. Units 2 through 6 were also completed in the early 1950’s. The plant added Units 7 and 8 

in the early 1960’s, with Unit 8 beginning operation in February 1965. At the time Unit 8 began 

operation, the Widows Creek plant was the largest power plant in the world. All eight of the 

generating units have coal-fired boilers, with a combined total capacity of 1,630 megawatts 

(MW); however, Units 7 and 8 account for approximately 55 percent of the capacity at the plant. 

On a yearly average, the plant generates approximately 65 percent of its available capacity. 

Widows Creek is located on approximately 1,300 acres of land in Stevenson, Alabama, beside 

the Guntersville Reservoir on the Tennessee River. 

 In 1970, Widows Creek retrofitted Unit 8 and in 1981 Unit 7 with FGD scrubbers 

to control the sulfur dioxide releases from the plant. In 2003/2004, the plant also retrofitted 

Units 7 and 8 with selective catalytic reduction (SCR) operations to control nitrogen oxide 

releases from the plant. The installation of these air pollution control devices not only reduces 

the sulfur dioxide and nitrogen oxide emissions, but it also reduces the mercury emissions from 

the plant. According to the EPRI representative, Widows Creek has some of the lowest mercury 

air emissions of any power plant in the country. 
3

 Units 1 through 6 at Widows Creek use a low-sulfur coal, which produces less 

sulfur dioxide emissions than a high-sulfur coal. In addition, Units 1 through 6 are also equipped 

with boiler optimization controls, which limit the production of nitrogen oxides. 

5.0 PLANT OPERATIONS

 Each of the eight generating units at Widows Creek has a coal-fired boiler. The 

plant uses approximately 15,000 tons of coal per day for the eight units. Each of the units 

generates wastewater; however, the quantity and characterization of the waste streams varies 

depending on the unit characteristics. 

 The Widows Creek site visit focused on the generating units and the wastewaters 

associated with these units. For a general description of the steam electric power generation 

process, see Section 3.2.1 of the Interim Detailed Study Report for the Steam Electric Power 

Generating Point Source Category. The remainder of this section describes the following seven 

operations at Widows Creek: 

y Coal preparation; 

y Boiler operation; 

y SCR operation; 

y Particulate control (includes wet fly ash handling); 

y FGD system operation; 

y Biofouling control; and 

y Metal cleaning operations. 

5.1 Coal Preparation

 The Widows Creek plant uses two different types of coal; a low-sulfur coal in 

Units 1 through 6 from the 20 Mile and Bowie mines in Colorado and a higher-sulfur coal in 

Units 7 and 8 from the Warrior, Pattiki, and Galatia mines in the Illinois Basin area. Because the 

plant uses two different types of coal, the plant manages two coal piles situated within the same 

area. Although there are two separate coal piles, all of the storm water runoff that contacts the 

coal is collected in a single pond. 
4

 For each unit, the plant transports the coal from the coal pile to individual unit 

bunkers by conveyor belts, which are covered. From the bunkers, the coal is sent to the 

pulverizers, where it is ground into a fine powder that is blown into the boiler using air. Some of 

the coal entering the pulverizers is too hard to be pulverized; these pyrites (rock-like coal pieces) 

are collected in a reject bin. The plant breaks the pyrites into smaller pieces, sluices them with a 

water stream, and transports it to the ash pond. 

5.2 Boiler Operation

 As the pulverized coal is blown into the boiler, it is combusted and gives off heat. 

The heat produced in the boiler is used to convert water into high-pressure steam. As the coal is 

combusted, solid, non-combustible constituents of the coal, referred to as ash, are generated. 

The heavy ash particles that collect on the bottom of the boiler are referred to as bottom ash. The 

finer particles that are light enough to be transferred out of the boiler with the flue gas exhaust 

are referred to as fly ash. At Widows Creek, a continuous stream of sluice water collects and 

removes the bottom ash and other slag from the bottom of the boiler. The fly ash is also sluiced 

from the particulate control devices, as described in Section 5.4. In addition, the plant 

periodically generates wastewater from washing the fire-side of the boiler. Wastewater 

associated with boiler cleaning is discussed in greater detail in Sections 5.7 and 6.4. 

 The plant uses purified water in the boiler, which is converted by the heat of 

combustion into high-pressure steam. Widows Creek employs a contractor-operated portable 

reverse osmosis (RO) system to produce this purified water, using fresh intake water from the 

Tennessee River. The pure water is stored on-site. The contractor hauls the RO resin bed from 

the system off site for regeneration; therefore, there is no wastewater from reverse osmosis 

regeneration processes discharged on site. RO reject water goes to the Unit 1-6 intake. 

5.3 Selective Catalytic Reduction Operation

 During the coal combustion that occurs in the boiler, the nitrogen in the air reacts 

with the oxygen at the elevated temperatures to produce nitrogen oxides (NOx). SCR is a widely 

used practice for the removal of nitrogen oxide from flue gases. For a general description of the 
5

SCR process, see Section 3.2.1.6 of the Interim Detailed Study Report for the Steam Electric 

Power Generating Point Source Category. 

 Widows Creek has SCR systems installed for Units 7 and 8. For Unit 7, the SCR 

system is located downstream of the boiler and upstream of the air preheater, electrostatic 

precipitator (ESP), and the FGD system. For Unit 8, the SCR system is located upstream of the 

air preheater and the FGD system; however, there is no ESP for Unit 8. Because there is no ESP 

for Unit 8, the FGD system removes the fly ash and other particulates from the flue gas. The 

SCR uses ammonia to facilitate converting the NOx in the flue gas to nitrogen and water. Excess 

unreacted ammonia from the SCR system is known as “ammonia slip.” The plant can monitor 

for ammonia slip by analyzing the ash removed from the ESPs because at least part of the 

ammonia will collect on the ash. Widows Creek collects ash samples on a weekly basis during 

ozone season and analyzes them in a laboratory for ammonia to determine the amount of “slip” 

that has occurred. According to the plant, if ammonia slip begins to occur, it may be a sign that 

the catalysts are running out of useful life and may need to be replaced. 

 As the flue gas passes over the catalyst in the SCR process, some of the sulfur 

dioxide is oxidized to sulfur trioxide. Emissions of this sulfur trioxide contribute to the 

formation of acid rain in the environment. To control the formation of sulfur trioxide, Widows 

Creek injects sodium sulfite into the flue gas to remove the sulfur trioxide; however, this addition 

of sodium sulfite can lead to plugging issues in the air preheater. Widows Creek injects the 

sodium sulfite upstream of the air pre-heaters in Unit 7. Widows Creek injects lime into Unit 8. 

 There are no wastewater discharges directly associated with the SCR systems at 

the plant; however, the presence of an SCR can affect the characteristics of the fly ash sluice 

water discharge from the ESP downstream of the SCR. For example, if ammonia slip does occur 

in the system, it is transported with the fly ash to the ash pond. In addition, at Widows Creek, 

ammonia slip can also affect the gypsum slurry discharges from Unit 8, because the FGD system 

acts as the fly ash removal system. Ammonia may also be present in wash water discharges from 

cleaning air preheaters, since ammonia can deposit on preheater surfaces. Most of the fly ash 

sluice water at Widows Creek is recycled after settling, either to the Units 7 and 8 intake and/or 

the FGD makeup water system, discussed later in Section 6.6. Gypsum slurry discharges are 
6

ultimately discharged to the Tennessee River from the gypsum ponds, as discussed in Section 

6.7. Sodium bisulfate/sodium sulfite injection is used in Unit 7 as needed for opacity control. 

These chemicals may be ultimately discharged via the ash pond. 

5.4 Particulate Control

 As described in Section 5.2, ash is generated during the coal combustion process 

and fly ash is transported out of the boiler with the flue gas. Widows Creek utilizes ESPs to 

remove the fly ash from the flue gas emitted from Units 1 through 7. The ESP systems use high 

voltage to generate an electric charge on the particles contained in the flue gas. The charged 

particles then collect on a metal plate with an opposite electric charge. As the particles begin to 

layer on the metal plates, the plates are tapped/rapped to loosen the particles, which fall into a 

collection hopper. The ESPs are the only emission controls on Units 1 through 6; however lowNOx boiler optimization is used to control for NOx emissions and low sulfur coal is burned for 

SO2 emission control. The ESP for Unit 7 is located downstream of the SCR and upstream of 

the FGD scrubber. 

 Widows Creek uses a wet fly ash handling system. The fly ash that is collected 

from the ESP is sluiced from the collection hoppers with some of the intake water and 

transported to the ash pond. The intake water used for sluicing is screened prior to its use; 

however, the plant does not require the water to meet any specific characteristics to be used in 

the sluicing process. 

 Unit 8 does not have a dedicated particulate control system, instead, the FGD 

scrubber system, discussed in Section 5.5, controls the particulates in the flue gas for the unit in 

addition to the sulfur dioxide. The plant is currently investigating the use of an agglomerator for 

additional particulate control on Unit 8. In an agglomerator, some of the particles in the flue gas 

are given a positive charge and some are given a negative charge. The positive and negative 

particles are then attracted to each other, and they clump together forming a larger particle that is 

more easily removed in a particulate control devices (e.g., ESP, FGD scrubber). The 

agglomerator itself does not remove the large particles from the system; however, these larger 

particles can be easily removed from the flue gas using an ESP or other air pollution control 
7

devices, such as the Unit 8 wet FGD scrubber. Plant personnel do not expect any wastewater 

generated from the operation of the agglomerator. In May 2007, Widows Creek began operating 

an agglomerator on one of the Unit 8 FGD modules. Widows Creek is testing and evaluating the 

performance of the agglomerator to determine whether to install it on the other Unit 8 FGD 

modules. 

5.5 FGD System

 The Widows Creek plant operates FGD systems on Units 7 and 8 to control the 

emission of sulfur dioxide from the units. Unit 7 has a spray tower FGD system and Unit 8 has a 

spray tower FGD system using double contact fountain sprays. For a general description of the 

FGD process and the chemical reactions involved, see Section 3.2.1.6 of the Interim Detailed 

Study Report for the Steam Electric Power Generating Point Source Category. 

 The spray tower on Unit 7 utilizes an open vessel, where the absorbent liquid 

(limestone-in-water slurry) is pressurized and sprayed into the vessel through spray nozzles at 

various levels. As the absorbent liquid is sprayed downward into the vessel, and the flue gas 

flows counter-currently to the spray, the absorption of the flue gas sulfur dioxide occurs on the 

droplets of the absorbent. The spray tower FGD system on Unit 7 achieves an 85 to 90 percent 

removal of sulfur dioxide from the flue gas. 

 The spray tower on Unit 8 utilizes an open vessel, where the absorbent liquid 

(limestone-water-slurry) is pressurized and sprayed into the vessel through spray nozzles at the 

bottom of the spray tower at one level. The spray nozzles create a fountain spray. This fountain 

spray tower design creates double contact between the flue gas and droplets of the absorbent. 

This spray tower design achieves 94 to 96 percent removal of sulfur dioxide. In addition to 

removing sulfur dioxide from the flue gas, the scrubber system also removes the fly ash from the 

flue gas in lieu of a precipitator. 

 Both of the FGD systems at Widows Creek use ash pond discharge water or 

Tennessee River water as the water source for the FGD scrubbers. Widows Creek does not 

require the water used in the FGD system to meet any specific characteristics for its use in the 
8

process. In addition, both systems are once-through FGD systems, wherein the gypsum slurry at 

the bottom of the scrubber system is not recycled within the FGD system, but instead is pumped 

directly to the plant’s gypsum ponds. 

 Both of the FGD systems at Widows Creek introduce an air stream to oxidize the 

sulfite product into gypsum, a more useful by-product. Because the FGD system on Unit 8 also 

removes the fly ash from the flue gas, the gypsum slurry discharged from the system contains fly 

ash particulates, as does the resultant gypsum byproduct. Plant personnel noted that because the 

gypsum by-product is not a pure product, it inhibits the sale of the gypsum from Widows Creek. 

5.6 Biofouling Control

 Each of the eight units at Widows Creek uses a once-through cooling system. 

The plant uses water from the Tennessee River and sends it through each of the unit condensers. 

From the condensers, the plant transports the cooling water to a canal that discharges to the 

Tennessee River. The cooling water is screened prior to its use; however, the plant does not 

require the water to meet any specific characteristics to be used in the once-through cooling 

system. 

 The Widows Creek plant does not currently use chlorine or other biocides for 

biofouling control. Instead, the plant has two water boxes for each of the condensers. The plant 

has the capability to backwash one water box while the other is operating. In addition, 

approximately two times a year, the plant uses nylon brushes to clean the condenser tubes. The 

wastewater generated during these cleaning operations is reintroduced into the cooling water 

waste stream and subsequently discharged. 

 

5.7 Metal Cleaning Operation

 Widows Creek has routine outages during the year, during which the plant 

performs maintenance and cleaning of the process equipment. During these scheduled outages, 

the plant may clean the water-side of the boilers with ethylenediaminetetraacetic acid (EDTA) to 

remove scale and deposits from the boiler tubes. The wastewater containing EDTA from the 
9

cleaned boiler tubes is collected in storage tanks. The wastewater is then evaporated in the boiler 

of another operating unit. 

 Widows Creek does not regularly clean the fire-side of the boiler tubes; however, 

when they are cleaned, the plant uses raw river water. After the cleaning process is complete, the 

plant pumps the wastewater to the ash pond. 

6.0 WASTEWATER MANAGEMENT

 Widows Creek generates many different types of wastewater during the operation 

of the coal-fired units. Figure 6-1 presents the wastewater flow diagram for Widows Creek. 

Each of the following wastewaters and their treatment are described in this section of the report: 

y Intake water; 

y Coal pile runoff; 

y Low-volume wastes; 

y Metal cleaning waste; 

y Cooling water; 

y Ash handling water; and 

y FGD system wastewater. 

6.1 Intake Water

 Widows Creek uses water from the Tennessee River as the fresh makeup water to 

the plant. The plant has two separate intake structures, one for Units 1 through 6 and another for 

Units 7 and 8. The intake for Units 1 through 6 is located on a small channel. The intake for 

Units 7 and 8 is located on the river. The intake for Units 7 and 8 includes the recycled ash pond 

effluent, described in Section 6.6; however, the recycle accounts for only 27 MGD of the 725 

MGD withdrawn from the river at this intake. The intake water is screened prior to its use in the 

process. The periodic backwash of the intake screens is collected and discharged to the 

condenser cooling water discharge canal. 
10

Figure 6-1. Wastewater Flow Diagram for Widows Creek 
11

6.2 Coal Pile Runoff

 As discussed in Section 5.1, Widows Creek has two separate coal piles, but only 

one coal pile runoff pond. As rain falls on the coal piles, the runoff from the area becomes 

contaminated with pollutants that are found in the coal. This contaminated wastewater is 

collected in the coal pile runoff pond. Figure B-1, in Appendix B, presents a picture of the coal 

pile runoff pond. The coal pile runoff is allowed to settle and is generally held in these ponds 

until increased rainfall causes the pond to reach overflow levels. At this point, the plant will 

pump some of the coal pile runoff wastewater to the ash pond. 

6.3 Low-Volume Waste

 Widows Creek has several low-volume waste streams generated by the plant. The 

low-volume non-contact cooling water used in some of the plant’s heat exchangers and the 

intake screen backwash are discharged to the condenser cooling water discharge canal, which 

flows directly to the Tennessee River without treatment. Most of the other low-volume wastes 

are collected in the ash pond, which include, but are not limited to, the following: 

y Boiler blowdown; 

y Non-chemical metal cleaning wastewater; 

y Roof and switchyard drainage; 

y Floor wash water; and 

y Miscellaneous cooling water. 

6.4 Metal Cleaning Waste

 The wastewater generated during the fire-side cleaning of the boiler tubes is 

pumped to the ash pond. Water-side boiler tube cleaning wastewater containing EDTA is 

evaporated in the boiler of an operating unit. The condenser tubes are cleaned using nylon 

brushes, as described in Section 5.6, and the water used in the operation is discharged from the 

plant. 

 
12

6.5 Cooling Water

 As discussed in Section 5.6, each of the units at Widows Creek has a oncethrough cooling system. The plant transports the cooling water from the condensers to a 

discharge canal that discharges to the Tennessee River. The once-through cooling water 

represents the largest discharge from the plant. As mentioned in Section 5.6, the plant does not 

use chlorine or other biocides for biofouling control. Instead, the plant backwashes the 

condensers and additionally uses nylon brushes to clean the scale on the condenser tubes. The 

wastewater generated from the condenser backwashing is pumped to the ash pond, but the 

wastewaters generated during the nylon brush cleaning is introduced into the once-through 

cooling water stream and subsequently discharged. 

6.6 Ash Handling Water

 As discussed in Sections 5.2 and 5.4, sluice water is used to collect the bottom ash 

and slag from the bottom of the boiler and the fly ash from the ESP collection hoppers. Widows 

Creek uses water from the Tennessee River as the source of the sluice water. These wastewaters 

are transported to the ash pond; however, the ash sluice water associated with Units 1 through 6 

is transported to a different part of the ash pond than the ash sluice water from Units 7 and 8. 

Because Units 7 and 8 were constructed near the bilge and station sump collection area, which 

discharges to the ash pond, the plant routes the ash sluice from Units 7 and 8 through the bilge 

and station sump collection area. Ultimately, the ash sluice water from Units 1 through 6 is 

combined with the ash sluice water from Units 7 and 8 within the ash pond. 

 The ash pond at Widows Creek covers approximately 340 acres. The wastewater 

that enters the ash pond flows through a long, winding dike created with ash that has been 

dredged from the pond. Figure B-2, in Appendix B, presents a picture of the ash pond dike at 

Widows Creek. As the wastewater flows through the dike, some of the metals and other 

particulates settle to the bottom. The plant continuously removes ash from the pond and stacks it 

in the area surrounding the pond to increase the height of the pond and dike embankments. The 

plant uses a bulldozer to remove the settled ash. The bulldozer operator repeatedly backs into 

the pond and bulldozes the ash out of the pond. After the wastewater travels through the diked 
13

channels, it enters a large open area of the pond. Figure B-3, in Appendix B, presents a picture 

of this open area of the ash pond. 

 During the flow of the wastewater through the diked channels of the ash pond, 

some of this ash water leaches through the embankment of the dike. In addition, some of the 

wastewater in the open area of the ash pond leaches through the banks of the pond. This 

leachate, referred to as “red water” because of its red appearance, is collected by another dike 

surrounding the area and recycled back to the ash pond. 

 Within the open area of the ash pond, the plant uses a series of booms to collect 

floating solids off the top of the wastewater. The floating solids in the water are cenospheres, 

which are formed in the boiler during the coal combustion process. Cenospheres are small, 

lightweight, hollow spheres, and are a naturally-occurring by-product of the combustion process. 

Figure B-4, in Appendix B, presents a picture of the floating cenospheres collected at the bank of 

the ash pond. The hollow portion of these cenospheres is typically filled with air or an inert gas, 

which causes them to float on the water. A contractor periodically comes to the plant and 

removes them from the pond bank and transports them off site for beneficial use. 

 The ash pond wastewater eventually flows to the middle stilling pond, which is 

separated from the ash pond by a dike. At this point, the plant injects carbon dioxide into the 

water to control the pH of the discharge. Because carbon dioxide reacts with water to form 

carbonic acid, the addition of carbon dioxide reduces the pH of the alkaline water. The 

wastewater from this portion of the pond flows into the pumping basin. The pH of the ash pond 

wastewater is typically in the range of 7.0 to 8.5. Widows Creek has a limit of 6.0 to 9.0 for 

Outfall 001 (discharge to the river); therefore, if the pH of the ash pond water is above 9.0, the 

plant injects CO2 to reduce the pH to approximately 7. If Widows Creek is recycling the water 

back to the Unit 7 and 8 intake, there is no upper pH limit for the discharge. 

 Widows Creek has two different outfalls for the ash pond effluent. Typically, the 

plant recycles the ash pond effluent by pumping it to the intake canal for Units 7 and 8, via the 

pumping basin. Figure B-5, in Appendix B, presents a picture of this pumping basin. The 

recycled ash pond effluent typically accounts for only 3.5 percent of the intake water for Units 7 
14

and 8. During excessive rainfall events, the plant may alternatively discharge the ash pond 

effluent directly to the Tennessee River. If the pumping basin begins filling too rapidly, the 

overflow discharge pipes discharge some of the ash pond effluent directly to the Tennessee 

River. According to the plant, the facility uses this outfall one or two times during the year. 

 In addition to the current ash pond described above, Widows Creek originally 

discharged its ash handling wastewater to another pond located on the site. This pond has since 

been filled to capacity with the ash and essentially dried up. This area now has vegetation 

growing over this ash fill. The leachate and the storm water that contacts this area is treated by 

the plant in a constructed wetland. Figure B-6, in Appendix B, presents a picture of the 

constructed wetland cells. The wastewater from the constructed wetland is discharged to the 

Tennessee River. 

6.7 FGD System Wastewater

 As mentioned in the Section 5.5, Widows Creek uses once-through FGD systems; 

therefore, the resulting gypsum slurry from both systems is transported directly to the gypsum 

ponds. Gypsum is a by-product of the FGD process, and is contained in the wastewater 

discharged from the process. For a description of the chemical reactions involved in the FGD 

process, see Section 3.2.1.6 of the Interim Detailed Study Report for the Steam Electric Power 

Generating Point Source Category. 

 The wastewater from this process flows through three gypsum ponds, each one 

fed to the next by gravity. Because the gypsum pond water does not require the pH control that 

the ash pond effluent receives, the wastewater from the final gypsum pond is discharged directly 

to Widows Creek, which flows into the Tennessee River. Figure B-8, in Appendix B, presents a 

picture of the gypsum pond water discharge to Widows Creek. The plant tested the FGD 

wastewater for several metals during the permit renewal process. The metals with the highest 

measured concentrations were magnesium and boron, with concentrations of 360 and 19 mg/L, 

respectively. Selenium was measured at a concentration of 131 ug/L and arsenic was measured 

at 19 ug/L. Mercury was not detected above the detection limit, 0.1 ug/L. The total suspended 

solids long term average concentration was 9.7 mg/L and the daily maximum was 15.4 mg/L. 
15

The flow rate of the FGD slurry into the gypsum ponds was 3.525 MGD and the long term 

average dischare flow was 3.88 MGD, with a daily maximum discharge of 9.09 MGD. 

 As mentioned in Section 5.5, the gypsum slurry generated by the Unit 8 FGD 

system contains fly ash particulate that is removed from the flue gas. The fly ash in the slurry 

also settles to the bottom of the gypsum ponds and is stacked and dewatered with the gypsum. 

The addition of the fly ash to the gypsum gives the gypsum a gray appearance instead of the 

more typical white color. Because the gypsum generated at Widows Creek is essentially 

contaminated with some amount of fly ash, it is not easily marketable. Consequently, the plant 

plans to continue storing the gypsum on site, as described above, until they reach capacity. They 

estimate this onsite storage capacity to last approximately 10 years. 

7.0 REFERENCES

1. U.S. EPA. 2006. Interim Detailed Study Report for the Steam Electric Power 

Generating Point Source Category. EPA-821-R-01-015. Washington, DC. 

November. DCN 01923. 
Appendix A 

LIST OF ATTENDEES 
A-1 

Table A-1. List of Attendees 

Name Organization (Representing) Telephone E

Stanley Bramlett Tennessee Valley Authority John Cook Tennessee Valley Authority Gerald Hemmer Tennessee Valley Authority Joe Jiles Tennessee Valley Authority Lindy Johnson Tennessee Valley Authority (423) 751-3361 lpjohnsoMike Stiefel Tennessee Valley Authority Donna Hill Southern Company (205) 257-5234 dbhill@Paul Chu Electric Power Research Institute Liz Aldridge Hunton & Williams (804) 788-8549 ealdridgKristy Bulleit Hunton & Williams (202) 955-1547 kbulleitJosh Hall EPA/Office of Water (202) 566-1002 hall.joshRon Jordan EPA/Office of Water (202) 566-1003 jordan.rKarrie-Jo Robinson-Shell EPA/Region 4 (404) 562-9308 shell.kaLeslie Churilla ERG (Contractor to EPA) (404) 634-0038 leslie.chT.J. Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.
Appendix B 

PICTURES FROM SITE VISIT
B-1 

Figure B-1. Coal Pile Runoff Pond at Widows Creek 
B-2 

Figure B-2. Ash Pond Dike at Widows Creek 
B-3 

Figure B-3. Ash Pond at Widows Creek 
B-4 

Figure B-4. Cenospheres Collected from the Ash Pond at Widows Creek 
B-5 

Figure B-5. Pumping Basin at Widows Creek 
B-6 

Figure B-6. Constructed Wetland Cells for the Old Ash Pond Runoff at Widows 

Creek 
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Figure B-7. Gypsum Pond at Widows Creek 
B-8 

Figure B-8. Gypsum Pond Discharge to Widows Creek